the oxygen isotope composition petrology and geochemistry of mare basalts evidence for large scale compositional variation in the lunar mantle to investigate the formation and early evolution of the lunar mantle and crust we have analysed the oxygen isotopic composition titanium content and modal mineralogy of a suite of lunar basalts our sample set included eight low ti basalts from the apollo 12 and 15 collections and 12 high ti basalts from apollo 11 and 17 collections in addition we have determined the oxygen isotopic composition of an apollo 15 kreep k potassium ree rare earth element and p phosphorus basalt sample 15386 and an apollo 14 feldspathic mare basalt sample 14053 our data display a continuum in bulk rock delta o 18 values from relatively low values in the most ti rich samples to higher values in the ti poor samples with the apollo 11 sample suite partially bridging the gap calculation of bulk rock delta o 18 values using a combination of previously published oxygen isotope data on mineral separates from lunar basalts and modal mineralogy determined in this study match with the measured bulk rock delta o 18 values this demonstrates that differences in mineral modal assemblage produce differences in mare basalt delta o 18 bulk rock values differences between the low and high ti mare basalts appear to be largely a reflection of mantle source heterogeneities and in particular the highly variable distribution of ilmenite within the lunar mantle bulk delta o 18 variation in mare basalts is also controlled by fractional crystallisation of a few key mineral phases thus ilmenite fractionation is important in the case of high ti apollo 17 samples whereas olivine plays a more dominant role for the low ti apollo 12 samples consistent with the results of previous studies our data reveal no detectable difference between the delta o 17 of the earth and moon the fact that oxygen three isotope studies have been unable to detect a measurable difference at such high precisions reinforces doubts about the giant impact hypothesis as presently formulated

applications of geochemistry in tsunami research a review abstract much progress has been made since the first published studies of tsunami deposits nearly 30 years ago geochemistry is now a much more widely used proxy in tsunami research mainly due to its increasingly recognised value in the identification of historical and or prehistorical deposits at times even providing the conclusive proof when other proxies are missing or equivocal but also its significance in environmental impact assessments following recent tsunamis the rapid advance in analytical techniques has also made it a more approachable and popular method as it is now often faster and cheaper here we provide a review of the applications of geochemistry including the techniques used as well as a database of studies that used chemical proxies in their investigation of recent and old events including onshore and offshore tsunami deposits chemical signatures are often used as markers of marine inundation either as salinity indicators where they can also allow the identification of the limit of tsunami inundation or tracers of the incorporation of marine sourced carbonates their applications as indicators of source material are nevertheless expanding thereby potentially providing additional information on the hydrodynamic processes associated with tsunami inundation although they are largely site specific the effects of post depositional changes in different climatic regimes are examined with a particular emphasis on water leachable components and implications for post event recovery of coastal ecosystems we demonstrate the usefulness of chemical proxies in studies of the geological record of tsunamis extending back thousands of years suggest new approaches and discuss limitations and existing knowledge gaps

experimentally determined si isotope fractionation between silicate and fe metal and implications for earth s core formation abstract stable isotope fractionation amongst phases comprising terrestrial planets and asteroids can be used to elucidate planet forming processes to date the composition of the earth s core remains largely unknown though cosmochemical and geophysical evidence indicates that elements lighter than iron and nickel must reside there silicon is often cited as a light element that could explain the seismic properties of the core the amount of silicon in the core if any can be deduced from the difference in 30 si 28 si between meteorites and terrestrial rocks if the si isotope fractionation between silicate and fe rich metal is known recent studies e g georg r b halliday a n schauble e a reynolds b c 2007 silicon in the earth s core nature 447 31 1102 1106 fitoussi c bourdon b kleine t oberli f reynolds b c 2009 si isotope systematics of meteorites and terrestrial peridotites implications for mg si fractionation in the solar nebula and for si in the earth s core earth planet sci lett 287 77 85 showing sometimes subtle differences between 30 si 28 si in meteorites and terrestrial rocks suggest that si missing from terrestrial rocks might be in the core however any conclusion based on earth meteorite comparisons depends on the veracity of the 30 si 28 si fractionation factor between silicates and metals at appropriate conditions here we present the first direct experimental evidence that silicon isotopes are not distributed uniformly between iron metal and rock when equilibrated at high temperatures high precision measurements of the silicon isotope ratios in iron silicon alloy and silicate equilibrated at 1 gpa and 1800 c show that si in silicate has higher 30 si 28 si than si in metal by at least 2 0 these findings provide an experimental foundation for using isotope ratios of silicon as indicators of terrestrial planet formation processes they imply that if si isotope equilibrium existed during segregation of earth s core forming metal and silicate mantle there should be an isotopic signature of si in the core our experiments combined with previous measurements of si isotope ratios in meteorites and rocks representing the bulk silicate earth suggest that the formation of the earth s core imparted a high 30 si 28 si signature to the bulk silicate earth due to dissolution of 6 wt si into the early core

quarrying transport and deposition of cliff top storm deposits during extreme events banneg island brittany abstract on 10 march 2008 a particularly high energy storm hit the french atlantic coast and the western part of the english channel this storm did not generate exceptionally high waves significant and maximum wave heights recorded in the iroise sea brittany reached 10 85 and 18 17 m respectively whereas during the 1989 90 winter storms they had reached 12 and 20 m respectively the exceptional character of the march 2008 storm event arises from the fact that it occurred during an exceptional spring tide from a morphogenetic point of view the effects of this storm in terms of block quarrying transport and deposition on banneg island brittany were significant this study shows that the weight of the blocks displaced during the event was between 0 07 and 42 64 t with a median value of 0 72 t more than 60 of the blocks were quarried from the wave scoured cliff top platform demonstrating that the favoured zone for supplying material was located inland of the cliff two dominant modes of transport were involved depending on the relationship between extreme water levels and cliff height at the centre of the island the height of the waves breaking over the top of the cliffs on the western coast resulted in a torrential surge that flowed out towards the eastern coast of the island over a landward sloping platform on the western coast of the island blocks weighing between 0 3 and 1 4 t were displaced between 50 and 90 m from the cliff edge by this flow at the flow outlet on the eastern coast 90 m from the western cliff edge a pit 1 6 m deep was excavated at porz ar bagou cove and some of the mobilised blocks were deposited in two parallel lobes about 40 m seaward of the eastern shoreline elsewhere on the island block transport occurred by airborne projection although wave heights were lower than the altitude of the cliffs the pressure exerted by breaking waves on the bedrock was sufficient to quarry and displace blocks a temporal comparison of the changes recorded in the double and triple boulder ridges showed that the most seaward ridges were practically untouched with the most important changes occurring in the second and third ridges these observations allow us to propose a spatio temporal model for the accretion of cliff top storm deposits ctsds with the various stages of ctsd formation being directly related to the morphological evolution of the cliff

the proto earth as a significant source of lunar material geochemical evidence continues to challenge giant impact models which predict that the moon formed from both proto earth and impactor material analyses of lunar samples reveal isotopic homogeneity in titanium a highly refractory element suggesting lunar material was derived predominantly from the mantle of the proto earth

oxygen isotope studies of achondrites abstract oxygen isotope abundances provide a powerful tool for recognizing genetic relationships among meteorites among the differentiated achondrites three isotopic groups are recognized l snc mars 2 earth and moon and 3 hed howardites eucrites diogenites the hed group also contains the mesosiderites main group pallasites and silicates from iiiab irons the angrites may be marginally resolvable from the hed group within each of these groups internal geologic processes give rise to isotopic variations along a slope 1 2 fractionation line as is well known for terrestrial materials variations of 17o from one planet to another are inherited from the inhomogeneities in the solar nebula as illustrated by the isotopic compositions of chondrites and their constituents among the undifferentiated achondrites five isotopic groups are found 1 aubrites 2 winonaites and iab iiicd irons 3 brachinites 4 acapulcoites and lodranites and 5 ureilites the isotopic compositions of aubrites coincide with the earth and moon and also with the enstatite chondrites these bodies apparently were derived from a common reservoir the isotopic composition of which was established at the chondrule scale by nebular processes isotopic similarities between chondrites and achondrites are seen only for the following instances 1 enstatite chondrites and aubrites 2 h chondrites and he irons and 3 l or ll chondrites and iva irons the isotopic data also support the following genetic associations 1 winonaites and iab iiicd irons 2 acapulcoites and lodranites and 3 ureilites and dark inclusions of c3 chondrites an attempt to reconcile the whole planet isotopic compositions of earth mars and the eucrite parent body with mixing models of their chemical compositions failed it is not possible to satisfy both the chemical and isotopic compositions of the terrestrial planets using known primitive solar system components

major storm periods and climate forcing in the western mediterranean during the late holocene abstract big storm events represent a major risk for populations and infrastructures settled on coastal lowlands in the western mediterranean where human societies colonized and occupied the coastal areas since the ancient times the variability of storm activity for the past three millennia was investigated with a multi proxy sedimentological and geochemical study from a lagoonal sequence mappings of the geochemistry and magnetic susceptibility of detrital sources in the watershed of the lagoon and from the coastal barriers were undertaken in order to track the terrestrial or coastal marine origin of sediments deposited into the lagoon the multi proxy analysis shows that coarser material low magnetic susceptibility and high strontium content characterize the sedimentological signature of the paleostorm levels identified in the lagoonal sequence a comparison with north atlantic and western mediterranean paleoclimate proxies shows that the phases of high storm activity occurred during cold periods suggesting a climatically controlled mechanism for the occurrence of these storm periods besides an in phase storm activity pattern is found between the western mediterranean and northern europe spectral analyses performed on the sr content revealed a new 270 year solar driven pattern of storm cyclicity for the last 3000 years this 270 year cycle defines a succession of ten major storm periods sp with a mean duration of 96 54 yr periods of higher storm activity are recorded from 680 to 560 cal yr bc sp10 end of the iron age cold period from 140 to 820 cal yr ad sp7 to sp5 with a climax of storminess between 400 and 800 cal yr ad dark ages cold period and from 1230 to 1800 cal yr ad sp3 to sp1 little ice age periods of low storm activity occurred from 560 cal yr bc to 140 cal yr ad sp9 and sp8 roman warm period and from 820 to 1230 cal yr ad sp4 medieval warm period

paleoclimatic forcing of magnetic susceptibility variations in alaskan loess during the late quaternary visual matches and statistical tests suggest correlations between marine isotope curves retrodictive solar insolation at lat 65 n and magnetic susceptibility profiles through late quaternary age alaskan loess sections the susceptibility changes largely appear to reflect variability in magnetite content due to climatically controlled changes in wind intensity and competence magnetic susceptibility profiles through massive loess can provide stratigraphic context for intercalated paleosols and tephras a prominent paleosol correlated with marine isotope stage 5 occurs several metres above the old crow ash in loess sections indicating that this important tephra is older than suggested by thermoluminescence dates and may have been deposited ca 215 25 ka

iron isotope differences between earth moon mars and vesta as possible records of contrasted accretion mechanisms the iron isotope compositions of shergotty nakhla chassigny snc meteorites thought to come from mars eucrites and diogenites assumed to sample asteroid 4 vesta and rocks from the moon and earth have been measured using high precision plasma source mass spectrometry the means of eight samples from mars and nine samples from vesta are within error identical despite a range of rock types they are lighter by 0 1 in 57fe 54fe compared to the average of 13 terrestrial mantle derived rocks the latter value is identical within uncertainty with a previously published mean of 46 igneous rocks from the earth the average for 14 lunar basalts and highland plutonic rocks covering a broad spectrum of major element composition is heavier by 0 1 in 57fe 54fe relative to our estimate for the earth s mantle and therefore 0 2 heavier than the eucrites diogenites and snc meteorites however the data scatter somewhat and the apollo 15 green glass and apollo 17 orange glass are identical to samples from mars and vesta there is no clear relationship between petrological characteristics and fe isotope composition despite a wide spectrum of samples instead contrasted planetary isotopic signatures are clearly resolved statistically after evaluating alternative scenario it appears that the most plausible explanation for the heavier fe in the earth and moon is that both objects grew via processes that involved partial vaporisation leading to kinetic iron isotope fractionation followed by minor loss this is consistent with the theory in which the moon is thought to have originated from a giant impact between the proto earth and another planet combined with numerical simulations fe isotope data can offer the potential to provide constraints on the processes that occurred in planetary accretion

late holocene post 4000 years bp coastal dune development in northumberland northeast england the recent environmental history of coastal dune systems in northumberland northeast england has been examined using geomorphological stratigraphical and sedimentological techniques linked to radiocarbon and infrared stimulated luminescence irsl dating stratigraphies were determined from 22 vibracores and three sections and dune chronology was based on 28 14 c dates from peat and soil organic horizons and 26 irsl dates on k feldspar grains from within sand layers almost all dune systems are associated with regressive shorelines consequent upon a fall in relative sea level rsl from its holocene peak and indicate rsl functioned as a macroscale control on dune development where dunes are anchored on terrestrial sediment dune expansion may have been either transgressive or regressive in nature where near shore marine sediments form the dune substrate a regressive prograding dune model seems most likely most dune building occurred during the little ice age lia probably in a

cliff top storm deposits on banneg island brittany france effects of giant waves in the eastern atlantic ocean this study is based on the morphosedimentary analysis of the cliff top storm deposits accumulated on the coast of banneg island located in the archipelago of molene brittany france these ctsds comprise large tabular clasts quarried from the upper part of the cliff and the backing scoured platform by giant oceanic storm waves impacting directly the western coast of the island an analysis of the distribution and the geomorphology of these accumulations were carried out using the dgps topographic surveys most of the clasts are organised into imbricate boulder clusters or ridges deposited between 7 5 and 14 5 masl 52 accumulations were inventoried from the north to the south of the island representing a global volume of 1000 m3 the median size of the clasts calculated is equivalent to 0 8 0 6 0 4 m and a weight of 0 6 t the largest one measuring 5 3 3 9 0 5 m 32 t is located in the centre of the island ridge 28 it has been deposited 14 m inland from the edge of the cliff at the elevation of 9 m sediment analysis shows that clast sizes become smaller with increasing distance from the shoreline but there is no relationship between the sorting and the distance inland a study of the hydrodynamic conditions inducing clast transport was undertaken by an analysis of the wave data from the 1989 to the 1990 winter storms models of wave runup indicate that their highest water levels may have reached up to 19 masl 5 to 10 m higher than the top of the cliff submersion by giant storm waves has been more important and frequent in the centre and the south of the island wave data over the 1979 to the 2007 period shows that no events as powerful as those of the 1989 to the 1990 winter were recorded during the last 30 years yet it appears that the 1979 1990 decade was characterized by important morphogeneous events while the following period 1990 2007 has experienced a sharp decrease in storm events these variations could be attributed to the inversion from a negative towards a positive phase in the north atlantic oscillation index

morphodynamic evolution of a coastal lagoon entrance during swash overwash new field observations of beach berm growth resulting in the sub aerial closure of an intermittently closed and open lake or lagoon are presented these perched estuarine systems frequently exhibit ephemeral entrances that respond to process forcing almost instantaneously on a geomorphic timescale with closure by a supra tidal berm of depositional origin the observations were made following a mechanical opening of the entrance and show very rapid vertical growth of an initially low beach berm as a result of swash overtopping and sediment overwash very little simultaneous seaward progradation was observed sediment overwash volumes were obtained from survey data over a period of 12 days either side of spring tide and the observations also provide an accurate measure of swash sediment transport at the berm crest a process based parametric model is developed through robust parameterisations of wave run up wave run up distributions and sediment transport and is applied to predict the total overwash transport into and infilling the estuary entrance the model is tested against the field data and compares well with the observations while the field data are site specific the proposed modelling framework represents a first step in modelling the complex growth and recovery of natural beach berms in broad scale morphodynamic models

late quaternary sea level changes crustal movements and coastal evolution in northumberland uk northumberland lies in the transition between holocene emergence and submerg ence and is thus a critical zone for testing models of isostatic rebound we have collected data from this area to reconstruct relative sea level changes and lateral coastline movements for the last 14000 y these are deposits from tidal marsh back barrier wetland and terrestrial environ ments producing 47 sea level index points from 12 sites there is no unequivocal evidence for late devensian sea levels above present and the reliable sea level index points are restricted between 26 m and 12 5 m relative to present and 9 0 2 5 kyr cal bp analysis of these quantifies differential responses to glacio and hydroisostatic rebound with the northern sites recording a mid holocene sea level maximum ca 2 5 m above present whereas the southern sites show a maximum ca 0 5 m above present these observations show a reasonable fit with the predictions from quantitative models of glacio and hydroisostatic rebound but there is currently no unique solution of earth and ice model parameters that will explain all the sea level observations copyright 2000 john wiley sons ltd

spectrocolorimetric interpretation of sedimentary dynamics the new q7 4 diagram colour is a fundamental property of sediment and is often used for lithographic description to determine sedimentological structures facies etc however the sedimentary information contained in this parameter is difficult to extract because it is difficult to quantify colour can be quantified by spectrocolorimetry which provides very high resolution data quickly and non destructively when adapted to sedimentology spectrocolorimeters prove to be powerful tools due to their low purchase and maintenance costs and some are portable and easily used in the field several methods have been used to extract sedimentological data from colorimetric spectra first derivatives factorial analysis etc in the present study we first provide a review of the sedimentological application of spectrophotometers and after having described these methods their advantages and disadvantages we then describe a new tool called the q7 4 diagram abscissa l ordinates 700 400 ratio this new technique permits sedimentological units to be defined allows the identification of different sediment components and provides 5 distinct poles clayey deposits organic rich deposits chlorophyll a and by products altered organic matter deposits iron rich deposits carbonated deposits coupled with the analysis of first derivative spectra it is possible to distinguish different pigments linked to the degradation and or nature of the organic material chlorophyll a melanoidin etc the state of iron oxidation for example hematite and goethite like signatures and the nature of clays the q7 4 diagram permits rapid acquisition of high resolution data on changes of sediment dynamics in geosystems that have been subjected to highly varied climatic environmental conditions the instrument is non destructive easy to use and maintain portable for use in the field fast to implement is capable of high resolution and has a vast range of possible applications spectrocolorimetry appears to provide many advantages and could become an essential and robust tool for preliminary sedimentological studies

storminess control over african dust input to the moroccan atlantic margin nw africa at the time of maxima boreal summer insolation a record of the last 220 kyr abstract precessional forcing of dust flux from northwest africa to the atlantic during the last 220 kyr is recognised through changes in physical and chemical sediment properties sediment colour reflectance magnetic susceptibility x ray fluorescence element intensity in a core from the moroccan margin sediment colour reflectance magnetic susceptibility and ca and fe element intensity changes are thought to be driven by dust input from north africa spectral analysis of the sediment properties records displays a dominant periodicity in the 1 23 kyr 1 frequency band that is associated with the earth s orbital precession peaks in terrigenous supply match precessional minima this suggests a close link between maxima of boreal summer solar radiation monsoon activity and dust generation enhanced precession driven solar radiation would have caused increased seasonal temperature contrasts which amplified atmospheric turbulence and stimulated storminess such a scenario is similar to today s summer conditions when frequent storms cause distinct dust plumes to form in the area and transport fine terrigenous material to the adjacent north atlantic ocean

correlating three centuries of historical and geological data for the marine deposit reconstruction of two depositional environments of the french atlantic coast this paper details a high resolution record of french atlantic coast extreme wave events using a multi proxy analysis of dated sedimentary deposits two lagoons 1 the petite mer de g vres and 2 the traicts du croisic were chosen to identify damaging storm events from the last 300 years with beeker sampling 210pb and 137cs dating and sedimentary analysis using two new geochemical proxies in the french atlantic coast sr fe and ca ti shows that several storminess events are reported in the nine cores drilled by correlation with historical archives seven major storms are confirmed 1924 ce 1940 ce 1972 ce 1977 ce 1990 ce 1999 ce and an 1896 ce highly damaging event four other xixth and xviiith century extreme wave event correlations are also proposed from this multi proxy analysis 1775 ce 1811 ce 1838 ce and 1876 ce societal and natural impacts caused by these coastal floods are revealed using our dense and varied historical archives

isotopes as tracers of the sources of the lunar material and processes of lunar origin ever since the apollo programme isotopic abundances have been used as tracers to study lunar formation in particular to study the sources of the lunar material in the past decade increasingly precise isotopic data have been reported that give strong indications that the moon and the earth9s mantle have a common heritage to reconcile these observations with the origin of the moon via the collision of two distinct planetary bodies it has been proposed i that the earth moon system underwent convective mixing into a single isotopic reservoir during the approximately 10 3 year molten disc epoch after the giant impact but before lunar accretion or ii that a high angular momentum impact injected a silicate disc into orbit sourced directly from the mantle of the proto earth and the impacting planet in the right proportions to match the isotopic observations recently it has also become recognized that liquid vapour fractionation in the energetic aftermath of the giant impact is capable of generating measurable mass dependent isotopic offsets between the silicate earth and moon rendering isotopic measurements sensitive not only to the sources of the lunar material but also to the processes accompanying lunar origin here we review the isotopic evidence that the silicate earth moon system represents a single planetary reservoir we then discuss the development of new isotopic tracers sensitive to processes in the melt vapour lunar disc and how theoretical calculations of their behaviour and sample observations can constrain scenarios of post impact evolution in the earliest history of the earth moon system

turbulent mixing of metal and silicate during planet accretion and interpretation of the hf w chronometer in the current view of planet formation the final assembly of the earth involved giant collisions between proto planets 1000 km radius with the moon formed as a result of one such impact at this stage the colliding bodies had likely differentiated into a metallic core surrounded by a silicate mantle during the moon forming impact nearly all metal sank into the earth s core we investigate to what extent large self gravitating iron cores can mix with surrounding silicate and how this influences the short lived chronometer hf w used to infer the age of the moon we present fluid dynamical models of turbulent mixing in fully liquid systems attempting to place constraints on the degree of mixing erosion of sinking cores driven by rayleigh taylor instability does lead to intimate mixing and equilibration but large blobs 10 km diameter do not emulsify entirely emulsification is enhanced if most of the accreting metal cores deform into thin structures during descent through the earth s mantle yet only 1 20 of earth s core would equilibrate with silicate during earth s accretion the initial speed of the impactor is of little importance we proceed to evaluate the mixing potential for shear instabilities where silicate entrainment across vertical walls causes mixing the turbulent structure indicates that vortices remain at the largest scale and do not mix to centimeter length scale where diffusion operates and isotopes can equilibrate thus incomplete emulsification and equilibration of accreting iron cores is likely to occur the extent of metal silicate equilibration provides key information for interpretation of siderophile budgets and the timing of core formation using the hf w chronometer the time scale of core formation derived from the hf w chronometer is usually tied to the last major metal silicate re equilibration believed to coincide with time of the moon forming impact however we show that large cores have limited ability to reset the hf w system in the silicate earth excess 182 w in bulk silicate earth is more sensitive to early core formation processes than to radiogenic ingrowth after the last giant impact

chemical signatures of palaeotsunamis a forgotten proxy article i nfo article history a range of diagnostic criteria are required to help identify palaeotsunami deposits although chemical signatures have long been used as indicators of palaeosalinity in sedimentary sequences their use in the studies of palaeotsunami deposits is rarely applied and is yet to be widely recognised the chemical composition of interstitial water in coastal ponds and sedimentary sequences in coastal marshes and lagoons has been used successfullyasanindicatoroftsunamiinundation chemicalsignaturescanalsoprovidecluesaboutthelandward limit of runup of a tsunami beyond the area of sediment deposition like most palaeotsunami proxies however the preservation of chemical signatures varies with environmental conditions

storminess and vulnerability along the atlantic coastlines of europe analysis of storm records and of a greenhouse gases induced climate scenario abstract identification of the distinctive circulation patterns of storminess on the atlantic margin of europe forms the main objective of this study dealing with storm frequency intensity and tracking the climatology of the extratropical cyclones that affect this region has been examined for the period 1940 1998 coastal meteorological data from ireland to spain have been linked to the cyclone history for the north atlantic in the analysis of storm records for european coasts the study examines the evolution in the occurrence of storms since the 1940s and also their relationship with the north atlantic oscillation nao results indicate a seasonal shift in the wind climate with regionally more severe winters and calmer summers established this pattern appears to be linked to a northward displacement in the main north atlantic cyclone track an experiment with the echam4 a gcm at high resolution t106 has also been used to model the effect of a greenhouse gases induced warming climate on the climatology of coastal storms in the region the experiment consists of 1 a 30 year control time slice representing present day equivalent co 2 concentrations and 2 a 30 year perturbed period corresponding to a time when the radiative forcing has doubled in terms of equivalent co 2 concentrations the boundary conditions have been obtained from an atmosphere ocean coupled oa gcm simulation at low horizontal resolution an algorithm was developed to allow the identification of individual cyclone movements in selected coastal zones for most of the northern part of the study region covering ireland and scotland results describe the establishment by ca 2060 of a tendency for fewer but more intense storms the impacts of these changes in storminess for the vulnerability of european atlantic coasts are considered for low lying exposed and soft sedimentary coasts as in ireland these changes in storminess are likely to result in significant localised increases in coastal erosion

lake sediment record of late holocene hurricane activities from coastal alabama coastal lake sediments contain a stratigraphically and chronologically distinct record of major hurricane strikes during late holocene time frederic a category 3 hurricane that struck the alabama coast on the gulf of mexico in 1979 left a distinct sand layer in the nearshore sediments of lake shelby as a result of storm tide overwash of beaches and dunes sediment cores taken from the center of lake shelby contain multiple sand layers suggesting that major hurricanes of category 4 or 5 intensity directly struck the alabama coast at ca 3 2 3 0 2 6 2 2 1 4 and 0 8 ka 14 c yr with an average recurrence interval of 600 yr the alabama coast is likely to be struck by a category 4 or 5 hurricane within the next century

turbulent metal silicate mixing fragmentation and equilibration in magma oceans abstract much of the earth was built by high energy impacts of planetesimals and embryos many of these impactors already differentiated with metallic cores of their own geochemical data provide critical information on the timing of accretion and the prevailing physical conditions but their interpretation depends critically on the degree of metal silicate chemical equilibration during core mantle differentiation which is poorly constrained efficient equilibration requires that the large volumes of iron derived from impactor cores mix with molten silicates down to scales small enough to allow fast metal silicate mass transfer here we use fluid dynamics experiments to show that large metal blobs falling in a magma ocean mix with the molten silicate through turbulent entrainment with fragmentation into droplets eventually resulting from the entrainment process in our experiments fragmentation of the dense fluid occurs after falling a distance equal to 3 4 times its initial diameter at which point a sizable volume of ambient fluid has already been entrained and mixed with the dense falling fluid contrary to previous assumptions we demonstrate that fragmentation of the metallic phase into droplets may not be required for efficient equilibration turbulent mixing by drastically increasing the metal silicate interfacial area may result in fast equilibration even before fragmentation efficient re equilibration is predicted for impactors of size small compared to the magma ocean depth in contrast much less re equilibration is predicted for large impacts in situations where the impactor core diameter approaches the magma ocean thickness

ancient sedimentary dna reveals past tsunami deposits abstract palaeotsunami deposits are the primary sources of information on past large tsunami events and thereby are critical for earthquake and tsunami hazard assessments they usually form sandy layers preserved in coastal sediments and contain indicators of marine origins such as microfossils e g diatoms and foraminifera and geochemical signals of saltwater however these indicators are often modified or erased with time to address this issue we present the first application of a palaeogenetic approach to a series of up to approximately 2000 year old sandy palaeotsunami deposits from a coastal wetland on hokkaido island japan we found the dna of marine foraminiferal species preserved in palaeotsunami deposits in the absence of foraminifera tests the recovery and analysis of the ancient sedimentary dna of marine organisms preserved in coastal zone sediments for millennia represents a new and promising tool for the identification of past tsunamis

si isotope systematics of meteorites and terrestrial peridotites implications for mg si fractionation in the solar nebula and for si in the earth s core abstract high precision si isotope ratios have been measured for a series of meteorites and terrestrial samples using high resolution multi collector icp ms our results differ from those reported in an earlier study georg et al 2007 si in the earth s core nature 447 1102 1106 in two important aspects first our data set reveals systematic differences in 30 si between different chondrite groups that are correlated with their mg si elemental ratio second in agreement with the previous study 30 si for the terrestrial samples are higher than values for chondrites but the difference between the bulk silicate earth bse and the carbonaceous chondrites 30 si bse c arbonaceous chondrites 0 08 0 04 1 standard deviation is about a factor of 2 smaller than previously reported the 30 si versus mg si trend defined by the chondrite groups can be explained by reaction of olivine with a sio rich vapor to form enstatite starting from a carbonaceous chondrite composition in contrast the difference between the bse and carbonaceous chondrites must reflect a different process and can be explained by incorporation of si into the earth s core during metal silicate equilibration in a deep magma ocean the observed si isotope fractionation is consistent with the temperatures and pressures of metal silicate equilibration derived from siderophile element abundances in the earth s mantle

evidence for a change in the periodicity of tropical climate cycles at 2 4 myr from whole core magnetic susceptibility measurements the earth s orbit about the sun is influenced by gravitational interactions with the moon and other planets the resulting orbital perturbations give rise to cyclical variations in orbital eccentricity obliquity and precession with periods of 100 41 19 and 23 kyr respectively1 these variations are climatically important because they affect the seasonal and latitudinal distribution of solar radiation magnetic susceptibility measurements in deep sea sediment cores can be used as a sensitive indicator of temporal variations in the concentration of terrigenous material supplied to the sea bed here we use this approach to study the evolution of cycles of terrigenous sedimentation at ocean drilling program sites in the arabian sea and the eastern tropical atlantic we show from spectral analyses of the two susceptibility time series spanning the past 3 2 3 5 myr that the records are driven strongly by orbital forcing before 2 4 myr before present bp both records are strongly influenced by the 23 and 19 kyr periodicities but after 2 4 myr they are both significantly influenced by the 41 kyr periodicity this shift coincides with the beginning of major northern hemisphere glaciation which indicates for the indian ocean site that the supply of terrigenous sediment carried by monsoonal winds has responded to the rapid increase in ice cover at this time we cannot however exclude possible effects of changes in bottom water circulation on the susceptibility record of the atlantic site

zinc isotopic evidence for the origin of the moon lunar magmatic rocks are shown to be enriched in the heavy isotopes of zinc and to have lower zinc concentrations than terrestrial or martian igneous rocks these variations represent the large scale evaporation of zinc most probably in the aftermath of the moon forming giant impact event the heavily favoured theory for the origin of the earth moon system is a giant impact between the proto earth and a mars sized body such a cataclysmic event would have left its mark on the isotopic composition of the moon because light isotopes evaporate more readily than heavier ones zinc in particular is a powerful indicator of the volatile histories of planets it undergoes strong isotopic fractionation in planetary rocks but is hardly fractionated following volcanic activity on earth this study compares high precision zinc isotopic data for lunar basalts martian meteorites and terrestrial igneous rocks and finds that lunar magmatic rocks are enriched in the heavy isotopes of zinc and have lower zinc concentrations than terrestrial or martian samples the authors conclude that these variations are the result of large scale evaporation of zinc in the aftermath of the moon forming giant impact event volatile elements have a fundamental role in the evolution of planets but how budgets of volatiles were set in planets and the nature and extent of volatile depletion of planetary bodies during the earliest stages of solar system formation remain poorly understood1 2 the moon is considered to be volatile depleted and so it has been predicted that volatile loss should have fractionated stable isotopes of moderately volatile elements3 one such element zinc exhibits strong isotopic fractionation during volatilization in planetary rocks4 5 but is hardly fractionated during terrestrial igneous processes6 making it a powerful tracer of the volatile histories of planets here we present high precision zinc isotopic and abundance data which show that lunar magmatic rocks are enriched in the heavy isotopes of zinc and have lower zinc concentrations than terrestrial or martian igneous rocks conversely earth and mars have broadly chondritic zinc isotopic compositions we show that these variations represent large scale evaporation of zinc most probably in the aftermath of the moon forming event rather than small scale evaporation processes during volcanism our results therefore represent evidence for volatile depletion of the moon through evaporation and are consistent with a giant impact origin for the earth and moon

lagoon subsidence and tsunami on the west coast of new zealand abstract sediment core and trench data from a coastal lagoon on the west coast of the south island new zealand are used to investigate evidence for co seismic subsidence and associated tsunami inundation physical data are used to document a salt marsh soil buried 80 cm below the modern sediment surface that is locally covered by a gravelly sand bed the sediment record also contains geochemical and biological diatom and foram evidence for abrupt changes in salinity of lagoon waters that link to subsidence tsunami flooding and to the open versus closed state of the lagoon tidal entrance at the local scale these relationships allow for separation of tsunami evidence from other agents of environmental change in the lagoon we also propose a conceptual connection between these local changes and regional drivers of landscape development most notably major earthquakes and resultant pulses in sediment supply to the coast

forming a moon with an earth like composition via a giant impact in the giant impact theory the moon formed from debris ejected into an earth orbiting disk by the collision of a large planet with the early earth prior impact simulations predict that much of the disk material originates from the colliding planet however earth and the moon have essentially identical oxygen isotope compositions this has been a challenge for the impact theory because the impactor s composition would have likely differed from that of earth we simulated impacts involving larger impactors than previously considered we show that these can produce a disk with the same composition as the planet s mantle consistent with earth moon compositional similarities such impacts require subsequent removal of angular momentum from the earth moon system through a resonance with the sun as recently proposed

contamination of tsunami sediments in a coastal zone inundated by the 26 december 2004 tsunami in thailand tsunami sediments deposited in a coastal zone of thailand by the 26 december 2004 tsunami wave were sampled within 50 days after the event all surface and ground waters in tsunami inundated zone revealed significant salinity at that time the tsunami sediments composed mainly of fine to medium sand contain significantly elevated contents of salts na k ca 2 mg 2 cl and so4 2 in water soluble fraction and of cd cu zn pb in the bioavailable fraction and as in the exchangeable fraction in relation to the reference sample the origin of contaminants is marine as well as litho and anthropogenic the salts and pb zn and cu reveal high correlation to each other and to the mean grain size pore size and porosity serious environmental hazard exists in that region because due to gentle morphology there is a risk of migration of the contaminants into ground waters and food chain

chemical fractionation in the silicate vapor atmosphere of the earth despite its importance to questions of lunar origin the chemical composition of the moon is not precisely known in recent years however the isotopic composition of lunar samples has been determined to high precision and found to be indistinguishable from the terrestrial mantle despite widespread isotopic heterogeneity in the solar system in the context of the giant impact hypothesis this level of isotopic homogeneity can evolve if the proto lunar disk and post impact earth undergo turbulent mixing into a single uniform reservoir while the system is extensively molten and partially vaporized in the absence of liquid vapor separation such a model leads to the lunar inheritance of the chemical composition of the terrestrial magma ocean hence the turbulent mixing model raises the question of how chemical differences arose between the silicate earth and moon here we explore the consequences of liquid vapor separation in one of the settings relevant to the lunar composition the silicate vapor atmosphere of the post giant impact earth we use a model atmosphere to quantify the extent to which rainout can generate chemical differences by enriching the upper atmosphere in the vapor and show that plausible parameters can generate the postulated enhancement in the feo mgo ratio of the silicate moon relative to the earth s mantle moreover we show that liquid vapor separation also generates measurable mass dependent isotopic offsets between the silicate earth and moon and that precise silicon isotope measurements can be used to constrain the degree of chemical fractionation during this earliest period of lunar history an approach of this kind has the potential to resolve long standing questions on the lunar chemical composition

large scale washover sedimentation in a freshwater lagoon from the southeast australian coast sea level change tsunami or exceptionally large storm 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 on the southeast australian coast coring of the deposit suggests it extends continuously up to 600 m inland and tapers landward rising to 1 6 m above principle datum in places the sand is overlain by accumulations of organic rich silt that contain charophytes indicating re estab lishment of lagoon conditions hypotheses considered for the deposition of the sandsheet are higher holocene sea level storms and tsunami ground penetrating radar transects of the seaward dune system suggest a penecontemporaneous erosional contact between a series of truncated pre event dunes and several small over lying post event dunes dating the sandsheet was problematic but it is confined to the last 800 years the young age combined with a lack of associated beach deposits and evidence of wave scouring suggest that a higher sea level hypothesis is unlikely this sand lens is attributed to a large scale washover event from the southeast based on comparisons with modern storm deposits from the same coast and sedimentological diagnostic crite ria derived from studies of modern storm and tsunami deposited sandsheets it is concluded that this sand deposit is the product of a short lived large scale overwash event attributed to a late holocene tsunami

calibrating a sedimentary record of overwash from southeastern new england using modeled historic hurricane surges we present a 2000 year record of overwash deposits preserved in a backbarrier salt marsh from southeastern new england the timing of recent deposits matches well with large hurricane induced storm surge events documented by local tide gauges in 1991 1960 1954 and 1938 storm surge modeling is used to evaluate the flooding history at the site as well as to assess the pre instrumental historical record storms in 1815 1727 and 1635 likely caused significant surge that overtopped the barrier with the timing of coarse grained overwash deposition correlating well with these events we infer that twenty three prehistoric layers mapped across the site were likely also deposited by landfalling hurricanes additional records from the area will help to evaluate whether or not temporal trends at the site are a robust representation of hurricane activity for the region the frequency of overwash at mattapoisett marsh on average 1 5 events per century is significantly higher than many other overwash based reconstructions from the western north atlantic further the mattapoisett marsh record does not contain significant multi centennial gaps in overwash layers this initial comparison of the data from mattapoisett marsh with other reconstructions from the western north atlantic may point toward relatively constant tropical cyclone frequency over the last 2000 years with significant variation in the number of intense tropical cyclones

sedimentology and geochemistry of thermokarst ponds in discontinuous permafrost subarctic quebec canada 1 thermokarst thaw ponds and lakes are distributed throughout arctic and subarctic regions however their natural variability and temporal evolution recorded in the bottom sediments are poorly understood this paper presents a multiproxy study conducted in a subarctic site with many thermokarst ponds near kuujjuarapik whapmagoostui on the eastern shore of hudson bay sedimentological geochemical and chronological analyses have been performed on short sediment cores 10 20 cm retrieved from limnologically contrasted ponds analyses revealed two distinct sedimentary facies from bottom to top 1 massive marine silts and clays deposited during postglacial tyrrell sea transgression ca 8000 to 6000 cal yr bp subsequently emerged by glacio isostatic rebound and more recently ca 1500 to 400 cal yr bp affected by permafrost inception and growth 2 laminated organic rich lacustrine muds deposited since permafrost thawing and subsidence i e since thermokarst pond inception the last centuries despite displaying strikingly different water colors the study ponds showed similar long term developmental patterns regarding their physico chemical properties as recorded in the sediments such as decreasing mineral grain size from silts to clays decreasing major chemical element concentrations increasing organic matter content and decreasing bottom water oxygen concentrations from well oxygenated to anoxic hypoxic conditions

7000 years of paleostorm activity in the nw mediterranean sea in response to holocene climate events abstract a high resolution record of paleostorm events along the french mediterranean coast over the past 7000 years was established from a lagoonal sediment core in the gulf of lions integrating grain size faunal analysis clay mineralogy and geochemistry data with a chronology derived from radiocarbon dating we recorded seven periods of increased storm activity at 6300 6100 5650 5400 4400 4050 3650 3200 2800 2600 1950 1400 and 400 50 cal yr bp in the little ice age in contrast our results show that the medieval climate anomaly 1150 650 cal yr bp was characterised by low storm activity the evidence for high storm activity in the nw mediterranean sea is in agreement with the changes in coastal hydrodynamics observed over the eastern north atlantic and seems to correspond to holocene cooling in the north atlantic periods of low ssts there may have led to a stronger meridional temperature gradient and a southward migration of the westerlies we hypothesise that the increase in storm activity during holocene cold events over the north atlantic and mediterranean regions was probably due to an increase in the thermal gradient that led to an enhanced lower tropospheric baroclinicity over a large central atlantic european domain

a modeling based analysis of the flooding associated with xynthia central bay of biscay storm induced coastal flooding is among the most destructive natural disasters as seen recently in the bay of bengal the gulf of mexico and the philippines this study presents a high resolution hindcast of the flooding associated with xynthia a mid latitude storm that severely hit the central part of the bay of biscay in february 2010 a 2dh fully coupled modeling system is applied to the north east atlantic ocean with a resolution locally reaching a few meters along the coastline of the study area such a fine resolution was required to adequately represent the dikes and the barriers that usually prevent the area from flooding but results in a 1 700 000 element unstructured grid the comparison with the available data reveals that waves and water levels are reproduced with normalized errors of the order of 10 and 5 respectively the extension of the flooding is also well reproduced although with some underestimations along the coastline and overestimation in the inner part of large marshes these limitations are explained by a lack of spatial resolution locally and the absence of several processes in the model such as infragravity waves and wave runup the comparison between our baseline simulation and a simulation where the flooding is disabled by increasing the dike height reveals differences in maximum water levels locally reaching 1 0 m this result is of key importance for coastal management strategies and also questions classical engineering approaches relying on one way nesting

oxygen isotope constraints on the origin and differentiation of the moon we report new high precision laser fluorination three isotope oxygen data for lunar materials terrestrial silicates with a range of 18 o values 0 5 to 22 9 were analyzed to independently determine the slope of the terrestrial fractionation line tfl 0 5259 0 0008 95 confidence level this new tfl determination allows direct comparison of lunar oxygen isotope systematics with those of earth values of 17 o for apollo 12 15 and 17 basalts and luna 24 soil samples average 0 01 and are indistinguishable from the tfl the 18 o values of high and low ti lunar basalts are distinct average whole rock 18 o values for low ti lunar basalts from the apollo 12 5 72 0 06 and apollo 15 landing sites 5 65 0 12 are identical within error and are markedly higher than apollo 17 high ti basalts 5 46 0 11 evolved low ti lapaz mare basalt meteorite 18 o values 5 67 0 05 are in close agreement with more primitive low ti apollo 12 and 15 mare basalts modeling of lunar mare basalt source composition indicates that the high and low ti mare basalt mantle reservoirs were in oxygen isotope equilibrium and that variations in 18 o do not result from fractional crystallization instead these differences are consistent with mineralogically heterogeneous mantle sources for mare basalts and with lunar magma ocean differentiation models that result in a thick feldspathic crust an olivine pyroxene rich mantle and late stage ilmenite rich zones that were convectively mixed into deeper portions of the lunar mantle higher average 18 o wr values of low ti basalts compared to terrestrial mid ocean ridge basalts 0 18 suggest a possible oxygen isotopic difference between the terrestrial and lunar mantles however calculations of the 18 o of lunar mantle olivine in this study are only 0 05 higher than terrestrial mantle olivine these observations may have important implications for understanding the formation of the earth moon system 2006 elsevier b v all rights reserved

the oxygen isotopic record in enstatite meteorites oxygen isotopic compositions were determined for a suite of enstatite chondrites and aubrites in agreement with previous work clayton et al 1984 most samples have o isotopic compositions close to the terrestrial fractionation line tfl and there appear to be no significant differences in o isotopic compositions between individual eh and el chondrites and aubrites five enstatite meteorites have o isotopic compositions that are significantly different from the other samples and 0 2 away from the tfl two of these have petrographic evidence of brecciation and interaction between other meteorite types for the other three similar scenarios are suggested there appears to be a systematic increase in 18o from enstatite chondrites both eh and el of petrologic type 3 to those of type 6 there is also good evidence that the eh meteorites do not fall along a mass fractionation line but along a line slope 0 66 at the present time detailed understanding of the origin of these o isotopic systematics remain elusive but clearly point to a complex accretion history parent body evolution or both

reconstruction of paleostorm events in a coastal lagoon herault south of france article i nfo finding records of past catastrophic storm events is essential to evaluate the long term climatic evolution in a given coastal area this question has been addressed by the study of sediment cores sampled in a small coastal lagoon of the french mediterranean coast pierre blanche lagoon two cores were studied in detail and revealed the presence of three main storm events the sedimentation rates calculated using the cfcs 210 pb model in agreement with 137 cs data are 3 0 4 and 4 2 0 7m m y 1 near the border and in the center of the lagoon respectively this suggests that the 0 6 m deep lagoon could be filled with sediments over the next 150 yr our study shows that storm events can be characterized in sedimentary sequences identified by facies grain size and faunal assemblages lagoonal and marine species comparison of 210 pb 14 c chronology and historical accounts suggest that the three identified

late quaternary sea level changes and crustal movements in eastern england and eastern scotland an assessment of models of coastal evolution abstract the most comprehensive records of late quaternary coastal environmental change in eastern england and eastern scotland are obtained from the intercalated semi terrestrial peats and intertidal silts clays and sands that have accumulated in estuaries and coastal lowlands radiocarbon dated sea level index points from sites in north east england are evaluated with reference to first a conceptual model of coastal sedimentary environments and second a model of pollen assemblages in holocene coastal environments analysis of these new data indicates differential crustal uplift within north east england of ca 0 2 mm yr for the last 4000 to 5000 radiocarbon years this pattern of uplift is consistent with models of holocene crustal deformation in scotland and england the uplift is attributable to the combined effects of ice unloading and water loading

precise determination of the isotopic composition of potassium application to terrestrial rocks and lunar soils we detail a method for the precise and accurate determination of isotopic variations in the 41k39k ratio with a precision of 0 5 2 m purified potassium is chemically extracted from rocks soils minerals or solutions by ion exchange chromatography complete chemical yields 99 8 are achieved in order to avoid laboratory induced isotopic fractionations the purified potassium is converted to a glass by melting with barium borate flux and the resultant bead is mounted for ion probe analysis the sims method utilized by the ion probe produces extremely stable k ion beams with no measurable temporal variability in the isotope ratio the instrumental fractionation is steady at about 4 and is corrected for by measurement of a standard the measurement of gravimetrically prepared isotopic standards indicates that the method is accurate at the stated level of precision and free of egregious errors analysis of terrestrial samples including peridotite basalts granites carbonatite biotite schists and seawater indicate the complete absence of isotopic variations in 41 1k among terrestrial materials at the 0 5 o level application to lunar soils and a regolith breccia confirms previously observed large isotopic fractionation effects garner et al 1975a church et al 1976 some lunar soils e g 14163 are shown to have large sample heterogeneity 7 o while others e g soils and a regolith breccia at several apollo 15 sites station 79 are homogeneous at the level of analytical precision the presence of potassium isotopic effects in bulk soils up to 12 7 in this study with magnitudes comparable to the rayleigh fractionation factor 25 indicates that volatility during micrometeorite impact melting played a large role in lunar regolith formation as much as 15 of the regolith potassium has been lost from the moon through the tenuous lunar atmosphere

reconstruction of prehistoric landfall frequencies of catastrophic hurricanes in northwestern florida from lake sediment records abstract sediment cores from western lake provide a 7000 yr record of coastal environmental changes and catastrophic hurricane landfalls along the gulf coast of the florida panhandle using hurricane opal as a modern analog we infer that overwash sand layers occurring near the center of the lake were caused by catastrophic hurricanes of category 4 or 5 intensity few catastrophic hurricanes struck the western lake area during two quiescent periods 3400 5000 and 0 1000 14 c yr b p the landfall probabilities increased dramatically to ca 0 5 per yr during an hyperactive period from 1000 3400 14 c yr b p especially in the first millennium a d the millennial scale variability in catastrophic hurricane landfalls along the gulf coast is probably controlled by shifts in the position of the jet stream and the bermuda high

silicon in the earth s core the earth and moon have iron isotopic abundances that are slightly heavy compared with mars the asteroid vesta and primitive meteorites the reason for this has been unclear one suggestion is that there was a large scale isotopic equilibration during the giant impact the collision between the early earth and a mars sized body that created the moon but this has seemed unlikely given that most other elements do not show the effect an analysis of 44 meteorite and terrestrial samples now shows that the silicon isotopic compositions of basaltic rocks from the earth and moon are also distinctly heavy the finding is consistent with the isotopic equilibration model and it suggests that silicon was already partitioned into the earth s core as a light element before the moon formed the silicon isotopic compositions of basaltic rocks from the earth and moon are distinctly heavy the similar isotopic composition of the bulk silicate earth and the moon are consistent with large scale isotopic equilibration during the giant impact indicating that si was already a light element in the earth s core before the moon formed small isotopic differences between the silicate minerals in planets may have developed as a result of processes associated with core formation or from evaporative losses during accretion as the planets were built up basalts from the earth and the moon do indeed appear to have iron isotopic compositions that are slightly heavy relative to those from mars vesta and primitive undifferentiated meteorites1 2 3 4 chondrites explanations for these differences have included evaporation during the giant impact that created the moon when a mars sized body collided with the young earth however lithium5 and magnesium6 lighter elements with comparable volatility7 8 9 reveal no such differences rendering evaporation unlikely as an explanation here we show that the silicon isotopic compositions of basaltic rocks from the earth and the moon are also distinctly heavy a likely cause is that silicon is one of the light elements in the earth s core we show that both the direction and magnitude of the silicon isotopic effect are in accord with current theory10 based on the stiffness of bonding in metal and silicate the similar isotopic composition of the bulk silicate earth and the moon is consistent with the recent proposal11 that there was large scale isotopic equilibration during the giant impact we conclude that si was already incorporated as a light element in the earth s core before the moon formed

silicon isotopes in meteorites and planetary core formation the silicon si isotope compositions of 42 meteorite and terrestrial samples have been determined using mc icpms with the aim of resolving the current debate over their compositions and the implications for core formation no systematic 30si differences are resolved between chondrites 30si 0 49 0 15 2 sd and achondrites 30si 0 47 0 11 2 sd although enstatite chondrites are consistently lighter 30si 0 63 0 07 2 sd in comparison to other meteorite groups the data reported here for meteorites and terrestrial samples display an average difference 30sibse meteorite 0 15 0 10 which is consistent within uncertainty with previous studies no effect from sample heterogeneity preparation chemistry or mass spectrometry can be identified as responsible for the reported differences between current datasets the heavier composition of the bulk silicate earth is consistent with previous conclusions that si partitioned into the metal phase during metal silicate equilibration at the time of core formation fixing the temperature of core formation to the peridotite liquidus and using an appropriate metal silicate fractionation factor e 0 89 the 30sibse meteorite value from this study indicates that the earth core contains at least 2 5 and possibly up to 16 8 wt si

middle to late holocene storminess in brittany nw france part ii the chronology of events and climate forcing this study focuses on the recurring climate conditions required for the largest storms occurring in nw france brittany it is based on the analysed records of storm events along western brittany coast see part i in this manuscript part ii storm recurrence is explored along with forcing mechanisms periods of more frequent storm events over the two last centuries are analysed first in order to link these events with possible forcing mechanisms north atlantic oscillation nao and atlantic multidecadal oscillation amo modes triggering the most destructive storms then palaeostorm events are discussed at the holocene scale from 6000 yr bp to present to verify the forcing mechanisms most recorded events appear to be linked with cooling episodes mostly in winter a transition to or from a negative winter nao mode a positive amo mode extreme storms occur immediately prior to the medieval warm period mwp maximum effects are reached prior to the onset of the mwp and during the maunder and dalton solar minima low storm activity occurred during the sporer minimum linked to an acceleration of the atlantic meridional overturning circulation amoc main storm triggers seem to correspond to a positive amo mode with an unstable jetstream configuration driving a negative nao in this study four specific weather configurations were defined to explain each type of recorded storminess the strongest storms correspond to low amo and decennial negative nao modes e g little ice age or high amo in association with dominant low nao modes as during the early middle age and present day period fresh or warm oceans in association with a positive nao mode are stormy but with very low sting storms frequency although in agreement with the orbital forcing and the holocene glacial history increasing storm frequency and intensity is most probably partly biased by continuous sea level rise and resulting erosion

clay minerals and geochemistry record from northwest mediterranean coastal lagoon sequence implications for paleostorm reconstruction abstract the paleostorm history of coastal lagoon environments pierre blanche lagoon central part of the gulf of lions has been established by integrating clay mineralogy and geochemical analysis clay mineralogy combined with bulk major and trace elements concentrations allow for the definition of four different end members the mosson drainage basin the sandy barrier the biogenic and the anthropic components the two main sedimentary sources of the lagoonal system are the mosson drainage basin which has a high concentration of smectite and al 2 o 3 and the sandy barrier characterized by high contents of illite chlorite sio 2 and zr smectite illite chlorite sio 2 al 2 o 3 and zr al 2 o 3 ratios can be used to reconstruct the past storm history of the pierre blanche lagoon our results indicate that the sensitivities of the clay mineralogy and geochemistry proxies are different these sensitivities could be related 1 first to the comparison between different grain size for geochemistry and for clay mineralogy 2 second to the complexity of the mix four end members for the geochemistry and two end members for the clay minerals and 3 third by the storm s ability to transport sediment of different sizes

coastal wetlands reveal a non synchronous island response to sea level change and a palaeostorm record from 5 5 kyr to present here we describe environmental change on lord howe island lhi 31 30 s 159 05 e over the last 5500 cal bp derived from the analysis of the accumulating sediments in four coastal wetlands grain size analyses loss on ignition loi and micrometre resolution x ray fluorescence xrf geochemical data were combined with 10 accelerator mass spectrometry ams 14c dates to determine a chronology of environmental change sedimentary coastal features were initiated on the drowned lhi basalt coastline after 4500 cal bp which was followed by gradual development of wetland environments from 4200 cal bp to present within this period a series of high intensity storm events are recorded perhaps related to low pressure systems including cyclones and east coast low ecl events a lack of synchronicity between the studied sites resulted from their position in the landscape relative to the coast features within the lagoon and greater sediment availability after 2800 cal bp as sediment filled sinks in the

the chronology of late quaternary fluvial activity in part of the milfield basin northeast england the sediment stratigraphy of a 4 m thick intercalated holocene alluvial fill and valley floor peat at a site in the milfield basin northumberland has been dated by a series of eight 14c assays and related to a previously analysed pollen record the sequence extends from the earliest holocene until c 2800 cal bp prior to the onset of peat inception substantial amounts of channel trenching can be demonstrated to have occurred in the milfield basin during the loch lomond stadial there is no measurable early holocene accelerated fluvial activity but a major flooding event occurred at c 7500 cal bp much earlier than recorded elsewhere in the region the explanation for this is not clear however the cessation of mid holocene overbank sedimentation at c 4000 3500 cal bp is tentatively correlated with slope stability associated with woodland regeneration 1998 john wiley sons ltd

reconstruction of paleostorms and paleoenvironment using geochemical proxies archived in the sediments of two coastal lakes in northwest florida abstract late holocene paleoclimate records from coastal regions are important for understanding long term variability of hurricane activity here we present a nearly 4000 year record of severe storm landfalls and environmental changes based on organic geochemical proxies ogps preserved in sediment cores from two coastal lakes in northwest florida our analysis shows that there are significant variations in 13c 15n c n and c n with depth reflecting changes in lake environment which in turn affected the processes delivering water and sediment to the lake as well as biological productivity within the lake isotopic signatures of modern organic materials in the lakes and their surrounding areas show that the major sources of sedimentary organic matters in the lakes are aquatic and terrestrial c3 vegetation c4 grasses do not contribute significantly to the sedimentary organic matters in the lake although they can be found in the mostly forested watershed thus the positive c and n isotopic shifts concurrent with negative shifts in c n ratios most likely indicate shifts to a marine like environment in coastal lakes following the influx of marine water and nutrients and marine biota associated with major storm events some of these isotopic shifts observed in the sediment cores correspond to visible sand layers presumably representing overwash deposits associated with severe storm events radiocarbon dating of bulk sediment organic matters wood fragments and shells indicates that the sediment in these cores was deposited over the last 3000 4000 years based on our age model and ogp interpretation eastern lake data suggest that the recurrence interval of severe storms i e large enough to cause seawater flooding of the lakes is approximately 84 years over the last 2900 years whereas western lake data suggest an average recurrence interval of 86 years in the past 3900 years

tungsten isotopic evolution during late stage accretion constraints on earth moon equilibration abstract we couple the results of n body simulations of late stage accretion o brien et al 2006 to a hafnium tungsten hf w isotopic evolution code to investigate the evolution of planetary bodies in the inner solar system simulations can simultaneously produce planets having earth and mars like masses and hf w systematics by assuming that the tungsten partition coefficient decreases with increasing semi major axis e g due to increasing oxidation simulations assuming that jupiter and saturn occupy circular orbits are more successful at reproducing the hf w systematics than those assuming present day jupiter and saturn orbits to generate earth like tungsten anomalies 30 80 of each impactor core is required to re equilibrate with the target mantle some model outcomes yield a target and final impactor having similar earth and moon like tungsten anomalies however in no case can the inferred lunar hf w ratio be simultaneously matched this result suggests that the moon isotopically equilibrated with the earth s mantle in the aftermath of the giant impact cf pahlevan and stevenson 2007 alternatively either the dynamical models which show the moon being derived primarily from the impactor mantle or the accretion timescales obtained by the n body simulations are incorrect

silicon isotope evidence against an enstatite chondrite earth the compositions of earth materials are strikingly similar to those of enstatite chondrite meteorites in many isotope systems although this suggests that earth largely accreted from enstatite chondrites definitive proof of this model has been lacking by comparing the silicon si isotope signatures of several extraterrestrial materials with terrestrial samples we show that they cannot be explained by core formation scenarios involving a bulk earth of enstatite chondrite composition si isotope similarities between the bulk silicate earth and the moon preclude the existence of a hidden reservoir in the lower mantle a necessary condition of the enstatite chondrite model and require an equilibrium process after the moon forming impact a three end member chondritic mixing model for earth reconciles the si isotope similarities between enstatite chondrites and earth

holocene coastal change and geoarchaeology at howick northumberland uk the recent discovery of one of the earliest mesolithic occupation sites in northern britain at howick on the northumberland coast in association with multiperiod archaeological evidence nearby highlights the importance of uk coastal settings as focii of human occupation through the holocene environmental evidence from a nearby river valley 8 15 m of sediment ranging in age from about 12 000 cal bp to the present records local and regional environmental change twenty four radiocarbon dates based on plant macrofossils provide a strong chronological framework calcareous microfossil assemblages foraminifera ostracods have been recovered from the fine grained sediments recording a change from marine through to brackish and eventually freshwater conditions between about 8200 and 6500 cal bp a preliminary pollen study of the core has permitted a reconstruction of the regional vegetation as it responded to climatic amelioration and human influence upon the landscape radiocarbon dating and sedimentological evidence indicates a major hiatus between approximately 11 000 and 8000 years bp including the period of mesolithic occupation represented by a 30 cm layer of coarse sands and sandstone pebbles probably the result of a significant high energy event dated to about 8300 cal bp although not a typical tsunami deposit the age and context suggests that this may be associated with the storegga slide event already well documented along the eastern coast of scotland the sedimentary and biological remains at howick record environmental change over much of the holocene and are compared with other environmental change records from the region to provide an environmental framework for the archaeology of this coastline

the use of ostracods from marginal marine brackish waters as bioindicators of modern and quaternary environmental change abstract ostracoda microscopic aquatic crustacea from brackish waters have a great potential for ecological monitoring and palaeoenvironmental analyses in highly variable environments this has been proven in many articles during recent decades but their potential has yet to be fully developed or utilised the analysis of ostracod assemblage composition species distributions eco phenotypic variability and the analysis of stable isotopes and trace elements in ostracod shells provide valuable information on present and past water salinity temperature and chemistry hydrodynamic conditions substrate characteristics climate sea level variations oxygen and nutrient availability this article provides an overview on the application of ostracods from brackish waters for palaeoenvironmental reconstruction in the quaternary and for environmental studies in present day environments

contrasting sediment records of marine submersion events related to wave exposure southwest france abstract sediment records of two contrasting backshore coastal marshes extremely vulnerable to recent and historical marine flooding events located on the sw coast of france have been investigated using a multiproxy approach the studied marshes are 30 km apart and have been flooded by similar storm events 7 marine floods in the last 250 years one is located in a wave exposed coast but isolated from the sea by a sediment barrier whereas the other is located in a sheltered estuarine environment and isolated from the sea by a dike one core was collected in each marsh and information on grain size foraminifera shell contents and stable carbon isotopes was obtained along with an age model using 210 pb 137 cs and 14 c core data combined with historical maps give evidence of a typical estuarine backfilling part of the holocene regressive parasequence including an intertidal mudflat at the base and a backshore environment at the top despite the absence of grain size anomalies marine flood related sedimentation in the backshore area of both marshes is identified by a mixture of marine and terrestrial features including marine fauna vegetation debris and variation in the 13 c signature of the organic fraction very low sedimentation rates between flood events and or bioturbation prevents the identification of individual episodic marine floods in the sediment succession comparison of the two sedimentary successions shows that the foraminifera deposited by marine submersions are of two different types foraminifera are monospecific and originate from the upper tidal mudflat in the sheltered marsh whereas in the backshore marsh located in a wave exposed environment they show higher diversity and originate from both shallow and deeper water marine environments this study shows that wave exposure can control the faunal content of marine flood sediment records in coastal marshes

lipid stratigraphy of a flandrian peat bed northumberland uk comparison with the pollen record a flandrian peat bed near low hauxley northumberland uk was studied both optically and geochemically to compare the pollen and lipid records of changing plant input during its accumulation a pr

high resolution analysis of a tsunami deposit case study from the 1755 lisbon tsunami in southwestern spain abstract a multi proxy approach using trench sediment analysis on the southwestern coast of spain los lances bay andalusia provides a high resolution record of the 1755 lisbon tsunami and offers new means to interpret tsunami deposits a combination of sedimentological grain size sorting ams micromorphological x ray tomography and radiography thin sections and geochemical analyses x ray microfluorescence icp aes combines to provide a comprehensive reconstruction of the different phases of tsunami deposition and flow dynamics vertical variations in sediment texture fabric and composition of the 1755 tsunami deposits in los lances are then discussed with reference to existing literature on diagnostic criteria commonly used for identifying and interpreting tsunami deposits finally possible leads for future investigation are proposed

problems encountered with the 14c dating of peat abstract pairs of neighbouring short columns of peat from two sites in northern england were divided into contiguous 1 cm thick slices that were sub sampled for pollen and plant macro fossil analysis for each slice the remaining peat was then split into humic acid humin and fulvic acid fractions and radiocarbon dated this research demonstrates that significant variations can occur in the radiocarbon content of discrete chemically defined fractions of peat a total of 127 radiocarbon dates was obtained the results from the four columns of peat are highly variable and mutually inconsistent the fulvic acid fraction although normally younger than the corresponding humic acid and humin fractions has very little effect on a combined date in these samples however it is removed from all samples prior to dating in order to remove any carbonates which could contaminate samples the variations in the ages obtained for the humic acid and corresponding humin fractions range from the humin fraction being 630 years older than the humic acid srr 4029 to the humic acid being 1210 years older than the humin fraction srr 4007 even when a two sigma confidence is allowed no correlation was apparent between pollen concentration 13 c enrichment degree of humification and the conventional radiocarbon ages

new w isotope evidence for rapid terrestrial accretion and very early core formation the short lived hf 182 w 182 isotope system is an ideal clock to trace core formation and accretion processes of planets planetary accretion and metal silicate fractionation chronologies are calculated relative to the chondritic hf 182 w 182 isotope evolution here we report new high precision w isotope data for the carbonaceous chondrite allende that are much less radiogenic than previously reported and are in good agreement with published internal hf w chronometry of enstatite chondrites if the w isotope composition of terrestrial rocks representing the bulk silicate earth is homogeneous and 2 24 epsilon 182w units more radiogenic than that of the bulk earth metal silicate differentiation of the earth occurred very early the new w isotope data constrain the mean time of terrestrial core formation to 34 million years after the start of solar system accretion early terrestrial core formation implies rapid terrestrial accretion thus permitting formation of the moon by giant impact while hf 182 was still alive this could explain why lunar w isotopes are more radiogenic than the terrestrial value copyright c 2002 elsevier science ltd

use of anisotropy of magnetic susceptibility ams in the study of tsunami deposits application to the 2004 deposits on the eastern coast of banda aceh north sumatra indonesia abstract we studied emplacement dynamics of the december 26 2004 tsunami deposits in artificial shallow ponds and in shallow lagoons along the northern coast of sumatra in banda aceh area successive tsunami waves inundated topographic lows which acted as sediment traps and favored preservation of deposits individual waves led to the deposition of fining upwards sedimentary sequences this multiple normal grading deposit with a thickness ranging from 2 to 80 cm constitutes a site of major interest for the study of the deposits emplaced by a tsunami wave train the main interest lies in the characteristics of the deposits that can be correlated to the behavior of the waves attested by numerous testimonies in this setting we aimed at testing the applicability of the ams anisotropy of magnetic susceptibility technique as a proxy of unconsolidated sediment fabric the combination of this proxy and traditional sedimentary analysis helped reconstructing the hydrodynamic conditions particularly the flow direction prevailing during sedimentation we applied the ams technique on eight sections stretching inland from 1 5 km to 2 2 km from the pre tsunami coastline grain size and ams data from these deposits provide similar and partially complementary information traction dominates in the basal parts of the deposits and occurs mainly for the basal layers of the sequences whereas settling dominates for the upper layers of these sequences the vertical evolution of the ams parameters within the deposits is related to the arrival of the successive waves with variations in the traction and decantation processes during deposition variations of current strength during sedimentation are related to the wave s momentum and to the progressive infill of topographic depressions the vertical change of the fifth coarsest percentile vs the median grain sizes of the deposits suggests strong variations of the energy of the currents and confirms the evolution of the ams parameters in the present study the fabric of the deposits which developed exclusively during the uprush phase of the cycle also allows the reconstruction of flood directions that are both normal and parallel to the shoreline with variations related to flow dynamics mean grain size and local topographic control due to the absence of backwash in between the waves and low velocity of the final backwash information about the sedimentation conditions of the tsunami deposits appears to be better preserved in topographic depressions in areas located remote from the seashore the ams proxy appears to be a promising tool for further studies of recent and paleo tsunami deposits

silicon isotopes in lunar rocks implications for the moon s formation and the early history of the earth silicon isotopic data from a range of lunar samples are presented to assess the degree of heterogeneity of the lunar mantle and its similarity to bulk silicate earth bse multi collector inductively coupled plasma mass spectrometry mc icpms was used to analyse 24 samples including both high and low ti basalts as well as highland anorthosites and picritic glasses covering all the apollo sample return missions no systematic 30si differences are found between any of the bulk sample lithologies 2 sd 30silow ti basalt 0 29 0 06 30sihigh ti basalt 0 32 0 09 30silunar glass 0 29 0 05 and 30sihighland rocks 0 27 0 10 the average of the lunar samples is 30si 0 29 0 08 2 sd which is identical to the composition of bse 30si 0 29 0 08 2 sd from savage et al 2010 the bse si isotope composition is thought to be the result of si partitioning between metal and silicate and consequent isotopic fractionation during core formation the moon forming impactor would not be expected to share that composition because it is thought to have been relatively small 0 1 earth masses like mars and formed under relatively low temperatures and pressures that are insufficient for si to partition into the core therefore the identical lunar and bse si isotope data show that si isotopes like those of oxygen must have homogenised in the aftermath of the moon forming impact if smooth particle hydrodynamic simulations of the giant impact are correct in showing that most lunar material should have originated from the impactor rather than the earth the data presented here are in agreement with other isotope systems and experimental studies that indicate that the majority of core formation happened early and before the giant impact it has been predicted pahlevan et al 2011 that the moon and the bse should show a 0 14 offset in 30si for the moon to have an fe fe mg ratio twice that of bse the current resolution and sample population size of the si data for the moon and earth would allow such an offset to be detected the fact that is it not observed can put constraints on the element ratios and lunar budgets as modelled by pahlevan et al 2011 in particular it constrains the fe fe mg ratio of the moon to be only 1 1 3 bse

evidence for oxidizing conditions in the solar nebula from mo and w depletions in refractory inclusions in carbonaceous chondrites abstract depletions of mo and w relative to other refractory metals of similar volatility re os ir ru pt are common in a suite of 16 ca al rich inclusions cais from 5 carbonaceous chondrites twelve of the 16 cais from allende grosnaja leoville and ornans show mo depletions six of these 12 inclusions also show w depletions the one cai analyzed from the essebi chondrite shows no depletions the mo and w depletions have a very characteristic pattern with mo always more depleted than w the same mo and w depletion pattern occurs in calculated refractory metal alloy compositions formed at oxygen fugacities 10 3 to 10 4 times greater than the canonical solar nebula oxygen fugacity we conclude that mo and w depletions are common in cais from carbonaceous chondrites and that the depletions result from high temperature oxidation the oxidation may have occurred during the evaporation of primitive dust into cais but is also consistent with condensation at high oxygen fugacities no potential alternative processes appear to be capable of producing the observed mo and w depletion patterns

a hit and run giant impact scenario abstract the formation of the moon from the debris of a slow and grazing giant impact of a mars sized impactor on the proto earth cameron and ward 1976 lunar planet sci conf canup and asphaug 2001 nature 412 708 is widely accepted today we present an alternative scenario with a hit and run collision asphaug 2010 chem erde 70 199 with a fractionally increased impact velocity and a steeper impact angle

evaporation of olivine low pressure phase relations of the olivine system and its implication for the origin of chondritic components in the solar nebula low pressure phase relations and vapor pressures of forsterite and fayalite were studied with the knudsen method in the temperature range of 1400 1860 c for forsterite and 1100 1160 c for fayalite the triple points are 5 2 10 5 bar 1890 c and 6 3 10 8 bar 1217 c for forsterite and fayalite respectively the enthalpy and entropy of evaporation of forsterite are hv 543 33 kj mol and sv 169 21 j mol k and those for fayalite are 502 9 kj mol and 199 6 j mol k respectively by assuming that gas and olivine are ideal solutions vaporous and solidus curves of the olivine solid solution system in the pressure range from 10 10 to 10 3 bar were calculated from the thermochemical data at pressures above the triple point of forsterite the phase diagram is the same as that at 1 bar because the vapor field is at higher temperatures than those of liquid bearing fields at pressures between the triple points of forsterite and fayalite liquid bearing stability fields appear below the gas solid stability field in the fe rich portion of the system the compositional range of liquid bearing fields expand with increasing pressure at 10 4 bar the liquid bearing fields cover most of the olivine system xmg 0 9 liquid is absent at pressures below the triple point of fayalite regardless of the composition large mgfe fractionation between gas and solid is more extensive compared to the solid and liquid relationship when heated in equilibrium olivine melts before evaporation in the pressure range of 10 7 10 3 bar in a solar nebula with total pressure of 10 3 bar olivine melts when the nebula is enriched in dust by more than an order of magnitude over the solar nebular value and when the mg si fe h ratio increased the origin of type ia and ii chondrules and matrix olivine in ordinary and carbonaceous chondrites can be explained in terms of the pressure of olivine gas type ia chondrules were formed in the gas solid phase field where volatiles feo na2o and others were lost during heating events responsible for chondrule formation the residual materials became enriched in refractory elements type ii chondrules were formed in the temperature range of the liquid solid phase field under these conditions the original compositions were retained after heating of chondrule formation provided that type ia and ii chondrules were formed at a similar temperature type ia chondrules were formed at an olivine pressure one order of magnitude lower than that of type ii chondrules in this model matrix olivine is a condensate from gas which formed by partial evaporation of chondritic material during type ia chondrule formation

the future of tsunami research following the 2011 tohoku oki event abstract in this paper we summarize the regional setting our previous understanding of historical and pre historical tsunamis on the pacific coast of tohoku japan prior to the 2011 tohoku oki tsunami and our current understanding of the sedimentological geochemical and paleontological features of the onshore and offshore deposits of the event post tsunami surveys revealed many new insights such as 1 the maximum extent of the sand deposit is sometimes only 60 of the inundation distance 2 the inundation limit can be estimated by geochemical analysis even a few months after the event 3 a minor amount of marine sediment was transported inland by the tsunami on the sendai and adjacent plains with the major sediment sources being from beach and dune erosion or vented sediments from liquefaction although nearshore and offshore surveys revealed that there was a significant amount of sediment transport on the seafloor 4 coarse gravel deposits 1 m in thickness were usually thicker than the sand ones 30 cm in thickness and 5 beach erosion was minimal in some places while severe in others another important aspect of this event is that it was a large infrequent tsunami that took place where possible predecessors e g ad869 j gan were already known to have occurred based on historical and geological evidence the ad869 j gan tsunami deposits are noticeably similar to the 2011 tohoku oki sands therefore suggesting that the j gan and its source mechanism may have been larger than previously thought while we have learned many lessons from the 2011 tohoku oki event more research is needed to provide reliable tsunami risk assessments around the world

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

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