holocene evolution of phra thong s beach ridge plain thailand chronology processes and driving factors abstract beach ridge plains are a common morphological element of coastal areas all over the world while morphological depressions of beach ridge plains swales may function as archives for deposits of extreme wave events the ridges are not only used as an indicator for coastal evolution but also to reconstruct the processes that are responsible for their formation in this study the morphological sedimentary and chronological structure of the beach ridge plain on phra thong island was used as an archive for the temporally and spatially complex pattern of shoreline changes during the holocene the presence of three spatio temporal ridge plain units separated by episodes of shoreline erosion and characterised by varying directions and rates of shoreline progradation reveals six distinct phases of island evolution within the last 6000 years unit i was deposited during phase 1 5500 4000 years ago with high progradation rates of 2 1 2 5 m year subsequent to a short episode of erosion during phase 2 4000 3800 years ago fast shoreline progradation at a rate of 2 7 m year unit iia occurred once again in phase 3 3800 3300 years ago after 3300 years ago the sedimentation rate decreased to less than 1 m year resulting in the formation of unit iib during phase 4 3300 1500 years ago in phase 5 between 1500 and 800 years ago ridge plain formation was once more interrupted by significant shoreline erosion finally over most of the last 800 years during phase 6 slow shoreline progradation led to the formation of unit iii this evolution is best explained by the interaction of long term sea level change wave climate episodic events tsunamis and storms and local sediment supply however the linkage of successive ridge and swale formation changing progradation rates and switch over between phases of erosion and deposition with its trigger mechanisms remains speculative since i the processes involved vary locally and are poorly understood for phra thong island and ii even our comparably large dataset cannot reconstruct the complex spatial and temporal pattern of shoreline evolution without significant uncertainties this implies that interpretations of ridge plains based on small datasets might be too generalised to capture the real complexity of the system and as a consequence might lead to incorrect conclusions about palaeoenvironmental conditions

al rich objects in ordinary chondrites related origin of carbonaceous and ordinary chondrites and their constituents ca al rich inclusions cais common constituents of carbonaceous chondrites have been studied extensively because they contain refractory high temperature minerals suggesting that they formed at high temperatures during the early history of the solar system few cais have previously been discovered in ordinary chondrites here we describe 169 al rich objects arbitrarily defined as having 10 wt al2o3 from 24 types 3 and 4 ordinary chondrites five regolith breccias containing unequilibrated material the unique meteorite kakangari and a few types 5 and 6 ordinary chondrites based on shape and texture we divide al rich objects into chondrules round with igneous textures irregularly shaped inclusions similar to type f and spinel rich complex cais and fragments probably fragments of al rich chondrules and inclusions for descriptive purposes we further subdivide al rich chondrules into compositional subgroups although they are entirely transitional conclusions 1 a al rich chondrules and irregularly shaped inclusions and fragments are wide spread albeit rare constituents of ordinary chondrites and are similar to cais except the coarse grained ones in carbonaceous chondrites thus providing strong support for a related origin of ordinary and carbonaceous chondrites and their constituents 2 b al rich chondrules formed as independent freely floating molten droplets and cooled rather rapidly 3 c al rich chondrules like the common mg fe rich chondrules formed by melting of millimeter to submillimeter sized dust balls in the case of al rich chondrules the dust balls consisted largely of mixtures of variable amounts of at least two solid precursor materials one refractory rich and the other volatile rich phases which we interpret as unmelted relicts in some of these objects support this model 4 d the wide ranges in bulk compositions of al rich chondrules from refractory rich to volatile rich ones yet complete transition between them and the existence of chondrules transitional in composition between the al rich and common mg fe rich chondrules of ordinary chondrites suggest that all chondrules formed by related processes differences in bulk composition result from mixing of different proportions of refractory volatile and mg fe rich and other solid precursor materials into dust balls which were then melted 5 e most irregularly shaped inclusions show no indication of a once molten origin secondary alteration has probably changed the original mineral assemblage mainly volatile rich materials entered the refractory objects as a gas reacted with the constituents and produced secondary phases rims probably formed both by decomposition and reaction with solar gas as well as by accretion 6 f coarse grained inclusions as found in allende were not observed in ordinary chondrites

evidence for a transgressive barrier within a regressive strandplain system implications for complex coastal response to environmental change clastic depositional strandplain systems have the potential to record changes in the primary drivers of coastal evolution climate sea level and the frequency of major meteorological and oceanographic events this study seeks to use one such record from a southern brazilian strandplain to highlight the potentially complex nature of coastal sedimentological response to small changes in these drivers following a 2 to 4 m highstand at ca 5 8 ka in southern brazil falling sea level reworked shelf sediment onshore forcing coastal progradation smoothing the irregular coastline and forming the 5 km wide pinheira strandplain composed of ca 500 successive beach and dune ridges sediment cores grab samples and 11 km of ground penetrating radar profiles reveal that the strandplain sequence is composed of well sorted fine to very fine quartz sand since the mid holocene highstand the shoreline prograded at a rate of ca 1 to 2 m yr 1 through the deposition of a 4 to 6 m thick shoreface unit a 1 to 3 m thick foreshore unit containing ubiquitous ridge and runnel facies and an uppermost beach and foredune unit however the discovery of a linear 100 m wide barrier ridge with associated washover units a 3 to 4 m deep lagoon and 250 m wide tidal inlet within the strandplain sequence reveals a period of shoreline transgression at 3 3 to 2 8 ka during the otherwise regressive developmental history of the plain the protected nature of pinheira largely buffered it from changes in precipitation patterns wave energy and fluvial sediment supply during the time of its formation however multiple lines of evidence indicate that a change in the rate of relative sea level fall probably due to either steric or ice volume effects may have affected this coastline thus whereas these other potential drivers cannot be fully discounted this study provides insights into the complexity of decadal scale to millennial scale coastal response to likely variability in sea level change rates

intra shoreface erosion in response to rapid sea level fall depositional record of a tectonically uplifted strand plain pacific coast of japan this study documents lowering of the surf zone i e the upper shoreface leading to intra shoreface erosion following two rapid relative sea level falls along a tectonically uplifted coast during the holocene and the characteristics of the resultant prograding shoreface deposits these findings are based on high resolution analysis and radiocarbon dating of three new drill cores obtained from the kujukuri strand plain pacific coast of eastern japan combined with previously published borehole data and information on modern shoreline profile adjustments a shallowing upward sandy succession composed of lower and upper shoreface facies foreshore and backshore facies was recognized in the drill cores two rapid falls in relative sea level at 2ae 3t o 2ae6 and 1ae 8t o 2ae0 ka are recorded by downstepping of the base of the foreshore facies and farther seawards by the lowering of an erosional boundary between the upper and lower shoreface facies superimposed bed profiles of an adjacent modern beach define an envelope the base of which reflects shore normal migration of longshore bars and troughs the base of the envelope represents an erosional surface that divides the surface mobile layer above from preserved deposits beneath the surface is concave upwards and steeper than the mean beach profile and exhibits a flat platform approximately at the lower limit of the upper shoreface equating to the storm surf zone the seaward transition of this surface rather than the mean equilibrium profile controls the metre scale to decimetre scale internal structure of the kujukuri shoreface deposits depositional models for sea level fall based on an exponential equilibrium profile do not adequately account for the presence and migration of longshore bars and troughs

chondrules from chainpur ll 3 reduced parent rocks and vapor fractionation abstract nineteen chondrules from the chainpur ll 3 chondrite were analyzed for their bulk lithophile element contents and mineral chemistries chondrule compositions are highly fractionated the following compositional groups can be distinguished 1 refractory depleted in na and k 2 k depleted k ci na ci 3 approximately chondritic na k ci na ci and 4 k enriched k ci na ci the most refractory chondrules are depleted in k 0 11 ci abundances normalized to sc na 0 26 mn 0 52 and cr 0 71 therefore we conclude that the refractory group was mainly produced by vapor fractionation during the chondrule forming event the majority of chondrules in enriched in na 1 37 1 40 ci but fractionated in k which ranges from 0 4 ci k depleted to 2 84 ci k enriched for the fractionation of k from na we suggest a separation mechanism via alkali sulfides uncorrelated fractionations of ca mn cr eu yb sm give supporting evidence for such a mechanism these findings imply that the pre chainpur matter went through highly reducing conditions high h2 o2 and s2 o2 ratios before it was sampled by the chondrule forming process most chondrules of our suite have similar fa contents in olivine 11 21 and are enriched in volatile elements from this we conclude that these chondrules were formed under oxidizing conditions in a relatively dense atmosphere with high partial pressures of volatile elements alkalis halogens a proto planetary atmosphere could have provided these conditions the fractionation process proposed should also be applicable to fractionations on a large scale like the na k and mg si fractionations among chondrites

size frequency distributions of chondrules and chondrule fragments in ll3 chondrites implications for parent body fragmentation of chondrules we measured the sizes and textural types of 719 intact chondrules and 1322 chondrule fragments in thin sections of semarkona ll3 0 bishunpur ll3 1 krymka ll3 1 piancaldoli ll3 4 and lewis cliff 88175 ll3 8 the mean apparent diameter of chondrules in these ll3 chondrites is 0 80 units or 570 um much smaller than the previous rough estimate of 900 m chondrule fragments in the five ll3 chondrites have a mean apparent cross section of 1 60 phi units or 330 m the smallest fragments are isolated olivine and pyroxene grains these are probably phenocrysts liberated from disrupted porphyritic chondrules all five ll3 chondrites have fragment chondrule number ratios exceeding unity suggesting that substantial numbers of the chondrules in these rocks were shattered most fragmentation probably occurred on the parent asteroid porphyritic chondrules porphyritic olivine porphyritic pyroxene porphyritic olivine pyroxene are more readily broken than droplet chondrules barred olivine radial pyroxene cryptocrystalline the porphyritic fragment chondrule number ratio 2 0 appreciably exceeds that of droplet textured objects 0 9 intact droplet chondrules have a larger mean size than intact porphyritic chondrules implying that large porphyritic chondrules are fragmented preferentially this is consistent with the relatively low percentage of porphyritic chondrules within the set of the largest chondrules 57 compared to that within the set of the smallest chondrules 81 differences in mean size among chondrule textural types may be due mainly to parent body chondrule fragmentation events and not to chondrule formation processes in the solar nebula

chondrules in the sharps h3 chondrite evidence for intergroup compositional differences among ordinary chondrite chondrules abstract bulk compositions of 19 chondrules and one matrix rich sample from h3 4 sharps were determined by instrumental neutron activation analysis samples were characterized petrographically and mineral compositions were determined by electron microprobe analysis there is constancy among ordinary chondrite oc groups in the compositional interrelationships of different chondrule types e g in h3 as well as l3 and ll3 chondrites porphyritic chondrules are more refractory than nonporphyritic chondrules precursor components of h3 chondrules are closely related to those of ll3 chondrules the mean ir ni ir co and ir au ratios of h3 chondrules differ from the corresponding ratios of ll3 chondrules at the 99 90 and 79 confidence levels respectively the ratios in h3 chondrules exceed those in ll3 chondrules by amounts similar to those by which h whole rocks exceed ll whole rocks these data suggest that there are primary systematic differences in bulk composition between h and ll chondrules these differences support the inference that chondrule formation occurred after major nebular fractionation events had established the observed bulk compositional differences among oc groups

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

refractory precursor components of semarkona chondrules and the fractionation of refractory elements among chondrites abstract chondrules from the semarkona ll3 0 chondrite show refractory and common lithophile fractionation trends similar to those observed among the chondrite groups it appears that chondrules are mixtures of a small number of pre existing solid components and we infer that chondrule precursor materials were related to the nebular components involved in the lithophile element fractionations recognized in ordinary chondrites compositional trends among the chondrules can be used to deduce the compositions of these components we use instrumental neutron activation analysis to measure many 20 of the lithophile elements in 30 chondrules the amounts of oxidized iron were calculated from other compositional parameters concentrations of si were estimated using mass balance considerations the data were corrected for the diluting effects of non lithophile constituents plots of lithophile elements versus a reference refractory element such as al show that there were two major chondrule silicate precursor components a refractory olivine rich feo free one and a non refractory sio 2 feo rich one the refractory component probably forms from olivine enriched condensates formed above the condensation temperature of enstatite the non refractory component must have formed from fine grained materials that were able to equilibrate down to lower nebular temperatures chondrite matrix may have had an origin similar to that of the non refractory material and constitutes a third lithophile bearing component that took part in chondrite fractionation processes the low abundance of refractories and mg in ordinary and enstatite chondrites was produced by the loss of materials having a higher refractory element mg ratio than that in the refractory component of chondrules

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

insights into barrier island stability derived from transgressive regressive state changes of parramore island virginia abstract barrier islands and their associated backbarrier ecosystems front much of the u s atlantic and gulf coasts yet threshold conditions associated with their relative stability i e state changes between progradation erosion and landward migration in the face of sea level rise remain poorly understood the barrier islands along virginia s eastern shore are among the largest undeveloped barrier systems in the u s providing an ideal natural laboratory to explore the sensitivity of barrier islands to environmental change details about the developmental history of parramore island one of the longest 12 km and widest 1 0 1 9 km of these islands provide insight into the timescales and processes of barrier island formation and evolution along this mixed energy coast synthesis of new stratigraphic vibra auger and direct push cores geospatial historical maps aerial imagery t sheets lidar and chronologic optically stimulated luminescence radiocarbon analyses reveals that parramore has alternated between periods of landward migration erosion and seaward progradation during the past several thousand years new chronology from backbarrier and barrier island facies reveals that parramore island has existed in some form for nearly 5000 years following a period of rapid overwash driven retrogradation and coinciding with a period of slow relative sea level rise 1 mm yr parramore stabilized 1000 years ago in partial response to pinning by and sediment delivery from erosion of a pleistocene aged antecedent high following pinning parramore built seaward through development of successive progradational beach and dune ridges morphological and historical evidence suggests that these processes were interrupted by inlet formation possibly associated with an interval of enhanced storminess at least three times during this period following inlet closure in the early 1800s island progradation was rapid with parramore island reaching its maximum width ca 150 years ago it has since switched states again undergoing accelerating erosion 12 m yr since 1980 the relative youth of parramore island is in contrast to many east coast barrier islands which generally reached their present positions about 3500 2000 years ago moreover these results demonstrate that the apparent robustness and stability of parramore are ephemeral features of an island that has undergone multiple state changes within the last 1000 years finally they refine current knowledge of the roles of antecedent topography sediment delivery rates storms and sea level rise in barrier island stability and resilience to future climate change

the complex prograded cassino barrier in southern brazil geological and morphological evolution and records of climatic oceanographic and sea level changes in the last 7 6 ka abstract this paper presents the geological and morphological evolution of the prograded cassino barrier during the middle and late holocene a special focus is given on the presentation and discussion of records of environmental changes that occurred during barrier progradation the results demonstrated that variable rates of progradation were produced by environmental changes that affected the coastal sediment budget such as changes in the wave climate the total progradation of 18 km recorded for the cassino barrier is probably the highest extension of progradation registered for a ridge plain associated with a coastal barrier sea level changes during barrier progradation were accessed by the high difference between the degree of compaction of the foredune and backshore foreshore deposits detected by the drilling system applied in this study and were confirmed by the limit of those deposits which were also revealed by gpr records during most of the time of barrier progradation an overall sea level fall of approximately 2 1 m occurred six sets of relict foredune ridges were identified and the limits between them were well marked by ridge truncations and the formation of transgressive dune sheets tds optically stimulated luminescence ages show that the tds were formed under the driest climate conditions with age periods very close to 3 8 3 5 1 9 1 5 0 22 and 0 09 ka ago interspersed with ages of known wetter conditions in southern brazil the modern phases of tds formation with ages varying from 0 25 to 0 22 ka ago were coincident with the time period of the younger pulse of the little ice age lia which was characterized by arid and cold conditions in southern south america a comparison with prograded barriers located 350 to 600 km to the north suggests the existence of teleconnections with phases of tds and parabolic dunes that formed with a time interval of approximately 405 to 583 years

evidence of terrestrial organic matter deposition across the early toarcian recorded in the northern lusitanian basin portugal abstract the pliensbachian toarcian lower jurassic in the lusitanian basin portugal is particularly well exposed through marl limestone alternations very rich in nektonic and benthonic macrofauna in the general context of toarcian oceanic anoxic event t oae the lower toarcian polymorphum and levisoni ammonite zones marks important sedimentological changes in the marine paleoenvironment to better understand the paleoenvironmental changes that occurred during the latest pliensbachian early toarcian a high resolution study of organic matter was undertaken in the alcabideque section in the northern sector of the basin based on the analysis of 14 samples from a section 20 m thick this study involved organic geochemistry total organic carbon toc sulfur and biomarkers and palynofacies the results confirm that sediments are particularly poor in organic matter with the highest toc values reaching 0 41 wt around the top of polymorphum zone the palynofacies analysis provides evidence that the organic matter largely consists of particles belonging to phytoclasts and palynomorphs groups the phytoclasts present were generally degraded and oxidized with significant representation in the emaciatum and polymorphum zones the palynomorphs were mainly composed by sporomorphs with a sporadic increase in marine palynomorphs mainly dinocysts at the top of the emaciatum and polymorphum zones continental organic matter was predominant at the base of levisoni zone t oae through the deposition of brownish marls chocolate marls which was confirmed by the occurrence of tetrads and polyads pollen grain agglomerates and by biomarkers with the major presence of long chain n alkanes n alkane c17 c20 tricyclic terpane c24 tetracyclic terpane and c29 regular sterane the gammacerane index shows a peak at the top of polymorphum zone clearly associated with the increase of marine palynomorphs and the maximum marine influence in the series

relict and other anomalous grains in chondrules implications for chondrule formation we have identified relict olivine and pyroxene grains in chondrules from ordinary and carbonaceous chondrites that probably did not crystallize in situ some of these olivines are clear but others contain fine grained fe ni dusty olivines and resemble previously described occurrences in ordinary chondrites there are also chondrules in which all olivine is dusty we conclude 1 not all relict olivines are dusty 2 not all dusty olivines crystallized outside the chondrule in which they occur and 3 some dusty olivines were produced during chondrule formation by a reduction process that affected the whole chondrule the occurrence of dusty olivines and relict pyroxenes and olivines in chondrules from carbonaceous as well as ordinary chondrites supports the argument that chondrules from all chondrites had similar origins and histories we propose that chondrules and mineral fragments were transported across f o2 gradients in the solar nebula while they were hot or were reheated in an environment different from the one in which they formed partially molten chondrules sometimes incorporated mineral grains or chondrules with different redox states producing compound chondrules and chondrules containing anomalous grains dusty olivines may also have formed when hot chondrules were transported to regions of lower oxygen fugacity

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

gpr in sediments advice on data collection basic processing and interpretation a good practice guide within sedimentological studies ground penetrating radar gpr is being used with increasing frequency because it yields images of the shallow subsurface that cannot be achieved by any other non destructive method the purpose of this paper is to provide an introduction to the collection processing and interpretation of gpr data so that future sedimentary studies can be improved with gpr equipment now being lightweight robust and portable proper data collection and survey design methods need to be followed in order to acquire high resolution subsurface digital data various factors are discussed including reflection profiling velocity soundings test surveys topography logistics data quality and extreme environments basic data processing and visualization are then reviewed followed by a discussion on gpr interpretation strategies including a background to radar stratigraphy for the sedimentary geologist or geomorphologist gpr offers unique data of the shallow subsurface including stratigraphy geometry architecture and structure

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

holocene sea level change on the southeast coast of australia a review a revised holocene sea level curve for the southeast coast of new south wales australia is presented based on a review of previously published geochronological results for fossil molluscs organi

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

matrix material in type 3 chondrites occurrence heterogeneity and relationship with chondrules abstract matrix material in type 3 chondrites forms rims on chondrules metal sulfide aggregates ca al rich inclusions and chondritic clasts it also forms lumps up to a millimeter in size which may contain coarser silicates chondrules of all types were found with internal matrix lumps that appear to have entered the chondrules before the latter had crystallized mean concentrations of mg na al and ca in matrix occurrences show up to fivefold variations in a single chondrite variations between mean matrix compositions of individual type 3 ordinary chondrites are almost as large and partly reflect systematic differences between h l and ll matrices such variations are probably a result of nebular separation of feldspathic material and ferromagnesian silicates compositions of chondrules and their matrix rims are normally unrelated although rim compositions are correlated with those of matrix lumps inside chondrules a single chondrule was found with a composition nearly identical to that of its internal matrix lump suggesting that some chondrules may have formed from matrix material matrix lumps are as heterogeneous as chondrules but mean chondrule and matrix compositions differ even allowing for possible loss of metallic fe ni during chondrule formation since bulk compositions of matrix lumps and rims have probably not changed significantly since their formation except for fe mg exchange our matrix samples cannot represent typical chondrule precursor materials

a 1500 yr record of north atlantic storm activity based on optically dated relict beach scarps understanding of long term dynamics of intense coastal storms is important for determining the frequency and impact of these events on sandy coasts we use optically stimulated luminescence osl dates on relict scarps within a prograded barrier sequence to reconstruct the chronology of large magnitude erosional events in the western gulf of maine osl dates obtained on quartz rich sediments immediately overlying relict scarps indicate severe beach erosion and retreat due to erosional events ca 1550 390 290 and 150 cal yr b p our data provide new evidence of increased storm activity most likely frequency and or intensity of extratropical storms during the past 500 yr which was preceded by a relatively calm period lasting 1000 yr the width of the coastal sequence preserved between successive paleoscarps shows strong correlation with the time interval elapsed between storms our fi ndings indicate that diagnostic geophysical and sedimentological signatures of severe erosional events offer new opportunities for assessing the impact and timing of major storms along sandy coasts

optically stimulated luminescence dating of sediments over the past 200 000 years optical dating of sediment using optically stimulated luminescence has become important for studying earth surface processes and this technique continues to develop rapidly a group of closely linked luminescence methods can be used to estimate the time since grains of quartz and feldspar were last exposed to daylight by detecting their subsequent response to environmental ionizing radiation exposure the technique is well suited to the dating of deposits as young as one year to several hundred thousand years recent technical developments have established a dating protocol with improved precision a high degree of reliability and an in built means to detect incomplete signal removal during deposition this approach has been extended to age estimation for single grains opening up a wider range of potential environments and new possibilities for understanding postdepositional grain movement ongoing research offers the possibility of significant age range extension and novel applications including low t

holocene evolution of the wave dominated embayed moruya coastline southeastern australia sediment sources transport rates and alongshore interconnectivity abstract sediment budgets on wave dominated coastlines are important in determining shoreline behaviour and are primarily inherited from geological scale coastal evolutionary history sediment compartments provide a framework to conceptualise and investigate sediment budgets over a range of time and space scales this study aims to assess the sediment budget for a secondary coastal compartment on the new south wales nsw south coast 26 km in length and containing five adjacent but discrete holocene coastal bay barriers barlings beach broulee beach bengello beach moruya heads beach and pedro beach building on earlier morphostratigraphic studies a new series of optically stimulated luminescence osl ages are presented for foredune ridge sequences at previously un dated sites additional ground penetrating radar gpr transects complement earlier stratigraphic datasets and seamless topographic and bathymetric lidar datasets provide insight into subaerial coastal deposits and inner shelf morphology in this region the results demonstrate that barriers within the compartment have two different sediment sources the barriers are dominated by shoreface supply of quartz rich sand transported onshore as shoreface morphology evolved towards equilibrium skeletal carbonate sand became an important component of the sediment budget for the northern barlings and broulee beaches after 3000 years ago shoreline progradation at bengello beach has been steady throughout the mid to late holocene bengello contains the largest volume of holocene sand and accreted at an average rate of 3 1 m3 m yr for the current shoreline length the other barrier systems have experienced changes in sediment accumulation rate as their shorelines prograded seaward resulting in changes to their alongshore interconnectivity rapid filling of the pedro beach embayment by 4000 years ago initiated headland bypassing and northward sand transport to moruya heads beach which only then commenced progradation in contrast as broulee and bengello beaches prograded they converged in the lee of broulee island forming a tombolo which led to division of the former continuous shoreline into two a marked increase in skeletal carbonate content at broulee occurred after this separation attesting to the restriction of the southern quartz sand source replaced by local carbonate production this study emphasises the importance of understanding the long term temporal variability in sediment budget and embayment interconnectivity in determining shoreline response to changing boundary conditions such as sea level and wave climate as well as contemporary anthropogenic influences

vertical sedimentation units in a barrier island washover fan overwash is a major component of a barrier island s response to high energy conditions examination of the 19 20 march 1975 storm deposits at assateague island showed that an overwash sequence could be divided into sedimentation units interpretation depends upon defining textural and mineralogical combinations that can be logically ordered as a vertical sequence if the sequence is depositional and formed from a single material normal grading usually results if polymineralogical and erosionally truncated inverse grading with a top layer of heavy minerals can be formed via an in situ sorting process dependent on disturbance depth and overwash influence

quantifying the error of 2d bulk chondrule analyses using a computer model to simulate chondrules simchon bulk chondrule compositions are important to many questions in cosmochemistry however the number of available bulk chondrule data sets is still small a main reason for this is the difficulties of determining bulk chondrule compositions a commonly used technique is to obtain 2d bulk chondrule compositions from meteorite sections this technique has an error that we quantify here for the first time using a mathematical model of a chondrule called simchon the theoretically calculated errors are compared to errors that we determined from serial sectioning of eight efremovka chondrules the errors obtained from both approaches are in excellent agreement proving that our mathematical model produces reliable errors that can be assigned to 2d bulk chondrule compositions these errors allow a much better interpretation of 2d bulk chondrule data we provide a table that contains typical errors for 2d bulk compositions of porphyritic chondrules the errors are in the range of 1 30 relative this should be acceptable for many problems in cosmochemistry the effect of a chemical layering inside chondrules and the occurrence of a rim around them as well as the occurrence of opaque and other accessory phases have been studied a spreadsheet is provided that enables the calculation of errors for any desired chondrule mineral composition bo chondrules have a negligible error but it is impossible to provide reasonable error estimates for bo chondrules with an igneous rim radial pyroxene chondrules have negligible errors

on the origin of late holocene sea level highstands within equatorial ocean basins abstract late holocene sea level highstands of amplitude 3 m are endemic to equatorial ocean basins these highstands imply an ongoing and moderate sub mm yr sea level fall in the far field of the late pleistocene ice cover that has long been linked to the process of glacial isostatic adjustment gia clark et al 1978 mitrovica and peltier 1991 coined the term equatorial ocean syphoning to describe the gia induced sea level fall and they provided the first physical explanation for the process they argued that water migrated away from far field equatorial ocean basins in order to fill space vacated by collapsing forebulges at the periphery of previously glaciated regions we provide a complete physical explanation for the origin of equatorial ocean syphoning and the associated development of sea level highstands using numerical solutions of the equation that governs meltwater redistribution on spherical viscoelastic earth models in particular we separate the total predicted sea level change into contributions associated with ice and meltwater loading effects and by doing so isolate a second mechanism that contributes significantly to the ocean syphoning process ocean loading at continental margins induces a levering of continents and a subsidence of offshore regions that has also long been recognized within the gia literature walcott 1972 we show that the influx of water into the volume created by this subsidence produces a sea level fall at locations distant from these margins indeed over the major ocean basins that is comparable in amplitude to the syphoning mechanism isolated by mitrovica and peltier 1991

the matrices of unequilibrated ordinary chondrites implications for the origin and history of chondrites abstract the matrices of sixteen unequilibrated ordinary chondrites all witnessed falls were studied microscopically in transmitted and reflected light and analyzed by electron microprobe selected specimens were also studied by scanning electron microscopy these studies indicate that the fine grained opaque silicate matrix of type 3 unequilibrated chondrites is compositionally mineralogically and texturally distinct from the chondrules and chondrule fragments and may be the low temperature condensate proposed by larimer and anders 1967 1970 examination of the matrices of unequilibrated chondrites also shows that each meteorite has been metamorphosed with the alteration ranging in intensity from quite mild where the matrix has been only slightly altered to a more severe metamorphism that has completely recrystallized the opaque matrix most of the metamorphic changes in the matrix occurred without significant effects on the compositions or textures of the chondrules the metamorphic alteration probably resulted from a combination of processes including thermal metamorphism and the passage of shock waves the present appearance of each unequilibrated chondrite is a result of the particular temperature and pressure conditions under which it and its components formed plus the subsequent metamorphic alteration it experienced

the barrier island system abstract barrier islands are part of a major coastal system composed of six interactive sedimentary environments the six environments are also elements needed to impose the designation barrier island on littoral sand bodies the elements are 1 mainland 2 backbarrier lagoon 3 inlet and inlet deltas 4 barrier island 5 barrier platform and 6 shoreface the morphodynamic and sedimentary evolution of each element affects adjacent environments as well as the entire system the interactive elements are defined and described by their morphologic sedimentologic and stratigraphic relationships to the barrier island and the barrier island system the stratigraphic relationships of the various elements of the system may be a valuable tool for paleogeographic reconstruction and sand body mapping

evidence for storm dominated early progradation of castle neck barrier massachusetts usa abstract washovers dune scarps and flattened beach profiles with concentrations of coarse grained sediment or heavy minerals are the diagnostic geological signatures of large storms on barriers today it is clear that storms are a major force driving transgressive barriers onshore but what is not as well understood is the role these powerful erosive events play in the evolution of prograding barriers application of ground penetrating radar gpr and a combination of coring techniques have significantly improved our ability to image barrier architecture results of these studies reveal a more complex evolution than previously recognized it is now possible to precisely locate and map storm deposits within prograded barrier lithosomes a comprehensive study of northern castle neck massachusetts was performed using 15 km of gpr surveys a 120 m long seismic line 11 cores and several radiocarbon dates storm related layers are the most prominent horizons contained in the barrier stratigraphy the geometry and sedimentology of these layers closely resembles those of a present day post storm beach twenty closely spaced curvilinear heavy mineral layers imaged in the landward portion of the barrier suggest that the castle neck barrier was heavily influenced by storms during its initial phase of progradation beginning 4000 years bp approximately 1800 years bp two intense storms impacted the coast depositing two extensive coarse grained units these layers mimic the flat lying sand and gravel deposits that occur in front of a nearby eroding till outcrop following major storms the great number of storm deposits in the early history of castle neck is related to either a period of greater storm activity and or a slow rate of barrier progradation the occurrence and preservation of these earlier storm layers are likely a product of the exposure of nearby drumlins resulting in greater availability of iron oxide and ferromagnesian sands the supply of heavy mineral sands has gradually diminished as the barrier prograded and the proximal drumlin source was buried by beach and dune sands

towards more robust chronologies of coastal progradation optically stimulated luminescence ages for the coastal plain at moruya south eastern australia accurate chronologies are fundamental for detailed analysis of palaeoenvironmental conditions archaeological reconstructions and investigations of holocene coastal morphological changes chronolog

chondrules matrix and coarse grained chondrule rims in the allende meteorite origin interrelationships and possible precursor components bulk compositions of 20 chondrules 13 coarse grained chondrule rims and two composite samples of matrix material from cv3 allende were determined by instrumental neutron activation analysis three rare nonporphyritic cv chondrules from allende leoville and vigarano were analyzed by broad beam electron microprobe analysis chondrule precursor components deduced from chondrule compositions are characterized by 1 refractory and semi refractory lithophiles with low feo 2 common siderophiles and chalcophiles 3 common to slightly volatile lithophiles si cr mn and modal pyroxene with moderately high feo feo mgo 4 moderately volatile siderophiles and 5 alkalies these precursor components can be explained by plausible processes occurring in the solar nebula the precursor components of coarsegrained rims are apparently the same as those of chondrules these components differ from those inferred previously for oc eh or cm co chondrules in general the compositions of coarse grained rims are more similar to the mean chondrule composition than to those of the chondrules they enclose rim siderophile contents are generally 2 5x greater than those in the chondrules and 0 5 to 2x those in bulk allende rims as a group are more homogeneous than chondrules suggesting that rims formed from finer grained precursors several chondrules and rims have fractionated rare earth patterns and may have been affected by metamorphism the enclosure of some coarse grained rims by fine grained matrix like rims that are almost certainly of nebular origin indicates that coarse grained rims were also formed in the nebula two matrix samples are similar in composition to some coarse grained rims suggesting that matrix was derived from similar compositional reservoirs of nebular dust chondrules with coarse grained rims were reheated in space following the accretion of dusty coatings this restricts plausible chondrule forming mechanisms to those that allow multiple nebular heating events

holocene palaeoecology and formation of the shoalhaven river deltaic estuarine plains southeast australia the shoalhaven river is one of the largest rivers on the south coast of new south wales and the deltaic estuarine plains associated with its mouth represent a mature stage of infill of a barrier estuary the stratigraphy of sediments from more than 60 drillholes from the plains indicates that the area has infilled during the mid holocene as a result of input of marine sands associated with a sand barrier on the high energy coast and fluvial mud and sands from the shoalhaven river molluscan assemblages indicate that marine influence was initially widespread throughout the eastern and southern parts of the embayment and that most of the plains infilled under estuarine conditions prominent levees across the plains surface are interpreted to be part of a birdsfoot delta distributary complex and individual floodbasins accreted progressively as they were encapsulated by distributary extension these former tidal environments mean that there are extensive potential acid sulphate soil conditions beneath the

the interrelation and distinction between flood tidal delta and washover deposits in a transgressive barrier island abstract the distinction and interrelation between flood tidal delta and washover deposits is described by comparing back barrier sands associated with an active and a relict tidal inlet system on the south shore of long island guidelines for comparison include three dimensional morphology sedimentary structures sediment texture and facies sequences the active modern flood tidal delta is covered by reversing small scale ripples represented by bidirectional small scale cross bedding in the subsurface large scale flood oriented cross beds are associated with non reversing sand waves on the flood ramp the relict flood tidal delta is represented by medium to fine grained sands characterized by small scale cross bedding or massive bedding relict flood tidal delta deposits are overlain by distinct washover deposits separated by thin units of salt marsh peat dominant washover structures are parallel laminations well preserved roots are commonly found in washover sands but are largely absent in flood tidal delta sands facies sequences of the relict inlet system indicate that flood tidal delta deposits extend the width of the barrier island overwashing serves to infill abandoned channels of the delta and contributes to vertical buildup

influence of climate fluctuations and changes in catchment land use on late holocene and modern beach ridge sedimentation on a tropical macrotidal coast keppel bay queensland australia abstract beach ridges at keppel bay central queensland australia preserve a record of sediment accumulation from the historical period back to middle holocene times the ridges comprise fine well sorted feldspar rich quartz sand that was eroded from the fitzroy river catchment deposited in keppel bay during floods of the fitzroy river and reworked onshore into beach and foredune deposits by the prevailing currents waves and wind these floods have an average recurrence interval of at least 7 yr and are induced by the passage of cyclones onshore into the large fitzroy catchment the youngest series of beach ridges sit sub parallel to the modern beach and comprise six accretional units each unit formed by a set of ridges and delineated by prominent swales optically stimulated luminescence osl ages of beach ridges in these units indicate they were deposited in periods of rapid progradation approximately 1500 1000 450 and 230 yr bp when there was an enhanced supply of sediment to the beach from the fitzroy river via keppel bay estimates of the mass of sediment stored in the beach ridge strandplain show that it represents a significant sediment store potentially trapping the equivalent of 79 of the estimated long term 100 yr average annual bedload of the fitzroy river that is deposited in keppel bay there has been a reduction in the rate of sediment accumulation in the strandplain since around 1000 yr bp which is consistent with other coastal records in eastern australia of a relatively wetter phase of climate in the late holocene compared to the present the youngest beach ridges osl ages

trace elements in rims and interiors of chainpur chondrules trace elements were measured in the rims and interiors of nine chondrules separated from the chainpur ll 3 chondrite whole rock samples of chainpur and samples of separated rims were also measured chondrule rims are moderately enriched in siderophile and volatile elements relative to the chondrule interiors the enriched volatile elements include the lithophilic volatile element zn the moderate enrichment of volatiles in chondrule rims and the lack of severe depletion in chondrules can account for the complete volatile inventory in chainpur these results support a three component model of chondrite formation in which metal plus sulfide chondrules plus rims and matrix silicates are mixed to form chondrites

integrating millennial and interdecadal shoreline changes morpho sedimentary investigation of two prograded barriers in southeastern australia abstract prograded barriers are distinctive coastal landforms preserving the position of past shorelines as low relief shore parallel ridges composed of beach sediments and commonly adorned with variable amounts of dune sand prograded barriers have been valued as coastal archives which contain palaeoenvironmental information however integrating the millennial timescale geological history of barriers with observed inter decadal modern beach processes has proved difficult technologies such as airborne lidar ground penetrating radar gpr and optically stimulated luminescence dating osl were utilised at boydtown and wonboyn in southeastern australia and combined with previously reported radiocarbon dates and offshore seismic and sedimentological data to reconstruct the morpho sedimentary history of prograded barrier systems these technologies enabled reconstruction of geological timescale processes integrated with an inter decadal model of ridge formation explaining the gpr imaged subsurface character of the barriers both the boydtown and wonboyn barriers began prograding 7500 8000 years ago when sea level attained at or near present height along this coastline and continued prograding until the present day with an initially slower rate of shoreline advancement sources of sediment for progradation appear to be the inner shelf and shoreface with a large shelf sand body likely contributing to progradation at wonboyn the towamba river seems to have delivered sediment to twofold bay during flood events after transitioning to a mature estuarine system sometime after 4000 cal yr bp some of this material appears to have been reworked onto the boydtown barrier increasing the rate of progradation in the seaward 50 of the barrier deposited over the past 1500 years the gpr imaged beachfaces are shown to have similar geometry to beach profiles following recent storm events and a model of ridge formation involving cut and fill of the beachface and dune building in the backshore explains the character of the preserved beachface record and the morphology of the ridges this model is applicable to future management of individual beaches where such beaches are subject to ongoing cut and fill dune building processes and inherited sediment budget conditions

chondrules and matrix in the ornans co3 meteorite possible precursor components abstract bulk compositions of 17 chondrules and one sample of matrix from co3 omans were determined by instrumental neutron activation analysis chondrule precursor components deduced from chondrule compositions are characterized by 1 1 common and slightly volatile siderophiles cr and chalcophiles 2 2 refractory lithophiles and na 3 3 mn si and modal pyroxene and 4 4 feo and olivine component 4 may be closely related to matrix material precursor components have now been inferred for oc eh cv cm and co chondrules a mn and si rich component occurs exclusively among carbonaceous chondrite chondrules although there are significant intergroup differences common to chondrules in all chondrite groups are refractory lithophile rich common siderophile rich and with the exception of eh common lithophile rich components this indicates that the siderophile lithophile and refractory lithophile common lithophile fractionations recorded in chondrite whole rocks were established prior to chondrule formation at all nebular locations

a review of wave dominated clastic shoreline deposits abstract barrier islands beaches wave dominated deltas and chenier plains probably form more than one fifth of present coasts and constitute an even larger proportion of the subsiding lowland coasts likely to be preserved in the stratigraphic record the geometry vertical sequences and composition of their deposits are the result of 1 shoreline behaviour whether transgressive regressive or stable 2 physical processes particularly the relative intensities of waves and tides 3 climate 4 global tectonic setting and 5 topography of underlying deposits published interpretations indicate that equivalent deposits are abundant in the geological record sandstones are mostly quartzose cemented by carbonates and quartz and have sheet or linear geometries ancient deposits can provide evidence of palaeogeography and some are economically significant particularly as hydrocarbon reservoir rocks four end member sedimentation models are proposed for the interpretation of ancient deposits 1 transgressive sheet sands associated with deltas 2 non deltaic transgressive sheet sands 3 regressive sheet sands and 4 linear sand bodies probable depositional settings geometries characteristics of deposits and palaeocurrent patterns are discussed

transgressive and regressive stratigraphies of coastal sand barriers in southeast australia abstract in recent years attempts have been made in southeast australia to document the stratigraphic characteristics of coastal sand barriers two basic arrangements of facies are distinguished those associated with transgressive depositional sequences and those associated with regressive sequences transgressive sequences either are formed during the postglacial marine transgression or are related to receding or transgressive barriers at present sea level in the former case complex interfingering of nearshore washover and lagoonal facies are evident in many areas these facies underlie those associated with regressive sequences which have formed since sea level has reached its present position ca 6000 6500 yrs ago examples of regressive sequences associated with both prograded and stationary barrier types occur in southeast australia here the thickness of nearshore facies in particular is commonly greater than equivalent units beneath barriers on coasts of lower energy and for less steep inner shelf gradients in the northern hemisphere the interplay of various factors within embayments has led to the development of several barrier types such as prograded stationary receded and episodic dune with some sedimentary characteristics in common with similar types recognized in other parts of the world e g texas delaware the netherlands barriers formed as a result of migrating spits and tidal inlets are not common in southeast australia

post glacial sea level changes around the australian margin a review abstract it has been known since rhodes fairbridge s first attempt to establish a global pattern of holocene sea level change by combining evidence from western australia and from sites in the northern hemisphere that the details of sea level history since the last glacial maximum vary considerably across the globe the australian region is relatively stable tectonically and is situated in the far field of former ice sheets it therefore preserves important records of post glacial sea levels that are less complicated by neotectonics or glacio isostatic adjustments accordingly the relative sea level record of this region is dominantly one of glacio eustatic ice equivalent sea level changes the broader australasian region has provided critical information on the nature of post glacial sea level including the termination of the last glacial maximum when sea level was approximately 125 m lower than present around 21 000 19 000 years bp and insights into meltwater pulse 1a between 14 600 and 14 300 cal yr bp although most parts of the australian continent reveals a high degree of tectonic stability research conducted since the 1970s has shown that the timing and elevation of a holocene highstand varies systematically around its margin this is attributed primarily to variations in the timing of the response of the ocean basins and shallow continental shelves to the increased ocean volumes following ice melt including a process known as ocean siphoning i e glacio hydro isostatic adjustment processes several seminal studies in the early 1980s produced important data sets from the australasian region that have provided a solid foundation for more recent palaeo sea level research this review revisits these key studies emphasising their continuing influence on quaternary research and incorporates relatively recent investigations to interpret the nature of post glacial sea level change around australia these include a synthesis of research from the northern territory queensland new south wales south australia and western australia a focus of these more recent studies has been the re examination of 1 the accuracy and reliability of different proxy sea level indicators 2 the rate and nature of post glacial sea level rise 3 the evidence for timing elevation and duration of mid holocene highstands and 4 the notion of mid to late holocene sea level oscillations and their basis based on this synthesis of previous research it is clear that estimates of past sea surface elevation are a function of eustatic factors as well as morphodynamics of individual sites the wide variety of proxy sea level indicators used their wide geographical range and their indicative meaning some progress has been made in understanding the variability of the accuracy of proxy indicators in relation to their contemporary sea level the inter comparison of the variety of dating techniques used and the nuances of calibration of radiocarbon ages to sidereal years these issues need to be thoroughly understood before proxy sea level indicators can be incorporated into credible reconstructions of relative sea level change at individual locations many of the issues which challenged sea level researchers in the latter part of the twentieth century remain contentious today divergent opinions remain about 1 exactly when sea level attained present levels following the most recent post glacial marine transgression pmt 2 the elevation that sea level reached during the holocene sea level highstand 3 whether sea level fell smoothly from a metre or more above its present level following the pmt 4 whether sea level remained at these highstand levels for a considerable period before falling to its present position or 5 whether it underwent a series of moderate oscillations during the holocene highstand

transition from marine to fluvial dominated sediment supply at shoalhaven prograded barrier southeastern australia abstract prograded barriers are depositional coastal landforms which have the potential to reveal changes in the primary drivers of coastal evolution within their varied morphology beach ridges and intervening swales preserve paleoenvironmental records of coastal processes relative sea level and storm events optically stimulated luminescence osl dating of quartz grains airborne lidar derived morphology and sediment texture and mineralogy reveal four different periods of morpho sedimentary progradation history in the shoalhaven barrier system in southeastern australia the barrier is composed of approximately 40 ridges that occupy an area of 15 2 km2 comprising an estimated sand volume of approximately 88 000 000 m3 above mean sea level osl dating of ten samples taken from a 940 m long transect across the holocene system indicated that the barrier prograded at a slow rate of approximately 0 12 m yr from 6130 330 to 2400 130 years ago and subsequently at a higher rate of 0 22 m yr until 600 130 years ago more recently an increase in historical accumulation and progradation rates has favoured development of an anomalously high foredune fronting the system with the formation of lower ridges in the past two centuries increasing angularity and feldspar content observed via scanning electron microscope sem and determined using x ray diffraction xrd analysis respectively imply a transition in sediment supply progradation has been sustained through delivery and reworking of marine sediments from offshore following the marine transgression subsequently augmented by fluvial sands discharged to the coast by the shoalhaven river the adjustment in progradational rates and sediment provenance influenced the morphology and spacing of individual ridges and the regressive system as a whole average progradation rates for the shoalhaven barrier revised from those previously reported using radiocarbon dating are considered lower than most of barriers studied in similar coastal environments around australia indicating the different ways that similar progradation systems have evolved

holocene coastal evolution of the transition from transgressive to regressive barrier in southern brazil abstract in this study the evolution of a holocene coastal barrier was determined based on a basal transgressive unit followed by a regressive unit standard penetrating test vibrocore and ground penetrating radar profiles were used to acquire stratigraphic data sedimentological paleontological and geochronological analyses were performed to describe and interpret the sedimentary facies the base of the holocene record indicates the existence of pre transgression continental and coastal environments basal peat which resulted from the initial flooding of the antecedent topography pleistocene substrate due to rising sea levels during this period the continental environments were flooded by lagoon environments that occupied the landward displacement of the transgressive barrier which had channels that connected the lagoon and the ocean at this time the coastal barrier had a transgressive configuration indicated by its morphology and characterized by washover fans as the backbarrier accommodation space decreased due to the displacement of the barrier transgressive maximum the transition of the transgressive regressive record began at approximately 7 200 years bp restricting the overwash events and the dynamics of the inlets however before the highest level eustatic maximum of the postglacial marine transgression pmt was reached this transgressive barrier stopped its migration toward the continent causing an inversion of the depositional record which became a normal regression later at the end of the pmt sea levels began to fall causing a forced regression that persists to the present day

compositions and textures of relic forsterite in carbonaceous and unequilibrated ordinary chondrites several percent of the olivine in the c2 c3 and unequilibrated ordinary chondrites uoc can be distinguished by blue cathodoluminescence cl and an unusual composition for forsterite this olivine has the following textural features 1 1 forms cores in single olivine grains 2 2 shows subhedral to euhedral boundaries against rim olivine 3 3 rarely contains inclusions 4 4 has embayments containing olivine like that of the rim 5 5 occurs within chondrules especially in uoc meteorites the blue olivine is always fe poor 0 25 feo 1 0 and shows the following average and maximum values al2o3 0 25 0 5 tio2 0 05 0 09 cao 0 5 0 8 cr2o3 0 15 0 5 and mno 0 02 0 15 vanadium is present within a single olivine and within all blue olivines al ca and ti are strongly positively correlated as are mn fe and cr in olivine surrounding the blue the blue cores are not zoned but each element shows a marked change at the boundary of the blue with al showing the most rapid change these are interpreted as diffusion profiles between rim and core olivine textures suggest initial free growth probably from a gas and later addition of olivine by liquid crystallization to form single crystals or chondrules the unusual olivine composition indicates high temperature growth from a refractory rich reservoir with al entering olivine in tetrahedral coordination vapor growth is suggested as the process allowing the high minor element levels the occurrence of blue olivine in all primitive meteorites indicates that it is relic material which was widespread prior to chondrule and hence meteorite formation similarities in composition exist between this relic olivine and olivine of cosmic dust and deep sea particles pointing to this olivine being a common component in all primitive extraterrestrial material

the evolution of coastal barrier systems a case study of the middle late pleistocene wilderness barriers south africa abstract barrier systems contain lengthy but complex records of long term environmental fluctuations the wilderness embayment south africa contains a system of shore parallel barriers reaching up to 200 m above modern sea level this study reports the results of chronological topographical both on and off shore sedimentological and micromorphological analyses within the wilderness embayment sixty one new luminescence ages from sixteen sites in unconsolidated dunes and three separate barriers are presented which when combined with previously published luminescence ages from the area provide a high resolution chronological framework for the emplacement and evolution of the barrier system the preserved barriers have been constructed within at least the last two glacial interglacial cycles with notable phases between 241 221 ka 159 143 ka 130 120 ka 92 87 ka and post 6 ka multiple phases of barrier construction occurred during sea level highstands with sediment deposition on each individual barrier occurring over at least two interglacials holocene evolution of the system sheds light on earlier events with dune preservation occurring only during early regression from the mid holocene highstand tectonic stability at wilderness allowed glacio eustatically formed shorelines to occupy similar positions on multiple occasions this in conjunction with a relatively humid climate and a well vegetated landscape enabled deflated sediment from beaches to form dunes which stacked upon each other to form an extensive and complex vertical accretionary sequence repeated erosion and recycling of pre existing barriers as well as barrier construction on what is currently the off shore platform during still stands in sea level regressional cycles when sea levels dropped below ca 50 m from the present day has added to the complexity of the preserved terrestrial barrier record the wilderness barrier system contrasts with barriers developed elsewhere in the world where higher rates of crustal uplift have allowed preservation of a more complete and more widely spaced palaeorecord this research also shows the utility of integrating off shore topography as revealed by bathymetry with terrestrial topographic data for the better understanding of the evolution of palaeo coastlines and the preserved dune record found on present day coastal plains local variation in the topography of the continental shelf at wilderness has generated spatial and temporal complexity within the sedimentary records of individual barriers as well as having a significant influence on preservation

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

origins of holocene coastal strandplains in southeast australia shoreface sand supply driven by disequilibrium morphology abstract coastal barriers store depositional records of past environmental conditions such as sea level wave climate and sedimentary regime the embayed highstand coast of southeast australia features a diverse range of coastal sand barriers suggesting varying depositional responses to holocene environmental conditions in particular the varying chronologies of prograded barrier strandplains along a passive margin with a predominantly autochthonous sedimentary regime raises questions about relative sea level change and sediment sharing within and between compartments during the holocene here we apply detailed geological data and geochronology from the holocene prograded barrier system at tuncurry within a morphodynamic modelling approach to investigate the depositional response of the coastal system to possible drivers of strandplain growth including 1 forced regression driven by mid to late holocene relative sea level fall 2 time varying external sand supply via the alongshore transport system and 3 shoreface sand supply in response to disequilibrium morphology and stable sea level comparison between the simulated depositional response of the coastal system and the geological records suggests that progressively weakening and depth decaying shoreface sand supply in response to disequilibrium morphology was the primary driver of holocene strandplain growth alongshore sand transport into the tuncurry compartment via a headland attached shelf sand body may have provided a secondary sand source although the simulated barrier shoreface evolution precludes a dominant external sand supply mid to late holocene sea level fall from a highstand level within the range of uncertainty in available indicators 1 5 m above present could only have contributed a minor portion of strandplain growth by process of forced regression the simulations demonstrate the potential sensitivity of strandplain chronologies to the sampling location i e shoreface or dune facies which emerges from coupled barrier shoreface evolution that may support time decaying volumetric growth and steady shoreline progradation simultaneously shoreface sand supply driven by the ongoing relaxation of disequilibrium morphology may persist at subtle rates 1 2 m3 m yr today on some southeast australian beaches promoting shoreline stability and potentially moderating initial shoreline response to sea level rise

osl based lateral progradation and aeolian sediment accumulation rates for the apalachicola barrier island complex north gulf of mexico florida article i nfo vertical sediment cores in five separate beach ridge complexes along the north east gulf of mexico coast were recovered and dated using optically stimulated luminescence osl dating of quartz these are located on cape san blas csb little st george island lsgi richardson s hammock rh st joseph peninsula sjp and saint vincent island svi all of these landforms are coastal barrier systems situated along a 100 km stretch of the florida panhandle u s a two samples were collected for dating from each core ridge accumulation rates rar associated with lateral progradation were calculated from the dated samples we also determined average sediment accumulation rates asar for two intervals within each sediment core all osl ages within the sediment cores were found to be in stratigraphic order or in a few cases statistically indistinguishable moreover all dated ridges were found to be in correct temporal sequence based on their geomorphic positions rapidly accreted sequences were found to be backed by st joseph bay in the western region of the study area more slowly accreted sequences were associated with the more eastern stretches of the study area backed by st vincent sound and apalachicola bay our asar results are in accord with an australian study of modern dune accumulation perhaps our most important finding is that in the barrier island environments of this north eastern gulf coast region aeolian sedimentation continues well after full vegetative cover develops and stranding of landward ridges takes place this confirms our similar earlier observation on svi lopez and rink 2008 we find that up to approximately one order of magnitude lower sedimentation rates occur after an initial period of more rapid aeolian accumulation for the vertical intervals studied in foredune ridges lateral progradation rates of ridge sequences were highly variable within the study area ranging from 92 to 848 m 100 years but we did find agreement between some of our slower ridge accumulation rates and those in other areas of florida and around the world determined using osl and 14 c dating we conclude that osl may be used in a regional context to establish variation in progradation rates and aeolian accumulation that varies among systems

depositional controls on a hypertidal barrier spit system architecture and evolution pointe du banc spit north western france physical stratigraphy architecture and evolution of barrier systems in hypertidal environments tidal range above 6 m are understudied and depositional controls are poorly understood compared with wave dominated barrier systems and barrier spits in microtidal mesotidal and macrotidal settings based on vibracores ground penetrating radar radiocarbon and optically stimulated luminescence age data the formation and evolution of the hypertidal barrier system of pointe du banc north western france has been reconstructed the study shows that the barrier spit has a complex composite sedimentary architecture consisting of wave dominated and tide dominated sedimentary bodies a morpho sedimentary model is presented that demonstrates how barrier spit progradation resulting from littoral drift was the main manner of spit elongation whereas sediment convergence caused by landward migration of swash bars and seaward migration of tidal dunes caused the spit terminus to grow in height and width these results suggest that long term accretion rates varied considerably in response to changes in sediment supply variations in storminess together with the large scale topography of the coast controlled the sediment supply and thus the evolution of the barrier system during latest holocene despite architectural complexity hypertidal barrier systems preserve records of past climate changes

chondrules and other components in c o and e chondrites similarities in their properties and origins we describe three types of chondrules that are common to h3 ll3 cm2 co3 and cv3 chondrites low and high feo porphyritic olivine chondrules contain olivine with fa0 3 8 and fa5 50 respectively and can easily be distinguished petrographically poikilitic pyroxene chondrules have 1 20 vol olivine fa0 2 8 enclosed by low ca pyroxene fs0 5 7 and also occur in e chondrites these three types formed in separate nebular regions which had dimensions and spacings such that a few percent of the chondrules that collided to form compound chondrules were of different types sorting of chondrule precursor material and mixing of chondrule types probably account for most variations in bulk and mineral chemistry among chondrite groups metallic fe ni grains containing 0 1 1 cr si and p are present in low feo olivine chondrules from all type 2 and least metamorphosed type 3 chondrites metal compositions reflect reduction during chondrule formation in the nebula not nebular condensation opaque matrices in type 3 ordinary and carbonaceous chondrites are somewhat similar in composition and mineralogy and probably have related origins we conclude that chondrules in all known chondrite groups share similar nebular origins

evolution from estuary to delta alluvial plain morphology and sedimentary characteristics of the shoalhaven river mouth southeastern australia abstract the shoalhaven river in southern new south wales nsw drains a catchment of 7000 km2 forming a barrier estuary at its mouth with a prograded strandplain to its north previous coring and dating across the floodplain and adjacent strandplain indicate progressive infill of the estuarine basin over the past 7000 years over this time the system transitioned from a wave dominated estuary to a wave dominated delta the shoalhaven river appears to have initially discharged to the sea at crookhaven heads until it adopted a more direct route through an intermittently open mouth at shoalhaven heads construction of berrys canal in 1822 now permanently links the shoalhaven river to the adjacent smaller crookhaven river airborne lidar reveals details of topography of prominent levees and meander scroll bars that flank the lower reaches of the river and beach foredune ridges to the north sedimentological and mineralogical characteristics of modern sediment samples collected from the river channel the beach and the barrier reveal that the shoalhaven river is dominated by quartz sand along its predominantly straight course through the infilled estuarine plains this is in contrast to the tripartite classification of sedimentary depositional environments comprising sandy fluvial delta central mud basin and sandy marine barrier that characterised the initial wave dominated estuary 7000 years ago and is typical of most barrier estuaries in nsw grain size decreases downstream and sands have a higher feldspar content and angularity than is typical of marine sand that has been reworked in the nearshore this fluvially derived component is delivered to the coast intermittently by floods that re open shoalhaven heads as shown by retrospective analysis of aerial photography and satellite imagery grain size decreases with distance alongshore from the river mouth indicating that these sands are transported north by longshore drift to augment a gradual onshore delivery of sand within this coastal compartment scanning electron microscopy of selected grains implies that this fluvial sand has been contributing to incremental formation of beach ridges for much of the past 3000 years since the estuarine basin has been largely infilled with a slight detectable acceleration in the rate of progradation

transition of a regressive to a transgressive barrier island due to back barrier erosion increased storminess and low sediment supply bogue banks north carolina usa abstract although back barrier erosion is a prevalent process of island narrowing it is often overlooked in conceptual models of barrier island evolution in many wave dominated barrier island settings the absence of overwash precludes landward movement of the back barrier shoreline and hence the island as a whole from sustaining its width typically regressive barriers are wide and exhibit high elevations with the most seaward dune ridge possessing the highest elevation this morphology may prevent overwash and inlets from breaching the barrier and therefore the associated sediment from reaching the back barrier shoreline for millennia back barrier shoreline erosion from sea level rise and storms can be permanent in the absence of sediment supply from rivers overwash and inlet processes with continued narrowing and lowering of the island regressive barriers may reach a critical state making overwash and inlet formation imminent and transitioning the island to a transgressive barrier the modern day morphologic variability along the 40 km long island of bogue banks north carolina includes both regressive and transgressive segments making this setting ideal for examining whether the transition between these barrier island types is gradual or threshold driven bogue banks consists of two discrete segments characterized by high elevation beach ridges large island widths and stratigraphy consistent with regressive barrier islands these regressive island segments are separated by a broad narrow section of the island devoid of any washover fans flood tide deltas or other transgressive elements analyses of seismic data from the inner continental shelf reveal paleochannels intersecting the wide sections of the island while the narrow central part of the island occupies an inter fluvial area reworking of fluvial sediment from paleochannels was an important sediment source for the barrier during regression optically stimulated luminescence osl dates from the most landward beach ridges constrained initiation of island regression at 3000 cal yr bp close to when there was a significant decrease in the rate of relative sea level rise from 5 mm yr to 0 8 mm yr transects of cores seismic data ground penetrating radar data and radiocarbon and osl dates show that prior to 1500 cal yr bp the central narrow section of the island was wide and progradational similar to adjacent areas back barrier erosion of the central part of the barrier primarily caused island narrowing as a result of increased storminess which occurred around the medieval climate anomaly 1100 cal yr bp this part of the island was more vulnerable to erosion than adjacent areas due to increased bay ravinement bogue sound is widest there and its lower elevation farther away from paleochannel sediment source relict inlet channels exist along the central portion of the island formed within the last 250 yr and likely closed shortly after formation the presence of historical inlets along the narrow central section of the island indicates bogue banks may be nearing a critical width threshold and will subsequently transition to a transgressive barrier because the change in barrier morphology associated with back barrier erosion occurred over a period of time when the rate of sea level rise was relatively low low sediment supply and increased storm frequency are shown to be the main forcing mechanisms of island narrowing these impacts in addition to a predicted increase in sea level rise rates and human modifications e g maintenance of a high elevation foredune closing of inlets prevention of island overwash and associated sediment delivery to the back barrier shoreline will likely promote rapid transition of regressive barrier islands to those dominated by transgressive processes

internal structure of a barrier beach as revealed by ground penetrating radar gpr chesil beach uk abstract chesil beach dorset is one of the most famous coastal landforms on the british coast the gravel beach is over 18 km long and is separated for much of its length from land by a tidal lagoon known as the fleet the beach links the isle of portland in the east to the mainland in the west despite its iconic status there is little available information on its internal geometry and evolutionary history here we present a three fold model for the evolution of chesil beach based on a series of nine ground penetrating radar gpr traverses located at three sites along its length at abbotsbury langton herring and at ferry bridge the gpr traverses reveal a remarkably consistent picture of the internal structure of this barrier beach the first phase of evolution involves the landward transgression of a small sand and gravel beach which closed upon the coast leading to deposition of freshwater peat between 5 and 7 k yr bp the second evolutionary phase involves the bulking out of the beach during continued sea level rise but in the presence of abundant gravel supplied by down drift erosion of periglacial slope deposits this episode of growth was associated with a series of washover fans which accumulated on the landward flank of the barrier increasing its breadth and height but without significant landward transgression of the barrier as a whole the final phase in the evolution of chesil beach involves the seaward progradation of the beach crest and upper beach face associated with continued sediment abundance but during a still stand or slight fall in relative sea level this phase may provide further evidence of a slight fall in relative sea level noted elsewhere along the south coast of britain and dated to between 1 2 and 2 4 k yr bp subsequently the barrier appears to have become largely inactive except for the reworking of sediment on the beach face during storm events the case study not only refines the evolutionary picture of chesil beach but illustrates the importance of the subtle interplay between relative sea level and sediment supply in the evolution of a barrier system in addition it also illustrates the potential of gpr in resolving the evolutionary history of gravel rich coastal landforms such as chesil beach

matrices of type 3 ordinary chondrites primitive nebular records petrologic studies were made on the fine grained matrices of type 3 ordinary chondrites of the lowest petrologic subtype the matrix minerals in order of abundance are olivine fo99 to fo9 enstatite or bronzite augite or subcalcic augite albite fe ni metal troilite magnetite spinel mgal2o4 chromite and calcite fe and mg rich fluffy particles and albite like particles are also major constituents the chemical compositions of olivine and pyroxenes vary within and among the chondrites and are in gross disequilibrium showing that the matrix materials were hardly heated after their formation textural relationships indicate that magnesian olivine was formed after ca pyroxene followed by intermediate to iron rich olivine intermediate olivine was formed from enstatite and metallic iron under relatively oxidizing conditions the observations indicate that matrices of chondrites are neither the fragments of chondrules nor the precursors of chondrules they were mostly the products of condensation and reaction among solids and or between solids and the ambient gas mostly at low temperatures and thus they contain records of primitive processes in the nebula in order to explain the presence of olivines more iron rich than fo50 the presence of free sio2 or a high activity of sio2 in the gas is necessary which was not shown in previous thermochemical calculations mineral assemblages of matrix minerals of chondrites of different chemical groups differ systematically according to oxidation state of the parental meteorites indicating that they were formed at different oxygen fugacities the rims of chondrules and surrounding matrix materials must have accreted onto chondrules during turbulent movements of the nebula

the origin and history of the metal and sulfide components of chondrules abstract fourteen siderophile and other non lithophile elements determined in 31 semarkona ll3 0 chondrules by neutron activation analysis are severely fractionated relative to lithophile elements their chondrule whole rock abundance ratios vary by factors of up to 1000 the mean ratio is 0 2 non refractory siderophile abundance patterns in ni rich chondrules are smooth functions of volatility and in ni poor chondrules patterns are more irregular refractory siderophile elements are often fractionated from ni they covary confirming the presence of a refractory metal component the chalcophile element se correlates with br and siderophile elements zinc is uniformly low and uncorrelated with other elements most metal and sulfide in chondrules was probably present in the solar nebula before chondrule formation most siderophile and chalcophile elements were in these materials some fe was also in silicates as were minor amounts of ni co au ge and possibly se the amount of metal formed by reduction during chondrule melting was minor the common metal component in chondrules is similar to and may be the same as the common component involved in the metal silicate fractionation of the ordinary chondrite groups chondrules are depleted in metal chiefly because they sampled metal poor precursor assemblages metal segregation during the molten period and subsequent loss was a minor process that may be responsible for most surface craters on chondrules

erosional and depositional characteristics of regional overwash deposits caused by multiple hurricanes regional scale washover deposits along the florida gulf and atlantic coasts induced by multiple hurricanes in 2004 and 2005 were studied through coring trenching ground penetrating radar imaging aerial photography and prestorm and poststorm beach profile surveys erosional and depositional characteristics in different barrier island sub environments including dune field interior wetland and back barrier bay were examined over the eroded dune fields the washover deposits are characterized by an extensive horizontal basal erosional surface truncating the old dune deposits and horizontal to slightly landward dipping stratification over the marshes in the barrier island interior the washover deposits are characterized by steep tabular bedding with no erosion at the bottom overwash into the back barrier bay produced the thickest deposits characterized by steep prograding sigmoidal bedding no significant erosional feature was observed at the bottom washover deposits within the dense interior mangrove swamp demonstrate both normal and reversed graded bedding the washover deposits caused by hurricanes frances 2004 and jeanne 2004 along the southern florida atlantic coast barrier islands are substantially different from those along the northern florida barrier islands caused by ivan 2004 and dennis 2005 in terms of regional extension erosional features and sedimentary structures these differences are controlled by different overall barrier island morphology vegetation type and density and sediment properties the homogeneity of sediment along the northern florida coast makes distinguishing between washover deposits from ivan and dennis difficult in contrast along the atlantic coast barrier islands the two overwash events as demonstrated by two phases of graded bedding of the bimodal sediments are easily distinguishable

evidence for primitive nebular components in chondrules from the chainpur chondrite abstract the least equilibrated ordinary chrondrites contain chondrules which have experienced little change since the time of their formation in the early solar system these chondrules are excellent indicators of the physical and chemical nature of the solar nebula we separated 36 chondrules from the chainpur ll3 4 chondrite and analyzed each for 20 elements and petrographic properties sampling biases were minimized as far as possible chondrules seem to have formed through the melting of random mixtures of grains comprising a limited number of nebular components the identity of these components can be deduced from chondrule compositions the dominant components appear to be 1 a mixture of metal and sulfide with composition similar to whole rock metal and sulfide 2 refractory ir rich metal 3 refractory olivine rich silicates 4 low temperature pyroxene rich silicates and possibly 5 a component containing the more volatile lithophiles most of the textural types of chondrules formed from the same set of precursor components in some cases chondrules having different textures are almost identical in composition a few unusual chondrule types seem to mainly consist of uncommon nebular components possibly indicating different modes of formation etching experiments confirm that chondrule rims are enriched in metal troilite and moderately volatile elements relative to the bulk chondrules however a large fraction of the volatiles remains in the unetched interior

stratigraphy of washover deposits in florida implications for recognition in the stratigraphic record abstract twelve washover deposits were cored on the west central gulf coast of florida to provide data to permit development of a model to help identify washover facies in the stratigraphic record typical modern washover stratigraphy displays landward dipping plane beds comprised of well sorted sand with distinct laminae of shells and heavy minerals five subfacies are delineated which show variations in composition texture and bioturbation throughout the washover facies these subfacies represent differences in flow conditions during overwash position relative to sea level and variable degrees of reworking after deposition three shell assemblages aid in identification of washover deposits backbarrier sediments composed of shoreface open water species or mixed shoreface backbarrier species may potentially be washover in origin sediments with purely backbarrier quiet water shell species are likely to have been deposited independently of washover activity examination of washover deposits of differing ages reveals that preservation of washover stratigraphy is not exclusively a function of time reworking of small scale stratification can occur in as short as a decade however this same stratification was found to be preserved in deposits several hundred years old destruction of original washover signatures is related to the position of the deposits relative to sea level and the rate and depth of burial even after the destruction of small scale stratigraphic features washover deposits may still be identified as such due to their texture composition and shell assemblages key features in recognizing the facies after bioturbation and reworking are 1 the presence of clean sand in otherwise muddy backbarrier sediments 2 the landward thinning of the facies and 3 the presence of shoreface shells or mixed shoreface backbarrier shells on landward portions of the barrier island system if reworking is severe and or there are limited subsurface data distinguishing washovers from genetically similar deposits e g flood tidal deltas and spillover deposits in the stratigraphic record is difficult and when considered out of stratigraphic context may not be recognizable

an absolute chronology for the raised beach and associated deposits at sewerby east yorkshire england the raised beach sediments revealed in the cliffs at sewerby east yorkshire are widely regarded as ipswichian in age previously reported evidence for this dating is reviewed and new results from a range of luminescence dating techniques applied to the blown sand deposit overlying the raised beach are reported these provide the first absolute date for the sewerby site of 120 84 11 82 ka which places the blown sand at the boundary between oxygen isotope stages ois 5e and 5d as the underlying raised beach is little older than the blown sand it probably formed during ois stage 5e as suggested by the faunal evidence

optically stimulated luminescence dating of holocene relict foredunes guichen bay south australia abstract optically stimulated luminescence osl dating of quartz sand 106 150 or 150 200 m in bioclastic carbonate quartz sediments sampled from coastal relict foredunes beach ridges was undertaken to evaluate the utility of the osl method for studies of dune dynamics and to quantify rates of coastal progradation twelve sediment samples from a 4 km transect across a holocene embayment fill at guichen bay south australia were measured for their luminescence characteristics apart from one age inversion attributed to recent disturbance associated with mining the osl ages are in sequential order when considered in the context of their associated error terms the osl ages indicate an extremely rapid initial phase of sedimentation i e 1600 m within a few hundred years approximately 5 ka ago followed by a constant rate of progradation for the past 4 ka of 0 39 m a with a high level of association between distance across the embayment fill and luminescence age for this time interval an average rate of dune development of one dune every 80 yr from 3900 yr ago to the present day is apparent the osl ages for the late holocene indicate that the present beach state is largely in equilibrium with sediment supply

reply to the discussion by dillenburg et al on evidence for a transgressive barrier within a regressive strandplain system implications for complex response to environmental change

discussion evidence for a transgressive barrier within a regressive strandplain system implications for complex response to environmental change by hein et al 2013 sedimentology 60 469 502

coarse sand beach ridges at cowley beach north eastern australia their formative processes and potential as records of tropical cyclone history storm surges generated by tropical cyclones have been considered a primary process for building coarse sand beach ridges along the north eastern queensland coast australia this interpretation has led to the development of palaeotempestology based on the beach ridges to better identify the sedimentary processes responsible for these ridges a high resolution chronostratigraphic analysis of a series of ridges was carried out at cowley beach queensland a meso tidal beach system with a 3 m tide range optically stimulated luminescence ages indicate that 10 ridges accreted seaward over the last 2500 to 2700 years the ridge crests sit 3 5 to 5 1 m above australian height datum ca mean sea level a ground penetrating radar profile shows two distinct radar facies both of which are dissected by truncation surfaces hummocky structures in the upper facies indicate that the nucleus of the beach ridge forms as a berm at 2 5 m australian height datum equivalent to the fair weather swash limit during high tide the lower facies comprises a sequence of seaward dipping reflections beach progradation thus occurs via fair weather wave accretion of sand with erosion by storm waves resulting in a sporadic sedimentary record the ridge deposits above the fair weather swash limit are primarily composed of coarse and medium sands with pumice gravels and are largely emplaced during surge events inundation of the ridges is more likely to occur in relation to a cyclone passing during high tide the ridges may also include an aeolian component as cyclonic winds can transport beach sand inland especially during low tide and some layers above 2 5 m australian height datum are finer than aeolian ripples found on the backshore coarse sand ridges at cowley beach are thus products of fair weather swash and cyclone inundation modulated by tides knowledge of this composite depositional process can better inform the development of robust palaeoenvironmental reconstructions from the ridges this article is protected by copyright all rights reserved

sedimentary records of intense storms in holocene barrier sequences maine usa coastal morphological geophysical ground penetrating radar gpr and sedimentological data document extreme storm events along the sandy barriers of maine s south central hunnewell and flat point barriers and southwestern saco bay barriers coastal compartments the hunnewell barrier contains four equally spaced buried storm scarps behind the exposed scarp of the blizzard of 1978 a 100 year storm that eroded more than 100 m of shoreline causing extensive property loss these scarps dip 3 5j steeper than the normal beachface slope and consist of sands with more than 50 heavy minerals the heavy minerals produce distinct subsurface reflections that facilitate the location of buried supratidal parts of storm scarps and the mapping of ancient poststorm shoreline positions the imaged scarps likely formed within the past 1 5 2 0 ka bp the flat point barrier consists of a prograded sequence overlain by a laterally extensive seaward thinning layer of freshwater peat and capped by aeolian sands this stratigraphy suggests that the bog varied in size through time contracting during overwash events and aeolian deposition and expanding across washover sheets during extended periods of barrier stability the main overwash event accompanied by barrier planation and wetland expansion may be linked to the first historical storm in new england the great colonial hurricane of 1635 evidence of near modern and mid holocene storm events along saco bay includes washover units and marsh ridges washovers interfinger with saltmarsh peat that ranges in age from 4 5 ka bp to modern the presence of isolated sandy ridges behind existing and former tidal inlets reflects overtopping of marshes and high intertidal mudflats during major storms radiocarbon ages indicate that this process took place at different locations along the saco bay barrier complex from 3 to 1 ka bp d 2004 elsevier b v all rights reserved

optical dating of sediments a new method for dating sediments is proposed which determines the time since the sediment was last exposed to sunlight an argon ion laser is used to excite electrons from thermally stable light sensitive traps and the subsequent luminescence used as a measure of the past radiation dose two sample sequences spanning the periods 0 700 kyr and 0 6 kyr show steadily increasing luminescence with age an age of 62 8 kyr is obtained for a silt radiocarbon dated at 58 8 0 3 kyr problems were found with two much younger samples

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