microbe clay interactions as a mechanism for the preservation of organic matter and trace metal biosignatures in black shales abstract organic rich fine grained sedimentary rocks such as black shales are important geochemical archives providing information on the evolution of seawater composition and biological activity over the past 3 billion years while biological productivity and sedimentation rates greatly affect the organic matter content in these rocks mechanisms linking these two processes remain poorly resolved here we examine the interactions of clay minerals with the marine planktonic cyanobacterium synechococcus sp pcc 7002 we suggest that clays settling through the water column could influence carbon and trace metal burial in three ways 1 the interaction of reactive clay surfaces with the bacterial cells increases organic matter deposition via mass increase in a seawater growth medium by several orders of magnitude 2 reactive bacterial cells become completely encased within a clay shroud enhancing the preservation potential of this organic matter and 3 the trace metal content of the biomass buried along with metals sorbed to the clay particles contributes to the trace metal concentrations of the black shale precursor sediments significantly our findings imply that the chemical composition of ancient organic rich fine grained deposits are not only archives of ancient seawater composition and redox state but they also provide a record of the degree of biological activity in the water column through geological time

sedimentary facies and holocene depositional processes of laura island majuro atoll article i nfo article history the depositional processesthat formed lauraisland majuroatoll marshall islands were reconstructed basedon a facies analysis of island sediments and spine ratios and radiocarbon ages of foraminifera sedimentary facies were analyzed from trenches and drill cores excavated on the island and its adjacent reef flat depositional ages were obtained using benthic foraminifera calcarina whose spines had not been abraded the facies were classified into two types gravelly and sandy the initial sediments of these sites consisted of gravelly facies in the lower horizon and sandy facies in the upper horizon their ages were approximately 2000 cal bp and coincident with the onset of a 1 1 m decline in regional relative sea level which enabled deposition of the gravelly facies half of the sand fraction of the sediment was composed of larger benthic foraminifera the spine ratioshowedthat theirsupply source on the reef flatwaslocated oceansideof theisland the supplysource appears to have been caused by the relative sea level fall this indicates that the studied island was formed by a relative reduction in wave energy and enhanced foraminiferal supply both of which were triggered by the late holocene relative sea level fall

growth limiting size of atoll islets morphodynamics in nature several linear models have been proposed for islet evolution these models do not address the non linear processes contributing to islet evolution or account for feedback between islet morphology and the fluid dynamics leading to sediment sequestration the non linear sediment allocation model sam has also been proposed for atoll islet evolution the sam is a quantitative model of atoll islet development implemented assuming that there is morphodynamic feedback between islet topography and the fluid dynamics leading to sediment sequestration in islet sinks the sam requires measurements of islet volume to recover parameters in the model using a data inversion algorithm the sam was developed and tested using synthetic data in order to determine the effect of errors in the islet volume measurements on model parameters in this study the model parameters are estimated using radiocarbon dated samples from published field studies of islet development on atolls these calibration procedures involved reanalysis of the data using methods consistent with the morphodynamic principles of islet growth underlying the sam the results support a pattern of islet growth characterized by rapid lateral expansion followed by diminishing vertical accretion and shoreface rotation due to morphodynamic feedback

holocene raised beach ridges and sea ice pushed boulders on the kola peninsula northwest russia indicators of climatic change the primary aim of this paper is to describe and discuss the palaeoclimatic significance of mid to late holocene fields of raised beach ridges at matalaniemi and sea ice pushed boulders at kutovaya

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

lateglacial and holocene climatic changes in south eastern patagonia inferred from carbonate isotope records of laguna potrok aike argentina abstract first results of strontium calcium carbon and oxygen isotope analyses of bulk carbonates from a 106 m long sediment record of laguna potrok aike located in southern patagonia are presented morphological and isotopic investigations of m sized carbonate crystals in the sediment reveal an endogenic origin for the entire holocene during this time period the calcium carbonate record of laguna potrok aike turned out to be most likely ikaite derived as ikaite precipitation in nature has only been observed in a narrow temperature window between 0 and 7 c the respective carbonate oxygen isotope ratios serve as a proxy of hydrological variations rather than of palaeotemperatures we suggest that oxygen isotope ratios are sensitive to changes of the lake water balance induced by intensity variations of the southern hemisphere westerlies and discuss the role of this wind belt as a driver for climate change in southern south america in combination with other proxy records the evolution of westerly wind intensities is reconstructed our data suggest that weak shw prevailed during the lateglacial and the early holocene interrupted by an interval with strengthened westerlies between 13 4 and 11 3 ka cal bp wind strength increased at 9 2 ka cal bp and significantly intensified until 7 0 ka cal bp subsequently the wind intensity diminished and stabilised to conditions similar to present day after a period of reduced evaporation during the little ice age strontium isotopes 87 sr 86 sr ratio were identified as a potential lake level indicator and point to a lowering from overflow conditions during the glacial 17 ka cal bp to lowest lake levels around 8 ka cal bp thereafter the strontium isotope curve resembles the lake level curve which is stepwise rising until the little ice age the variability of the ca isotope composition of the sediment reflects changes in the ca budget of the lake indicating higher degrees of ca utilisation during the period with lowest lake level

the morphodynamics of beach ridge formation magilligan northern ireland abstract magilligan foreland is a holocene beach ridge plain comprising three principal sets of sand ridges sets i and ii are related to the mid holocene progradation of the plain while set iii represents recent deposition at the distal margin at present two types of beach ridge are being formed in both cases as part of the general recovery sequence following storm erosion of the dune cliffs mode i beach ridge development is associated with shore normal sediment transport under dissipative wave conditions these ridges form around the high water mark of spring tides through the migration of coalescence of swash bars within 30 to 55 days of a storm mode ii formation is more complex sediment initially stored in nearshore bars is moved alongshore causing bar elongation the bar moves into the intermediate and even reflective wave domains eventually narrowing of the bar leads to severance of a downdrift portion usually at or near the major drift pulse to the north west of the foreland normally this sediment starved remnant welds progressively onto the beach face in the direction of the dominant process gradient east to west but occasionally locally generated counteractive seas move sediment onshore employing the bar as a traverse conduit mode ii beach ridges emerge onto the upper beach around 90 150 days after a storm the beach ridges have distinctive structures depending on their mode of formation and both constitute important sources for dune building sand

holocene coastal dune formation in southern australia a case study abstract the 14 500 km long southern australian coast is exposed to high energy wave and wind regimes which have mobilized shelf derived sediments to produce extensive holocene shoreface deposits the 8000 km of sandy coast are backed by over 2000 km 2 of holocene dunes of varying degrees of stability in places dune deposition above present sea level accompanied the post glacial marine transgression commencing as early as 10 ka b p and has continued episodically to the present day the dunes are widespread in extent but vary in type size and evolution the oldest and often most extensive primary dune fields accompanied the post glacial marine transgression they occurred and in some places continue to form in areas of high wave and wind energy and abundant sand supply many of these systems exhausted their sediment supply by mid holocene and remain as stranded clifftop dunes where sand ramps were eroded or as eroding barriers secondary phases of dune activity occurred on moderate to high energy coasts following an initial period of post stillstand barrier progradation diminished sediment supply resulted in shoreline erosion and secondary dune formation the location size and evolution both of dunes types is largely controlled by the breaker wave regime which in turn influences the rate and volume of sediment supply beach morphodynamics and resulting aerodynamic boundary conditions and foredune erosion a study of dune formation along the 3700 km long south australian coast provides a basis for an overview of dune formation throughout southern australia

controlling factors of ca isotope fractionation in scleractinian corals evaluated by temperature ph and light controlled culture experiments abstract in this study the 44ca 40ca ratios of porites australiensis grown under three different culture experiments composed of temperature ph and light controlled culture experiments are measured the temperature dependent isotope fractionation of 0 02 c deduced from this study is similar to inorganic aragonite but the degree of isotope fractionation is about 0 4 offset in corals these observations agree with earlier results on different coral species suggesting ca isotope fractionation during ca transmembrane transport in corals while in cultured corals a significant temperature dependence of 44ca is observed the relationships between calcium isotope fractionation and ph as well as light intensity are negligible therefore variation of 44ca in porites corals is mainly controlled by temperature a combination of 44ca and sr ca of corals in temperature controlled experiments cannot be explained by rayleigh type fractionation directly from a fluid which is seawater like in terms of 44ca and sr ca through coral specific biomineralization processes overall mean 44ca of scleractinian corals including previous studies are different from biogenic aragonites secreted by sclerosponges and pteropods but are comparable with those of bivalves as well as calcitic coccolithophores and foraminifers these findings are important for better understanding biomineralization in corals and in order to constrain the ca isotopic composition of oceanic ca sinks in response to climate changes and associated with shifts of calcite and aragonite seas

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

theoretical constraints and chronological evidence of holocene coastal development in central and southern new south wales australia abstract holocene coastal evolution in new south wales has been interpreted essentially as the unfolding of the impact of marine transgression sea level on this coast supposedly reached its present height at 6 6 5 ka and varied

calcium isotope fractionation in ikaite and vaterite abstract we investigated the isotopic composition of calcium in the metastable calcium carbonate polymorphs vaterite and ikaite the synthetic vaterite precipitates show a smaller degree of ca isotope fractionation than calcite or aragonite at comparable temperatures and revealed no significant temperature sensitivity between 10 and 50 c ikaite the water bearing ca carbonate modification caco 3 6h 2 o was precipitated at 2 c in controlled laboratory experiments and in addition recovered from marine sediments and sea ice synthetic and natural ikaites show similar values of ca isotope fractionation in general ikaite is less depleted in heavy isotopes compared to calcite or aragonite at low temperatures the observed offset of vaterite and ikaite to calcite or aragonite precipitated at similar temperatures is presumably mainly related to differences in precipitation rates and regimes which seem however to be typical for the growth of these carbonate minerals small differences in ca isotope ratios of naturally formed ikaites from different locations seem to be related to different geochemical conditions in the respective sediment settings

origin of strontium and calcium in pedogenic needle fibre calcite nfc abstract strontium sr and calcium ca isotopic compositions and sr ca ratios have been analysed in different fractions of pedogenic needle fibre calcite nfc from the swiss jura mountains villiers neuch tel switzerland in order to determine their ca sources and to investigate the potential role of fungi in the origin of nfc 87sr 86sr ratios have been measured to trace the ca trapped within different pedogenic carbonate this ratio was compared for previously identified microscopic morphological groups of nfc the bulk soil fine earth

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

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 shoreline progradation and coastal evolution at guichen and rivoli bays southern australia prograded barrier systems record shoreline behaviour and palaeoenvironmental information the guichen bay holocene embayment fill succession in south australia has been subject to several prominent

holocene coral reef development under windward and leeward locations at ishigaki island ryukyu islands japan abstract coral reef growth is largely controlled by the wave energy associated with ocean swells and local winds this growth has responded to changes in wave conditions that evolved in concert with holocene sea level changes we analyzed holocene facies of the ibaruma and fukido reefs of ishigaki island southern ryukyu islands in the context of temporal and spatial changes in wave conditions by comparing present day coral assemblages and internal fossil reef facies four major coral assemblages that developed under different wave energy conditions were recognized six cores recorded a holocene reef sequence consisting of four sedimentary facies that differed in the relative volumes of four coral taxa acropora digitifera and acropora hyacinthus and lesser amounts of favia stelligera and montastrea curta holocene windward reef growth began at 7820 cal years bp after flooding of the pleistocene reef limestone surface the ensuing reef growth kept up with the rapid sea level rise a vertical growth rate of 7 5 m 1000 years during reef nucleation and early growth stages decreased to 3 5 m 1000 years during the main stage of reef framework development the uppermost part of the windward reef consisted of a very robust framework unlike the open framework of the leeward reef ages indicated that the uppermost leeward reef was ca 3000 years younger than the uppermost windward reef these variations in facies development and timing were caused by differences in local wind driven wave conditions

elucidating modern geochemical cycles at local regional and global scales using calcium isotopes abstract in earth s surface environment calcium ca is an important mobile metal that is actively and passively transported in solution and within organic and mineral phases being cycled and recycled during various biogeochemical processes with the development of modern mass spectrometric techniques small variations in the stable and radiogenic isotopic compositions of ca can be measured revealing insight in these complex biogeochemical cycles and tracing and quantifying components across a range of spatial and temporal scales similar to other more routine isotope systems more than three decades of work reveal systematic variations in the partitioning of ca isotopes due to both abiotic and biological processes an overview of processes that fractionate ca isotopes at local regional and global scales is outlined here we present detailed examples of instances in which ca isotopes have provided unique insight into the functioning of earth surface processes and the cycling of ca at multiple scales future studies should target questions for which ca isotopic analysis provide unique insight and when combined with other isotope and trace element multi proxy studies better constrain the system of interest at the same time we challenge the scientific community to explore new frontiers including polar regions and other extreme environments

shoreface sand supply to beaches the possibility of sand supply from the shoreface to beaches was evaluated based on a variety of methods involving field data and modeling results obtained from five coasts on three continents representing a wide range of coastal environments the field data include wave current measurements historical seabed soundings and geological surveys cross shore transport estimates from modeling on the annual time scale were compared against scaled down inferences from the seabed change and geological data the results are all consistent with there being net onshore transport over the long term from the lower shoreface to beaches in each of the environments these environments typify settings that occur commonly probably predominantly along the world s coasts so net shoreface sand supply to beaches may be a widespread and common but little appreciated factor in coastal stability the effect of this net supply is to offset other factors causing shoreline recession such as positive gradients in littoral transport moreover shoreline progradation occurs if sand supply from the shoreface dominates over littoral sediment losses implications are clearly significant for coastal engineering and coastal management despite the processes not being immediately apparent long term shoreface sand supply to beaches is masked by more rapid cyclical changes rates of shoreface sand supply to beaches indicated from various lines of evidence are typically on the order of 10 0 m 3 a 1 per meter of shoreline this volume corresponds to a lowering of the shoreface by only a few grain diameters per year

calcium isotope fractionation upon experimental apatite formation abstract carbonated hydroxy apatite ca10 b nh4 k na 2b po4 6 y co3 2x 3 2 y oh 2 2x chap was synthesized in batch type experiments by mixing of calcium ca and phosphate bearing aqueous solutions and the transformation of calcite powder in aqueous solution between 11 and 65 c compositional changes of the mother solution and solid phase products were followed by powder xrd scanning electron microscopy sem edx raman spectroscopy and elemental analysis it was found that the transformation at ph values between 7 5 and 7 9 occurs via the dissolution of calcite followed by the precipitation of chap in the mixing approach crystallization of chap took place via precipitation of metastable brushite cah po4 2h2o as precursor phase that was further transformed into apatite calcium isotope fractionation led to an enrichment of the light isotope by about 0 5 to 1 1 in the solid chap compared to the aqueous solution consistently in all experimental approaches essentially independent of temperature in some experiments metastable brushite formed prior to transformation to chap and showed a reduced fractionation compared to the chap the observed ca isotope fractionation into the chap lattice resembles that of natural phosphorites and lies within the range of recently published experiments

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

influence of wave energy on holocene coral reef development an example from ishigaki island ryukyu islands japan abstract wave energy induced by ocean swell and local winds is an important factor controlling the coral reef development here we compare and contrast facies ages and accretion rates of reefs that developed independently along windward and leeward margins of the same island as both reefs face the open ocean swells provide a background of low to medium energy condition with additional energy along windward margins due to prevailing winds this similarity of the wave energy regimes medium to high energy produced a similar framework facies that was constructed by robust branching acropora however much greater lateral accretion rates were observed in the high energy reef than in the medium energy reef also coral cobble facies were only found in the medium energy reef indicating that the reef framework was more susceptible to storm breakage than that in the high energy reef these differences are attributable to the differing biological and ecological responses of corals to wave energy and water motion

hurricane induced sediment transport in open shelf tropical systems an example from st croix u s virgin islands hurricane hugo passed directly over st croix on 17 september 1989 sustained winds in excess of 110 knots gusts to 165 knots and waves 6 7 m in height accompanied the storm along the north coast wave height was lower ca 3 4 m due to the leeward position of the shelf in the deeper reefs at cane bay and salt river damage was confined primarily to the soft bodied benthic community e g sponges gorgonians coral damage was much less severe largely because of the buffering effects of the water column the greatest change observed after the storm was wholesale flushing of sand from shelf edge areas in salt river submarine canyon a minimum of 2 million kg of sediment were flushed into deeper water the transport rate associated with the storm was eleven orders of magnitude above that measured during fair weather and the volume of sediment that was removed from the canyon equalled roughly a century of normal sediment accumulation at cane bay 336 000 kg of sediment were flushed from a single channel with similar amounts removed from adjacent breaks in the shelf edge reef a current meter in salt river submarine canyon provided information on the timing and intensity of the oceanographic processes related to hurricane hugo as the storm approached waves piled water against the shoreface and in salt river bay as the storm passed over st croix the change in wind direction followed by a decrease in wave height triggered a release of water trapped in the bay and along the adjacent shoreline by waves earlier in the storm for a period of 4 6 hours net down canyon currents reaching 2 m s and oscillatory flows up to 4 m s occurred along the base of the western canyon wall removing up to 2 m of sand similar events were likely responsible for the wholesale removal of sand in eastern cane bay the paradoxical concurrence of wholesale sediment transport and low level reef damage is related to the protection from waves but not wind afforded by the north coast of st croix facing away from the direction of storm approach these observations and measurements provide our first opportunity to relate sediment export in such a high energy event to the physical processes that were responsible calculations based on post hugo measurements are in agreement with an earlier sediment budget for salt river canyon sediment export in cane bay exceeded the volume similarly predicted because such events are probably common on all exposed carbonate shelf margins storms like hurricane hugo are among the most important factors in the cycling of sediment through exposed open marine environments both now and in the geologic past the patterns of reef damage and sediment transport are much more complicated than previously envisioned and more thoughtful consideration of their variability and the processes responsible is essential to an understanding of the signature that will be left by major storms

relationship between species diversity and reef growth in the holocene at ishigaki island pacific ocean abstract coral reefs are influenced by global and local factors and living corals are currently faced with a potential loss of species diversity knowledge of the relationship between species diversity and reef growth during the holocene is important in terms of accurately reconstructing natural conditions prior to recent disturbances e g human impact pollution and over harvesting and in predicting future scenarios e g abrupt sea level rise coastal change and economic services this study seeks to characterize the holocene and present day reef at ishigaki island in the ryukyu islands focusing on spatial and temporal variations in the relationship between species diversity and reef growth the analysis is based on a drilling core obtained for the holocene reefs and quantitative species diversity data shannon and weaver s diversity index h obtained for the present day reef h was calculated for four coral communities surveyed at the ibaruma and fukido reefs the holocene sequence was dominated by the corymbose coral community e g acropora digitifera a hyacinthus goniastrea retiformis and platygyra ryukyuensis yielding an h value of 1 6 the encrusting coral community e g echinopora lamellose and pachyseris rugosa showed the highest diversity at the reef h 2 2 however this community was not one of the main reef builders during the holocene the massive coral community e g porites lutea and favites chinensis showed the lowest diversity h 0 6 it also made a minor contribution to reef building this community appeared in a shallow lagoon once sea level had stabilized the arborescent coral community e g a formosa and a nobilis was one of the main reef builders although yielding an h value of much less than 1 0 species diversity is not a prerequisite in terms of holocene reef growth thus a few species e g a digitifera a hyacinthus a formosa a nobilis g retiformis and p ryukyuensis from two main reef building communities are important for reef growth these corals that act as reefs are characterized by high growth rates having an upward reef growth rate of 2 12 m kyr 1 in the indo pacific during the holocene

ca isotope constraints on chemical weathering processes evidence from headwater in the changjiang river china abstract this study aims to clarify the relationship between chemical weathering of rocks and the carbon budget of rivers and better understand the weathering mechanisms of plateau watersheds we chose to study the jinsha river which originates from the tibetan plateau and also is in the upper reaches of the changjiang river analysis of hydrochemistry radiogenic strontium isotope and stable calcium isotopes were conducted of the jinsha river water samples which were collected along its mainstream and main tributaries in the summer the results show that the water chemistry of the mainstream waters is dominated by evaporite weathering which have low 87sr 86sr values 0 7098 0 7108 and wide range of sr contents 2 70 9 35 mol l in contrast tributaries of the jinsha river have higher 87sr 86sr 0 7090 0 7157 and lower sr contents 1 mol l moreover the ca isotopic compositions in the mainstream 0 87 1 11 are heavier than the tributaries 0 68 0 88 and could not be fully explained by the conventional mixing of different sources we suggest that secondary carbonate precipitation fractionates ca isotopes in the jinsha river and fractionation factors are between 0 99935 and 0 99963 at least 66 of ca was removed in the mainstream of the jinsha river through secondary mineral precipitation and the average value is 35 in the tributaries the results highlight that evaporite weathering results in more carbonate precipitation influencing ca transportation and cycling in the riverine system constrained by stable ca isotopic compositions and water chemistry

late quaternary evolution of coastal sand barriers port stephens myall lakes area central new south wales australia abstract the geomorphic and stratigraphic history of six coastal embayments has been studied in the vicinity of newcastle new south wales n s w australia in order to determine modes of deposition and the degree to which marine and estuarine deposits can be correlated and dated each embayment possesses its own distinctive suite of landforms ranging from those dominated by coastal dunes to those in which beach ridges occur in four of the bays dual sand barriers comprising an inner barrier and an outer barrier provide the framework for correlation between embayments six stages are recognized in the deposition of late quaternary sediments in this area i pre last interglacial involving accumulation of separate composite units consisting of estuarine clays and transgressive dune complexes ii last interglacial stage during which inner barriers were formed iii last glacial reworking of barrier and dune sands by westerly winds iv postglacial marine transgression during which the outer barriers were initiated v mid holocene stage following cessation of sea level rise ca 6000 6500 yr b p on this coast and involving progradation of outer barriers in some embayments and vi late holocene episodic eolian reworking of dune complexes and outer barriers the relatively high wave and wind energy as well as the tectonic setting of the central n s w coast results in somewhat different geomorphic histories from barrier island coasts in north america and europe

holocene sea level change and evolution of a mixed coral reef and mangrove system at iriomote island southwest japan abstract exposed fossil microatolls and core samples from a coral reef and a mangrove forest at the yutsun river mouth iriomote island southwest japan reveal the internal structure and temporal changes in the sedimentary processes of a mixed reef mangrove system evidence from the core samples and fossil microatolls suggests sea level reached its present position before 5100 cal yr b p and a relative sea level highstand of 1 1 1 2 m above the present sea level occurred from 5100 to 3600 cal yr b p this was followed by a gradual fall in relative sea level the tectonically corrected sea level curve indicates a stable sea level after 5100 cal yr bp with a sea level highstand of up to 0 4 m between 5100 and 3600 cal yr b p a nearshore reef dominated by massive porites and arborescent acropora initially developed at 6500 3900 cal yr b p reef development was potentially terminated by relative sea level fall and sediment discharge from the yutsun river that affected the backreef environment an offshore coral reef reached present day sea level by 1000 cal yr b p forming a wave break that enabled the foundation of mangrove forest on the fringing reef after 1000 cal yr b p the reef development was significantly delayed compared with other coral reefs in the region with similar medium to high energy conditions but it provided a calm environment in the backreef area that allowed the development of mangroves these features demonstrate the chronology and causal relationship between coral reef and mangrove development under the influence of holocene sea level change and river discharge

controls on calcium isotope fractionation in sedimentary porewaters abstract the calcium isotopic composition of porewaters and authigenic carbonates in the anoxic sediments of a convergent continental margin drilled during ocean drilling program odp provides first insight into the different processes that control ca geochemistry in clastic marine organic rich sedimentary environments in 4 sites drilled during leg 204 at hydrate ridge cascadia margin offshore oregon usa sulfate is consumed during anaerobic oxidation of methane and of organic matter via sulfate reduction within the upper meters of the sedimentary section these reactions promote the precipitation of authigenic carbonates through the generation of bicarbonate which is reflected in a pronounced decrease in calcium concentration although ca isotope fractionation is observed during carbonate precipitation ca concentration in the pore fluids from odp leg 204 is decoupled from ca isotopy which seems to be mainly controlled by the release of light ca isotopes that completely overprint the carbonate formation effect different processes such as the release of organically bound ca ion exchange and ion pair formation may be responsible for the released light ca deeper within the sedimentary section additional processes such as ash alteration influence the ca isotopic composition of the porewater two sites drilled into the deeper core of the accretionary prism reveal the nature of fluids which have reacted with the oceanic basement these deep fluids are characterized by relatively high ca concentrations and low 44 40ca ratios

origin of beach ridges and swales abstract sandy beach ridges occur in four main categories 1 swash built 2 settling lag 3 eolian 4 storm surge ridges in the first two classes are geometrically regular only a few tens of centimeters above adjacent swales and commonly in ridge sets and systems tens to hundreds of ridges each individual sets of 5 25 ridges tend to stand 0 5 m to 2 m above or below adjacent sets ridges in the third and fourth classes do not have these characteristics do not occur in sets and are generally not suitable for detailed historical studies no one of these ridges is the same as the storm built berm which is almost never preserved swash built sandy beach ridges have diagnostic 1 map spacing 2 accretion rate 3 periodicity 4 crossbedding and 5 granulometry the last two indicate fair weather waves on a sandy beach in contrast with settlinglag ridges postma style which have the same external geometry but which were deposited without important wave work and in contrast with storm built berms generally seen on eroding coasts but rarely or never in beach ridge plains the grain size kurtosis of beach sand is an excellent index to near shore wave energy density changes in kurtosis at ridge set boundaries mark changes in long term wave energy density hence in sea level the latter can be deduced also from set height differences and from spacing differences periodicity is typically 30 60 years map spacing 25 50 m and accretion rate fairly close to 1 m yr a few ridge sets with intervals of 3 7 10 12 or 18 19 years have smaller spacings this is not what can be done if each ridge is built by one storm if each ridge had been built by one storm wide beach ridge plains like one in denmark dating from about 11 700 yr b p would have been formed in the last 30 50 years at accretion rates of hundreds of meters per year instead each swash type sandy beach ridge was made by a sea level rise and fall couplet amplitude 5 30 cm the swale marks the lower position this mechanism reflects the fact that the transverse profile from beach to sea is gently concave upward with maximum curvature close to shore this is a shape which is out of adjustment with the shoaling wave system shortly after a small sea level change settling lag ridges were built without waves hence the ridge and swale sequence in this case cannot be attributed to waves either fair weather or storm these ridges show the same historical pattern as do swash built ridges this fact suggests that both were controlled by the same mechanism sea level change

wave climate sand budget and shoreline alignment evolution of the iluka woody bay sand barrier northern new south wales australia since 3000 yr bp abstract multi centennial fluctuations in the northern new south wales nsw coastline alignment are interpreted from a detailed reconstruction of the morphological and depositional evolution of the iluka to woody bay barrier during the late holocene the regional coastline is aligned obliquely to the south east inner shelf modal wave direction and hence sediment is transported obliquely on the shoreface with a net northward movement on centennial to millennial time scales the coastline is shown to have responded to fluctuations in mean wave direction longshore gradients in sand transport and headland sand bypassing processes overall barrier progradation has been punctuated by episodes of shoreline recession and realignment throughout the late holocene a prolonged shoreline recessional phase occurred at 1500 yr bp in response to a rotation in modal wave direction from more southerly towards east south easterly subsequent to this realignment renewed shoreline progradation occurred along the east aspect coastline after 1400 yr bp whilst the north east aspect coastline remained in a receded alignment until after 1000 yr bp when renewed progradation occurred progradation rates increased throughout the past millennium driven by changes to the alongshore gradient in sand transport under an implied shift to a more southerly and energetic modal wave climate in the past 50 yrs the north east aspect shoreline has experienced a rapid recessional trend which is associated with a shift in modal wave climate to a more east southeasterly direction and a reduction in headland sand bypassing the average sand supply rate to the iluka to woody head section of the northern nsw shoreline is 4 1 m3 m yr since 3000 yr bp

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

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

calcium isotopes in a proglacial weathering environment damma glacier switzerland the biogeochemical cycling and isotopic fractionation of calcium during the initial stages of weathering were investigated in an alpine soil chronosequence damma glacier switzerland this site has a homogeneous silicate lithology and minimal biological impacts due to sparse vegetation cover calcium isotopic compositions obtained by tims using a 43ca 46ca double spike were measured in the main ca pools during this very early stage of weathering the young soils which have formed 44 42ca 0 44 44 42ca 0 44 were indistinguishable to the rocks from which they were derived 44 42ca 0 44 44 42ca 0 44 and stream water 44 42ca 0 48 44 42ca 0 48 was also within error of the average rock this lack of variation indicates that the dissolution of the bulk silicate rock does not strongly fractionate ca isotopes the only ca pool which was strongly fractionated from bulk rock was vegetation which exhibited an enrichment of light ca isotopes significant ca isotope fractionation between bulk rock and the dissolved flux of ca is likely to only occur where the ca biogeochemical cycle is dominated by secondary processes such as biological cycling adsorption and secondary mineral precipitation

shallowing upwards sedimentation in a coral reef lagoon great barrier reef of australia abstract sediments in the 5 25 m deep lagoon of davies reef a typical mid shelf reef in the central great barrier reef are described based on data gleaned from 19 soft sediment cores 75 mm diameter up to 7 5 m penetration 22 surface sediment samples and air lift surveys the holocene sediment pile which averages 5 10 m thickness is entirely skeletal in origin and has a very poorly sorted coral gravel rich base which grades up into poorly sorted muddy sands with infaunal molluscan gravel these muddy sands mainly derived from the reef rim as opposed to being produced in situ on the lagoon floor have been intensely bioturbated by callianassid shrimps leaving the infaunal molluscan gravel patchily distributed and the bivalves disarticulated and preferentially oriented sub hori ontally concave up there are no vestiges of primary depositional sedimentary structures such as bedding or cross bedding radiocarbon dating suggests that significant accumulation of muddy sand in the center of the lagoon did not begin until about 2 500 3 000 yr bp and that sediment accumulation rates have increased through time from an average of 1 4 mm yr between 2 400 and 640 yr bp to 3 4 mm yr over the past 640 years interpreting these data the coral gravel rich base to the sediment pile represents a period of prolific coral growth across the top of davies reef platform following flooding by the holocene transgression but before the outer reef rim caught up with sea level to form a lagoon when the rim did reach sea level about 3 000 4 000 yr bp it started to shed large qua tities of mud and sand grade sediment into the center of the reef platform and this combined with decreased water circulation led to the demise of coral growth in the newly formed lagoon as the area of reef rim at sea level increased so too did the supply of sediment to the lagoon which explains the observed increase in sediment accumulation rate through time using previously published data to aid speculation into the future development of the lagoon a shallowing upwards model for reef lagoon sedimentation is developed in this model a complete sequence consists of a fining upwards base reflecting the gradation from coral gravel up into bioturbated muddy sands and a coarsening upwards top reflecting a gradation from bioturbated muddy sands up into a zone of shallow subtidal co al rubble and patch reefs then inter and supratidal windward storm shingle ramparts and leeward sand cays

the stranded beach dune sequence of south east south australia a test of thermoluminescence dating 0 800 ka the remarkable sequence of stranded beach dunes in south east south australia deposited during the past 800 ka has provided us with a rare set of samples for testing thermoluminescence sediment dating methods here we report thermoluminescence ages obtained from quartz separated from the dunes and compare them with accepted ages for the high sea levels responsible for the dunes the independent ages of the dunes were obtained from earlier work by schwebel which has been extended and refined by modelling the dune formation using sea level variations derived from the oceanic 18o record the work is unusual in extending thermoluminescence dating to an 800 ka sequence with modest geological control of the age the agreement between thermoluminescence and geological ages is satisfactory for eight dunes with ages in the range 120 800 ka quartz is not usually thought to be useful for thermoluminescence dating in this time span two factors contribute to our success the first is that the dose rates are low about 0 5 gy ka 1 or one quarter of that typical of sediments the second is that the thermoluminescence vs dose response continues to rise monotonically above the saturation region at doses above 300 gy

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

contradicting barrier reef relationships for darwin s evolution of reef types the darwinian progressive subsidence model for the evolution of fringing reefs barrier reefs and atolls has been generally accepted following the indisputable proof of subsidence provided by drilling results in the pacific nonetheless there are data that do not fit the expectations of the model such as the similar lagoon depths of barrier reefs and atolls as opposed to the subsidence theory s implicit prediction that atolls should have significantly greater depths in contrast a great deal of evidence supports the influence of meteoric solution on barrier reef morphology for example the maximum lagoon depth of 56 modern barrier reefs is statistically correlated with the lagoon catchment area for modern annual rainfall these modern rainfall patterns would seem to be a reasonable proxy for relative geographic differences in glacial lowstand rainfall even though the absolute amounts of such rainfall are unknown the correlation therefore suggests the importance of pleistocene subaerial solution in contributing to barrier reef morphology further support for antecedent influence occurs in the form of barrier reef passes in which the depth of the reef pass is correlated with onshore drainage volumes on a larger scale the cook island of mangaia provides evidence that solution can produce barrier reef morphology independent of reef development in contrast there are no examples of the subsidence predicted lagoon transition of fringing reefs to barrier reefs to atolls moreover the common occurrence of fringing reefs within barrier reefs negates subsidence as a causal factor in their presumed progressive evolutionary development consequently the evidence to date suggests that a solution morphology template has been accentuated by reef construction to produce the diagnostic barrier reef morphology we see today the importance of subsidence would seem to be in accounting for the overall thickness of the resulting carbonate caps of oceanic examples and in contributing to lagoon depth variation among the larger continental entities

the origin of centennial to millennial scale chronological gaps in storm emplaced beach ridge plains recent studies of tropical cyclone surge and wave emplaced beach ridge plains have shown that these sequences often contain centennial to millennial scale gaps in their chronologies two explanations for the gaps exist they are due to erosion or alternatively a cessation or substantial slowing of depositional processes suggestive of a quieter phase in intense storm activity differentiating between the two is important for uncovering reliable long term storm histories from these sequences we use landform morphology sediment texture and luminescence chronology to determine the origin of substantial chronological gaps in a plain containing more than 100 shore parallel ridges composed of fine grained sand located in northeast australia we identify and describe the characteristics associated with both erosional and non erosional gaps the erosional gaps are associated with changes in orientation between ridge sets and often a high ridge with hummocky topography that appears to have been disturbed by aeolian activity river floods likely caused the partial erosion of ridge sets non erosional gaps do not display these morphological characteristics and are likely associated with quiescence in severe tropical cyclone activity these geomorphic and chronological signatures can be used to identify different sorts of gaps in other ridge plains and are an important tool in the reconstruction of long term storm histories from these coastal landforms the data also suggests that fine grained ridges can like their coarse grained counterparts be predominantly deposited by storm waves and surge and their texture need not necessarily be indicative of the processes responsible for ridge development

holocene hydrologic variability in temperate southeastern australia an example from lake george new south wales lake george is one of the largest freshwater lakes in australia when full and provides one of the most complete records of quaternary sedimentation in the southeastern part of the continent the lake is currently ephemeral but sediments within the basin preserve evidence of multiple permanent and dry lake conditions in the past we present an optically stimulated luminescence osl chronology of recent lake shoreline sediments in order to reconstruct holocene hydrologic variability at lake george providing past climatic context for the presently ephemeral lake conditions the osl chronology indicates three distinct periods of permanent lake conditions up to 15 18 m depth over the holocene period at approximately 10 8 6 2 4 and 0 7 0 3 ka with lower lake levels occurring in between those events there appears to be a trend towards lake regression over this period despite relatively recent high lake levels the chronology is broadly synchronous with comparable records of holocene climatic variability across southeastern australia we also investigate the intrinsic luminescence characteristics of different sediment types as diagnostic tools but these appear not to be appropriate in this context or form

calcium isotopes in deep time potential and limitations abstract calcium is an essential element in the biogeochemical cycles that regulate the long term climate state of earth the removal of co2 from the ocean atmosphere system is controlled by the burial of carbonate sediments caco3 ultimately linking the global calcium and carbon cycles this fundamental link has driven the development of the stable calcium isotope proxy with application to both ancient skeletal and non skeletal bulk carbonate sediments calcium isotope ratios 44 40ca have been used to track long term changes in seawater chemistry e g aragonite vs calcite seas and to elucidate short term climatic perturbations associated with mass extinction events however developments in the calcium isotope proxy have shown that 44 40ca values in carbonate minerals also are sensitive to changes in precipitation rates mineralogy and diagenesis thereby complicating the application of the proxy to the reconstruction of global cycles first inorganic carbonate precipitation experiments have demonstrated that carbonate 44 40ca values are sensitive to precipitation rates with higher rates generally leading to larger fractionation second 44 40ca values are sensitive to carbonate mineralogy with inorganic aragonite and calcite being on average 1 5 and 0 9 depleted relative to contemporaneous seawater respectively the effects of both changes in carbonate mineralogy and precipitation rates affect primary and secondary minerals but are particularly pronounced during carbonate diagenesis where relatively slow rates of recrystallization and neomorphism can lead to significant changes in bulk sediment 44 40ca values third changes in faunal composition expressed in skeletal fossil archives can lead to large changes in carbonate 44 40ca values that are decoupled from changes in global cycles nevertheless when these factors are appropriately considered the application of calcium isotopes in ancient carbonate sediments becomes a powerful tool for understanding biogeochemical processes that operate over many scales from diagenetic changes within the sediment pore space to regional changes across ancient carbonate platforms and to global changes in seawater chemistry through time importantly the processes that contribute to variability in carbonate 44 40ca values are likely to impact other carbonate bound proxies highlighting the potential for calcium isotopes as a tool to better understand the variability of other isotope systems

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

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

sulfate dependent anaerobic oxidation of methane at a highly dynamic bubbling site in the eastern sea of marmara cinarcik basin abstract during the marsitecruise expedition in november 2014 on board the rv pourquoi pas multidisciplinary sampling was carried out with the rov victor 6000 in order to investigate biogeochemical processes taking place at cold seep environments in the sea of marmara pore water bottom water sediment and authigenic carbonate samples were collected from two short push cores mrs dv5 pc04 8 cm mrs dv5 pc01 12 5 cm at an active methane bubbling site in the southeastern part of the cinarcik basin sulfate sulfur and oxygen isotope data as well as sulfide isotope data indicate that sulfate dependent anaerobic oxidation of methane is the dominant process in the sediments this is confirmed by archaeal lipids diagnostic for anaerobic methane oxidizers detected with strong 13c depletions the available data even allows to distinguish the dominant aom assemblages specific lipid patterns are consistent with a dominance of anme 2 archaea within the microbial community abundant authigenic carbonates mostly aragonite found at all depths show a narrow range in 13c values between 27 69 and 33 40 the carbon isotopic composition of the dissolved inorganic carbon as well as strontium and calcium isotopes confirm that the current reaction zone sulfate methane transition zone starts at the bottom of the core all shallower carbonates are witnesses of paleo seepage activity u th dating of four pure aragonite samples show the short time span that is preserved in core mrs dv5 pc01 235 60 yr b p two major earthquakes of 1766 ce and 1754 ce in the cinarcik basin might potentially have triggered the increased seepage of methane at this location

multi isotope approach δ44 40ca δ88 86sr and 87sr 86sr provides insights into rhizolith formation mechanisms in terrestrial sediments of nussloch germany abstract carbonates in loess paleosol sequences are considered as a valuable paleoenvironmental proxy for climate change during the quaternary period in this study we propose a new dataset of 44 40ca 88 86sr and 87sr 86sr to understand the formation of rhizoliths roots encrusted with caco3 within these kinds of sequences from nussloch region germany our results indicate that the leached fractions of rhizoliths sampled at 3 25 m 6 65 m and 8 45 m depths and leached with hcl have lower 44 40ca and 88 86sr and higher 87sr 86sr isotopic values than the leached fractions of rhizosphere and root free loess of the same stratigraphic levels this suggests different mechanisms of carbonate formation and different sources of sr and ca a three steps model of formation of rhizoliths from nussloch has been proposed first of all the roots grow in an existent stratigraphic level and the biological activity associated with roots allows for the dissolution of carbonate and non carbonate minerals a part of the available ca and sr is taken up by roots which absorb preferentially the light isotopes e g 40ca and 86sr a higher rate of water absorption by roots than nutrients in association with co2 released by biological respiration allows to reach supersaturation with respect to caco3 the precipitation of rhizolith carbonate selects preferentially the light isotopes e g 40ca and 86sr leading to lower 44 40ca and 88 86sr isotope values than the ones recorded on the closest rhizosphere and loess the higher 87sr 86sr signatures of rhizolith carbonates which is not modified by root uptake or by precipitation processes is the result of a mixture between 87sr 86sr signatures of carbonate and non carbonate minerals digested around the roots nevertheless grey zones remain in this main hypothesis about the very high contribution of residue materials to the isotopic signatures of rhizoliths in this light other mechanisms of downward transfer of ca and sr from upper stratigraphic level that could imprint the leached fractions of rhizoliths have been discussed

the stable calcium isotopic composition of rivers draining basaltic catchments in iceland calcium isotopic compositions 44 42ca were measured in icelandic rivers draining a range of catchment types the 44 42ca values of the rivers ranged from 0 45 to 0 67 which in all cases was higher than the 44 42ca value of basaltic rock standards 0 42 0 03 a single explanation was unable to satisfactorily explain the 44 42ca values of all rivers rather it was found that the rivers formed three distinct groups based on the extent of glacial coverage in each catchment the ca isotopic composition of rivers draining catchments with less than 10 glacial cover could be explained by the mixing of water sources basalt derived solutes meltwater taken to represent meteorological precipitation inputs and hydrothermal water however fractionation of 44 42ca in these catchments cannot unequivocally be ruled out in catchments with greater than 22 glacial cover ca isotopic compositions could not be explained by a mixture of water sources and instead reflected a fractionation process most likely the precipitation of ca bearing secondary minerals or the adsorption ion exchange of ca onto mineral surfaces the fractionation factor for this process was calculated to be 0 9999 the third group of rivers with partially glaciated 10 21 catchments grouped with glaciated catchments with respect to their sr geochemistry and with non glaciated catchments with respect to their ca geochemistry the difference in the controls of ca isotope fractionation between glaciated and unglaciated catchments was attributed to different weathering regimes

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

emplacement and movement of boulders by known storm waves field evidence from the okinawa islands japan abstract field observations from previous studies of boulder movements were compiled to augment our own work on boulders that have been displaced by storm waves during recent typhoon events in the okinawa islands japan to elucidate the ability of storm waves to move boulders our observations reveal that recent storm waves displaced by sliding and overturning 100 ton boulders emplacing them on the reef or high cliff tops and that storm waves might also be capable of displacing 200 ton boulders on the reef the weights of storm wave boulders at the okinawa islands are of comparable order to those boulders displaced by historical tsunami origins consequently boulder weight alone is an inappropriate parameter to discriminate between tsunami or storm wave processes however these heavy storm wave boulders are close to the reef and cliff edges while tsunami boulders can be deposited much further inland hence horizontal displacement distance of boulders could be a useful parameter to discriminate boulders deposited by the tsunami and storm waves on the wide fringing reef the storm wave boulders were characteristically concentrated on the southeastern pacific ocean sides of each island but large boulders are rarely found on the northwestern east china sea side this is probably because the storm wave intensities are generally stronger at the southeastern side than at the northwestern side although differences of reef strength and initial condition of boulders should also be taken into account consideration of the high frequency of typhoons at the area suggests that effects of the storm waves and the consequent displacement of boulders on the reef might have contributed to the formation of the reef moat framework that typifies the okinawa islands especially if the moat is located within the transport limit of the storm wave boulders approximately 300 m from the reef edge at the islands

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

revisiting late holocene sea level change from the gilbert islands kiribati west central pacific ocean new coral microatoll data allow presenting an updated late holocene sea level curve for the gilbert islands of kiribati examination of build up elevation and spatial distribution of microatolls along with radiocarbon age data from coral samples suggest an approximately 1 m sea level high stand possibly lasting from 3500 to 1900 cal yr bp our sea level curve which is similar to the one reported from the marshall islands is a baseline to reconstruct the evolution of reef flats and reef islands in addition it provides important contextual data to infer human settlement on islands in the west central pacific

geochronology and evolution of a complex barrier younghusband peninsula south australia abstract this study examines the southeastern end of the younghusband peninsula in south australia at a location called the granites in order to gain a better understanding of the processes of formation of the foredune ridge system and to investigate the drivers that controlled its progradational development during the holocene our findings are based on a morphological analysis a ground penetrating radar survey and 14c and osl dating the younghusband peninsula at the granites was formed by an initial aggradational phase resulting in a single complex foredune ridge and which ended around 4 3 ka and by a regressive progradational barrier phase 750 m wide that developed in the last 4 3 ka under very low rates of progradation 0 38 to 0 09 m yr the last part of this phase shows significant foredune ridge building in the last 1000 years or so barrier progradation via foredune ridge development is likely an effect driven by low wave energy that favored conditions for coastal stability and foredune formation paleontological and gpr data indicate a maximum sea level of 1 23 to 1 5 m respectively during initial barrier development the foredune ridge plain of the barrier experienced at least three phases of significant aeolian activity with ages centered at around 3 9 3 4 and 3 0 ka suggesting their occurrence at 500 to 400 year events computer modelling indicates that sediments for the progradational phase of the barrier were provided by the forced regression produced by a sea level fall over the past 4 3 ka the large foredune complex formed during the last phase of progradation could be the result of both the very low progradation rate of 0 09 m yr and periods of disturbance possibly related to enhanced storm activity

further thermoluminescence dates from the dune sequence in the southeast of south australia abstract our thermoluminescence dating technique has been applied to several new samples from the remarkable sequence of stranded beach dunes in southeast south australia that were formed during the past 800 ka we show that robe iii is probably 100 ka as suggested by schwebel and not 80 ka as we suggested earlier a sample from the west dairy dune is shown to belong to 18 o stage 7 in accordance with schwebel s original suggestion and not stage 5 as he suggested later a new west naracoorte sample yielded acceptable data and an age consistent with formation just after the brunhes matuyama magnetic reversal at 780 ka as required by palaeomagnetic measurements two more samples from the woakwine dune show that our reproducibility is consistent with our derived errors

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

the transient nature of the empty bucket model of reef sedimentation abstract the geometry of modern reefs has been likened to an empty bucket with the narrow reef rim comprising the container pail that encloses the water filled bucket while the analogy is valid the assumption that this constitutes a final geometry is not examples from the indian pacific and atlantic oceans individually and collectively demonstrate current filling of the lagoons by reef perimeter sand aprons since sea level only approximated its present position 3 to 6 ky ago it follows that the observed extent of modern highstand lagoon filling is minimal if the filling process was to continue unabated the result would be a flat topped bank but during the pleistocene low stands of sea level aborted the filling process extrapolating these relationships to the geologic record suggests that the empty bucket model of unfilled reef lagoon space is greatest during icehouse high frequency glacial fluctuations of sea level alternatively filled buckets in which cycle thickness approximates accommodation space are probably largely restricted to greenhouse time intervals the co occurrence of quaternary high amplitude frequency sea level changes with rapidly growing scleractinian corals probably enhanced the occurrence of empty bucket morphologies

anatomy of a modern coral reef flat a recorder of storms and uplift in the late holocene abstract cores from kabira reef ishigaki island southwest japan reveal the internal structure and temporal changes in sedimentary process of a complete coral reef flat the reef crest caught up with sea level at about 4000 yr bp since then it expanded oceanward and the reef pavement has grown landward the backreef structure is composed of bioclasts derived from the reef framework of all the bioclasts corals and coralline algae are most abundant coral fragments coarser than 3 0 o have dominated the backreef sediments since about 2000 yr bp benthic foraminiferal tests first occurred at about 4000 yr bp and their abundance increased significantly starting around 2000 yr bp shallowing of the reef crest is also indicated by the presence of the shallow water benthic foraminifera baculogypsina sphaerulata tests after 2000 yr bp the date 2000 yr bp is coincident with tectonic uplift at kabira reef kawana 1989 we consider this uplift to have caused a relative sea level fall that aided the deposition of coral fragments transported from the reef pavement by storms the relative sea level fall also caused subaerial exposure of the reef crest during low tides and the transition of reef building organisms from corals to shallow water species of benthic foraminifera resulting in a change noticeable in the constituents of backreef sediments the results of this study suggest that the coral reef flat and especially the backreef can be a faithful recorder of relative sea level changes

late holocene sea level change and reef island evolution in new caledonia abstract in new caledonia numerous cays are distributed on platform reefs in the southwest lagoon behind the barrier reef at mba island a vegetated sand cay in this area we examined holocene sea level change and reef development and evolution the late holocene sea level curve for the area was updated using newly found fossil microatolls component specific dating of foraminifera tests in the island sediment provided reliable ages of island formation mba island initially formed around 4500 cal yr b p when sea level was 1 1 m higher than at present the island formed on the leeward side of the platform reef where the base had been constructed of lagoon and reef derived sediment of the platform reef sea level fall since 2800 cal yr b p has likely caused reef flat emergence at low tide and created a suitable habitat for foraminifera such a transition in ecology due to sea level fall has been observed in other pacific reefs suggesting that the interaction between reef flat formation sediment production and sea level fall is one of the critical factors determining island development

spatial and temporal variability in the holocene sea level record of the south australian coastline abstract studies of past sea levels based on radiocarbon dated field samples suffer variously from compilation of information from disparate locations and the imprecise nature of the dated indicators geographic segregation and systematic elimination of poor samples from time depth data sets leads to improved interpretation of holocene sea level history an example is presented from southern australia where this is achieved through selection of higher resolution palaeoenvironmental indicators separation of transgressive from regressive populations and geographic regionalisation of data in southern australia fossil sea level indicators preserved in prograding coastal plain settings include seagrass sandflat mangrove samphire and chenier ridge organo sedimentary remains these provide sea level time depth data points with a variety of elevational and dating errors preserved organic remains at the transition from posidonia seagrass to intertidal sandflat environment and from sandflat to avicennia mangrove environment provide the most precise local data for tracing sea level change time depth plots of 233 dated sea level indicators from south australia generate a broad sea level envelope tracing the southern australian transgression from 10 000 to ca 6000 radiocarbon years bp followed by a more or less consistent level to the present finer details of sea level behaviour are only apparent after systematic selection separation and regionalisation of the data the data indicate a very rapid sea level rise in the early holocene at about 16 mm year reaching present levels at 6400 years bp this was followed by regionally variable regression and emergence of the land of 1 3 m a process that continues to the present the systematic increase from 1 to 3 m in the elevation of the 6400 year bp highstand with distance away from the shelf margin is consistent with a hydro isostatic origin for the emergence as predicted by geophysical models

modeling novel stable isotope ratios in the weathering zone when rock is converted to weathering products the involved processes can be fingerprinted using the stable isotope ratios of metals for example li mg ca fe sr and metalloids b si here we construct a framework for interpreting these novel stable isotope ratios quantitatively in the compartments of the weathering zone in a geomorphic context the approach is applicable to any novel stable isotope system and is based on a simple steady state mass balance model that represents the weathering zone from the scale of a soil column to that of entire continents our model is based on the assumption that the two main processes associated with isotope fractionation are formation of secondary precipitates such as clays and uptake of nutrients by plants the model results show that the isotope composition of a given element in the weathering zone compartments depends on 1 the ratio between the release flux to water through primary mineral dissolution and the erosion flux of isotopically fractionated solid material consisting of secondary precipitates and organic matter 2 the isotope fractionation factors associated with secondary mineral precipitation and uptake by plants a relationship is established between isotope ratios isotope fractionation factors and indexes for chemical weathering such as chemical depletion fractions cdf and elemental mass transfer coefficients derived from simple elemental concentration measurements from this relationship isotope fractionation factors can be calibrated from chemical and isotope data measured on field material furthermore we show how the ratio of solid export to dissolved export of a given element from the weathering system can be estimated from the comparison of the isotope composition between bedrock water and sediment this calculation can be applied to samples from soils from rivers and from the sedimentary record and does not require knowing the isotope fractionation factors involved in the reactions finally we apply the model to the oceanic li isotope record reconstructed from marine carbonate sediments in order to discuss changes in global geomorphic regimes through the cenozoic

cretaceous calcareous dinoflagellate cysts as recorder of δ44 40caseawater and paleo temperature using sr ca thermometry abstract we evaluate the potential of calcareous dinoflagellates as archives for sr ca based paleo temperature reconstructions and 44 40caseawater fluctuations on sediments from ocean drilling program expedition 113 hole 690c weddell sea southern ocean between 73 and 68 ma sr ca ratios of two cretaceous dinoflagellate species pirumella krasheninnikovii and orthopithonella globosa show a pronounced decrease consistent with a significant drop in sea surface temperature as reflected by the 18o of planktic foraminifers the apparent temperature sensitivity of the dinoflagellate cysts sr ca is 0 06 and 0 08 mmol mol c 1 using 18o derived paleo sea surface temperatures which is significant and large enough to resolve paleoenvironmental temperature changes at current analytical precision as the chemical composition of the cyst calcite appears to have a good preservation the sr ca of calcareous dinoflagellates has a potential to serve as paleo temperature proxy although the chemical composition of the cretaceous seawater and potential impacts on the cyst geochemistry is pending further inspection the ca isotope composition of the two dinoflagellate species shows identical trends of increasing 44 40ca between 73 and 67 ma the planktic foraminifer archaeoglobigerina australis and the benthic foraminifer nuttallides truempyi reveal the same increase of about 0 4 but are offset relative to the dinoflagellates by about 0 5 presumably due to species specific ca isotope fractionation bulk carbonate sediment shows significant scatter likely caused by changes in faunal composition and does not reproduce the trend revealed by the dinoflagellate and foraminifer records these observations demonstrate the importance of taxon specific records and careful determination of fractionation factors of selected archives and highlight complications arising from utilizing less suitable archives such as bulk sediments for 44 40caseawater reconstructions our records indicate strong changes in the marine ca cycle associated with the global temperature decrease towards the end of the cretaceous

isotope fractionation during ca exchange on clay minerals in a marine environment abstract in order to interpret marine porewater profiles it is mandatory to understand the behavior of calcium ca and its isotopes during cation exchange in marine sediments it has been proposed that the exchange of adsorbed ca 2 for ammonium which is a product of organic matter decomposition results in the releases of light ca from clay minerals into the porewater teichert et al 2009 in order to investigate the effect of ammonium on ca isotope fractionation experiments with clay mineral separates illites montmorillonite kaolinite and natural marine sediments from the north atlantic integrated ocean drilling project site u1306a in artificial seawater were carried out at different temperatures 4 14 21 c and ammonium concentrations 100 140 180 mm the results of the adsorption experiments carried out in artificial seawater show that during adsorption of ca 2 the light ca isotopes are favored over the heavier ca isotopes this effect is most prominent for the illite samples 1000ln 0 82 to 1 15 and kaolinite sample 1000ln 1 23 to 2 76 whereas montmorillonite and the natural marine sediments show smaller degrees of fractionation from the fluid in the range of 0 46 to 0 06 determination of the desorbed ca 2 is based on the adsorbed ca 2 left on the exchanger and reveals that the desorbed ca 2 has a significantly different isotopic signature from the surrounding fluid in general the degree of ca isotope fractionation is dependent on the ammonium concentration and does not show significant influence of temperature modeling the ca 2 desorption induced by ammonium adsorption demonstrates that according to the prevailing mineralogy and porewater sediment ratio desorbed ca 2 has the potential to shift the porewater isotopy by up to 2 5 and needs to be considered when interpreting ca isotope porewater profiles

smooth or oscillating late holocene sea level curve evidence from the palaeo zoology of fixed biological indicators in east australia and beyond abstract the nature of late holocene sea level change has important palaeo environmental implications for the understanding of past and present coastal oceanic and climatic systems this study develops a fixed biological indicator fbi method based on tubeworm barnacle assemblages in order to construct a late holocene sea level curve for south east australia it also compares changes within and between mid latitude regions of the southern hemisphere using the palaeo biology of inter tidal sub fossils that have provided time elevation data covering the past 5000 years five sites from around the mouth of the port hacking estuary 29 km south of sydney are described in detail the results suggest that rather than relative sea level describing a stable or smoothly falling pattern from a maximum of 1 0 m above present over the last 5000 years on the southeast australian coast there have been complex movements from a maximum of over 1 5 m with at least one marked fall between 3500 and 3400 yr bp and the possibility of a small positive oscillation around 1900 yr bp furthermore changes in the inter tidal species at our sites suggest that there was a period between 4300 and 2800 years where ocean temperatures were warmer than present our port hacking findings are compared with other studies from the east coast of australia as well as the pacific islands and brazil evidence from each location suggests a broad similarity in the timing of environmental events and marine fluctuations across an expanse of the southern hemisphere are such similarities coincidental or part of mechanisms common to mid latitude southern hemisphere regions

holocene reef development along the northeastern st croix shelf buck island u s virgin islands abstract eight cores were recovered from buck island underwater national monument u s virgin islands facies were defined based on recovered coral species fabrics observed in core slabs and thin sections and detailed notes on drilling character thirty six radiometric dates constrained the timing of reef accretion together these data provide a detailed history of reef development under varying regimes of sea level rise and physical oceanography holocene reefs around buck island initiated atop a broad antecedent bench at 13 16 meters below present sea level shelf flooding near buck island occurred as early as 9 500 years ago calbp but preserved reefs lagged by as much as 1 800 years earliest reef development was dominated by branching acropora palmata near the shelf edge and massive corals closer to buck island by 7 200 calbp a palmata apparently declined near the platform margin and was absent until ca 5 200 calbp throughout the study area over time the reefs closer to buck island built upward ca 16 m and seaward ca 50 m as the rate of sea level rise slowed and carbonate production increasingly exceeded the accommodation space that was being created reef topography and zonation became progressively more distinct with a palmata dominating the shallow reef crest branching coral apparently disappeared again between ca 3 030 and 2 005 calbp for reasons that are not clear this and the previous decline of a palmata mimic patterns seen around st croix and throughout the caribbean by 1 000 calbp the reefs close to buck island had largely assumed their present character and continued to track slowly rising sea level until the present around 1 200 calbp vertical accretion along buck island bar apparently ceased paradoxically the surface of this outer reef has historically been dominated by large stands of a palmata since the area was first described but rapid coral growth has not resulted in preservation of this species over the last millennium modern community structure mimics facies patterns seen in cores over the past 7 700 years the southern reef crest appears to have remained slightly shallower than its northern counterpart a condition that persists today observations after hurricane hugo in 1989 suggest that this difference in elevation is related to the piling up of debris on the broader southern reef crest by high waves from storms passing south of st croix also facies along the southern reef are more variable in species composition than their northern counterparts a condition that is exhibited by the modern reef community coral abundance and diversity in the cores total coral 20 30 dominated by a palmata are comparable to the community structure present in the late 1970s bythell et al 1993 hubbard et al 1993 in contrast fossil coral abundance and diversity are consistently higher than what was measured in the 1980s and early 1990s total coral 7 14 a palmata 2 after the onset of white band disease a putative pathogen which has recently decimated branching acroporids throughout the region the dominance of branching a palmata in the cores would seemingly reflect an absence of disease or other factors that would discourage its continued abundance in apparent contrast two lengthy gaps in the a palmata record reflect previous disappearances that roughly correspond to similar lapses elsewhere in the caribbean thus the spatial persistence of a species in the fossil record cannot necessarily be equated with its temporal continuity comparisons between changes in modern reefs on a time scale of decades and their fossil forebears must be made with great care understanding the role of short term changes and how they are reflected in the preserved record is thus critical to relating the late holocene a palmata gaps to the recent decline of the species this has important implications for our understanding of how preserved community structure relates to what actually existed in the past and could limit our ability to use the recent geologic record as a proxy to short term future changes in coral reefs

smooth or oscillating late holocene sea level curve evidence from cross regional statistical regressions of fixed biological indicators abstract what if any is the pattern of change of the late holocene sea level curve if a common pattern exists can it be better discerned in the non glaciated tectonically stable regions of the southern hemisphere and is sea level data more reliable from one type of marine sample than another to begin an investigation of these questions we present a review of regressing time elevation plots from the low to mid latitudes of the southern hemisphere based upon the differential between modern and past levels of various fixed biological indicators mainly calcareous tubeworms and corals stranded up to 2 m above present relative sea levels the sample sets come from our work in southeast australia and comparable work from north east australia the pacific islands and brazil we show that using evidence obtained from fixed intertidal tubeworm species there is no statistical exclusivity between the smooth and oscillating polynomials but corals are more problematic in situ tubeworm species with their reduced error bars in comparison to corals fulfil the condition of providing more robust results for statistical analysis regression curves based on these species point to cross regional similarities in the pattern of sea level movement of the last 6000 years across the lower latitudes of the southern hemisphere these statistical exercises while not able to yield definitive conclusions can highlight statistically equally likely alternative patterns of sea level movement which can then be tested by field evidence they can also give useful indications of the quality of sea level data obtained from different biological sources as in the difficulties in the use of corals compared to common intertidal tubeworm species

holocene sea levels in oceanic islands implications for the rheological structure of the earth s mantle abstract relative sea levels in oceanic islands that are situated sufficiently far from glaciated regions were studied in relation to the rheological structure of the earth s mantle the local hydro isostatic adjustment associated with the mantle flow from the oceanic side to an inland side depends on the size of the island the effective upper mantle viscosity and the elastic plate thickness the relative sea level has a significant dependence on the upper mantle rheology for islands with a radius larger than 10 km but it is almost independent of the upper mantle rheology for islands with a radius less than 10 km in other words the observed sea level changes in such small islands follow the global isostatic adjustment which depends strongly on the lower mantle viscosity in fact the relative sea levels in small oceanic islands impose important constraints on the lower mantle viscosity on the other hand the effective upper mantle viscosity and the elastic plate thickness are determined by analyzing the relative sea levels for islands greater than 10 km the observed sea level curves in japan and new zealand are consistent with the effective viscosity of the upper mantle equal to 2 to 6 10 21 poises the effective elastic plate thickness for japan and new zealand is estimated to be less than 50 km and greater than 100 km respectively the thickness of the lithosphere obtained by sea level curves in japan and new zealand is compatible with the results obtained by seismological studies

repeated occurrences of methanogenic zones diagenetic dolomite formation and linked silicate alteration in southern bering sea sediments bowers ridge iodp exp 323 site u1341 abstract diagenetic precipitates such as dolomite and the chemistry of residual deeply buried porewater often represent the only traces of past biogeochemical activity in marine sediments a 600 m thick sedimentary section recently drilled at integrated ocean drilling program iodp site u1341 on bowers ridge southern bering sea provides insight into such a 4 3 ma old paleo diagenetic archive hard lithified calcite dolomite layers and laminae of disseminated carbonate were recovered in diatom rich sediments over a depth range of 400 m carbon isotope values of the diagenetic carbonates between 16 6 and 14 4 vpdb and strontium isotope ratios of dolomites close to past seawater values suggest carbonate precipitation induced by the production of dissolved inorganic carbon dic during elevated rates of organic carbon mineralization primarily via sulfate reduction at shallow sediment depth below the paleo seafloor diagenetic carbonates at 280 440 m below seafloor were likely also produced by the intermittent onset of sulfate reduction coupled to the anaerobic oxidation of methane aom at sulfate methane transition zones smtz these microbially mediated processes do not occur in the sediment at this site at present but were likely connected to the presence of a methanogenic zone at 2 58 2 51 ma a minimum in sulfate concentrations in modern porewaters and low sedimentary ba al ratios resulting from former sulfate depletion are reminiscent of the presence of this large methanogenic zone the minimum in sulfate concentrations is reflected in a minimum in magnesium concentrations less radiogenic strontium and isotopically light calcium in the porewater it is proposed that magnesium was removed from the porewater during carbonate precipitation and volcanic ash alteration which occurred in the former methanogenic zone and also released strontium with a less radiogenic isotope ratio and isotopically light calcium into the porewater the isotopic composition of porewater calcium was also influenced by ammonium calcium exchange on clay minerals and carbonate recrystallization our study elucidates the response of porewater element concentrations and isotopic profiles interlinked with the formation of diagenetic carbonates to changes in the deposition of organic carbon in sediments of deeper water sites 2000 m water depth over prolonged timescales it shows that variations in biogeochemical processes in response to changes in oceanographic conditions and a dynamic subseafloor biogeochemical zonation have to also be taken into account at these deep water sites for a global assessment of organic carbon burial fluxes and remineralization

coral indicators of past sea level change a global repository of u series dated benchmarks fossil corals provide valuable data for reconstructing past sea levels as they are often well preserved in the fossil record and can be dated with u series methods here we present a global and internally consistent database of usingle bondth dated fossil coral sea level indicators including full consideration of all known associated uncertainties both vertical and chronological we include carefully determined taxon specific depth distributions rather than blanket depth uncertainty terms as used in most previous work this is based on a synthesis of extensive modern ecological information on depth ranges these ranges are found to be spatially variable between ocean basins between regions and on sub regional scales because depth itself is not limiting instead depth distributions arise from complex physical chemical and biological interactions with coral reef growth distribution and composition one of the main causes for recognition of the greater depth variability of coral taxa has been the routine inclusion of deep diving and rov surveys in coral ecological studies over the past few decades which has broken through the shallow water bias of early surveys by adding frequent observations on deeper occurrences although more are needed it is also clear from our assessment that coral habitat depth distributions must be determined on the species level to reduce uncertainties in reconstructions of past sea levels and that application to sea level studies then requires these studies also to identify fossil corals to the species level samples identified only to the genus level give rise to wide uncertainties in habitat depth and hence sea level our database contains extensive metadata to assist evaluations of dating quality as well as geomorphic and stratigraphic metadata we demonstrate with examples how such metadata can help to evaluate sea level reconstructions for example by identifying outlier points one example discusses the last interglacial lig where we use the available data with their uncertainties to assess probabilistically the time at which local sea levels exceed that of the present which yields a mean age of 124 6 ka with 95 probability bounds at 118 5 and 129 5 ka we conclude with identification of key outstanding issues relating to i current incomplete understanding of tectonic setting including the current lack of independent verification of uplift subsidence rates and reliance of somewhat unsatisfactory and circular use of the elevation of last interglacial deposits ii the depth distributions of coral taxa and iii the complete documentation of stratigraphic geomorphological and other contextual information with suggestions for strategies to address these issues

late pleistocene dune chronology near coastal new south wales and eastern australia abstract late pleistocene aeolian activity is manifested stratigraphically and geomorphically along the new south wales coastline in six different ways as barrier dunes cliff top and headland dunes sand sheets on slopes reworked barrier features onlapping coastal sand bodies and dustings the majority of activity took place over the last 40 ka bp paradoxically the present interglacial is characterised by extensive coastal dune fields while the last interglacial is not a fact that cannot be solely attributed to the destruction of older deposits through time the similarity in the degree of dune building between the holocene and the last glacial under very different climatic regimes may be indicative of the interaction of a multitude of climatic factors the effects of aboriginal occupation and burning also cannot be excluded australia wide aeolian activity has preferentially lingered over the northeastern and southern parts of the continent during the last glacial in the north this lingering reflects the progressive drying out of northern australia with the demise of trade wind cyclone and monsoon activities in the southeast it reflects the enhancement of stable extensive high pressure cells leading to the displacement of cold fronts and strong winds either southward towards tasmania or offshore into the tasman sea

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

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

silicate versus carbonate weathering in iceland new insights from ca isotopes to trace sources of ca in icelandic rivers we report elemental and ca isotope data for rivers high and low temperature groundwater basalt hydrothermal calcite including iceland spar and stilbite and heulandite which are two types of zeolites commonly formed during low grade metamorphism of basalt in agreement with previous research we find that rivers have higher 44 40ca values than basalt with a maximum difference of 0 40 this difference may reflect isotope fractionation in the weathering zone i e preferential uptake of 40ca during clay mineral formation adsorption and other geochemical processes that cycle ca however calcite 44 40ca values are also up to 0 40 higher than bedrock values and on a diagram of 44 40ca versus sr ca nearly all waters plot within a plausible mixing domain bounded by the measured compositions of basalt and calcite with glacial rivers plotting closer to calcite than non glacial rivers calcite and heulandite form during hydrothermal alteration of basalt in the deep lava pile and often occur together in metabasalts now exposed at the surface because heulandite 44 40ca values are 1 2 lower than basalt we suggest that 40ca uptake by heudlandite explains the relatively high 44 40ca values of calcite and that calcite weathering in turn elevates riverine 44 40ca values high mechanical erosion rates are known to facilitate the exposure and weathering of calcite which explains the isotopic contrast between glacial and non glacial watersheds using a mixing model we find that calcite weathering provides 0 65 of the ca in non glacial rivers and 25 90 of the ca in glacial rivers with silicate weathering providing the remainder icelandic hydrothermal calcite contains mantle carbon noting that zeolite facies metamorphism and hydrothermal fluid circulation are ubiquitous characteristics of basaltic eruptions and assuming that hydrothermal calcite in other basaltic settings also contains mantle carbon we suggest that the contribution of basalt weathering to long term co2 drawdown and climate regulation may be less significant than previously realized

magnesium in the marine sedimentary environment mgnh4 ion exchange abstract the release of exchangeable mg in marine sediments from displacement by ammonium ions was estimated by way of experimentally determining the parameters that govern this ion exchange equilibrium on solid geochemical phases smectite humic acid illite and opal we showed that a both the conditional selectivity constant as well as the solid concentration are important parameters in determining the relative contribution of ammonium exchangeable mg from smectite organic matter illite and opal and b that except in the cases where opal or organic matter concentrations are very high the clays are the dominant carrier phases for labile mg which is exchangeable by ammonium a model based on the sum of the contributions from the major geochemical phases present in the sediment reliably predicts the amount of mg released by exchange with ammonium in marine sediments

holocene key coral species in the northwest pacific indicators of reef formation and reef ecosystem responses to global climate change and anthropogenic stresses in the near future abstract the geological record of key coral species that contribute to reef formation and maintenance of reef ecosystems is important for understanding the ecosystem response to global scale climate change and anthropogenic stresses in the near future future responses can be predicted from accumulated data on holocene reef species identified in drillcore and from data on raised reef terraces the present study analyzes a dataset based on 27 drillcores raised reef terraces and 134 radiocarbon and u th ages from reefs of the northwest pacific with the aim of examining the role of key coral species in reef growth and maintenance for reef ecosystem during holocene sea level change the results indicate a latitudinal change in key coral species arborescent acropora acropora intermedia and acropora muricata was the dominant reef builder at reef crests in the tropics whereas porites porites australiensis porites lutea and porites lobata was the dominant contributor to reef growth in the subtropics between 10 000 and 7000 cal years bp when the rate of sea level rise was 10 m ka acropora digitifera acropora hyacinthus acropora robusta a abrotanoides isopora palifera favia stelligera and goniastrea retiformis from the corymbose and tabular acropora facies were the main key coral species at reef crests between 7000 and 5000 cal years bp when the rate of sea level rise was 5 m ka and during the following period of stable sea level massive porites p australiensis p lutea and p lobata contributed to reef growth in shallow lagoons during the period of stable sea level key coral species from the corymbose and tabular acropora facies have the potential to build reefs and maintain ecosystems in the near future under a global sea level rise of 2 6 m ka as do key coral species from the arborescent acropora facies and massive porites facies which show vigorous growth and are tolerant to relatively deep water low energy environments however these species are likely to experience severe mortality in upcoming decades due to natural and anthropogenic stresses consequently this damage will lead to a collapse in reef formation and the maintenance of reef ecosystems in the near future this study emphasizes the need for research into the conservation of key coral species

origin of rodingite forming fluids constrained by calcium and strontium isotope ratios in the leka ophiolite complex abstract alteration of oceanic lithosphere plays an important role in the global element cycling due to its dominant abundance on the earth s surface the formation of rodingites a ca rich lithology that occurs intimately associated with ca depleted serpentinite complexes is a widespread process during strong alteration of ocean floor lithologies and may represent a key process that influences the global ca cycle stable ca and radiogenic sr isotope compositions of rodingites and associated lithologies from the leka ophiolite complex norway preserve mantle signatures and thus provide evidence that the ca and sr sources for rodingitisation are dominantly mantle derived with no detectable seawater input the difference of 0 7 in 44 40ca of different phases found in the rocks is overall consistent with inter mineral fractionation at high temperatures related to the cao bonding environment but there are also indications for isotopic disequilibria between non cogenetic mineral phases while the water required for rodingite formation may originate from seawater the dissolved ca and sr involved in the mineral reactions during rodingitisation plg ca gros clz al can be balanced at a local scale being derived from the serpentinisation of mantle peridotites cpx1 h2o al srp chlorite ca cpx2 consequently rodingites do not act as a sink for oceanic ca instead they are a sink for ca released during serpentinisation of the oceanic lithospheric mantle

the ca isotopic composition of dust producing regions measurements of surface sediments in the black rock desert nevada dust is a relatively unconstrained flux in the geochemical cycle of ca the isotopic composition of dust derived ca has not been studied though it is an important part of any attempt at deciphering ca isotope based proxy records accordingly this study reports the elemental and calcium isotope geochemistry of 30 surface upper 0 5 cm sediments from an arid dust producer the black rock desert in northwestern nevada geochemical data for sequential water and 0 5 n hcl leaches meant to sample mobile ca and selected leached residues are presented along with x ray diffraction xrd determinations of major mineralogy bulk playa sediments have ca concentrations between 0 28 and 40 wt median 6 8 wt and calcite concentrations of 2 32 isotopically ca sampled by water leaches 60 of total ca though the degree of fractionation w a varies between 0 and 0 6 acid leaches which are the primary component of mobile ca in the sediments have 44casrm 915a values of 0 78 0 08 similar to the 44ca of modern nannofossil ooze and modern rivers this means that dust produced in closed continental basins likely has little isotopic leverage to change the ocean s isotopic composition and suggests that the ca isotopic composition of dust is tied to rivers weathering in addition while the ca concentration data in the water leach suggest that evaporative evolution controls the amount of ca in this reservoir the isotope data are inconsistent with this conclusion instead we hypothesize that adsorption of ca on clays controls the ca isotope systematics in the water leach this hypothesis requires that there is no significant isotopic fractionation during evaporite mineral precipitation and may suggest that sorption at rates appropriate for natural systems might fractionate differently than sorption at laboratory rates

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

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