holocene fringing reefs and sea level change in mangaia island southern cook islands abstract holocene relative sea levels in oceanic islands that are situated sufficiently far from glaciated regions provide basic information for the study of the melting histories of the continental ice sheets and of the rheological structure of the earth we have studied mangaia island south cooks as one such oceanic island located in the middle pacific ocean in addition to the usual geological and geomorphological observations of geomorphic features associated with former shorelines we have used a portable drilling sampler for shallow borings of coral reefs geological and geomorphological studies of the coast of mangaia island have revealed that there was a higher sea level than the present in the mid holocene the heights and ages of emerged microatolls on the emerged bench indicate that the sea reached a maximum level of 1 7 m around 4000 3400 yr b p and then emergence is considered to have occurred between 3400 and 2900 yr b p at the same time the reef crest formed in the period from 5000 to 3400 yr b p emerged above the sea and suffered erosion as a result of this change in sea level upward reef growth from the fore reef slope began to form a new reef crest by 2000 yr b p to seaward of the old reef crest the reef margin of mangaia grew outward intermittently with seaward jump of the reef front in accordance with a fall of sea level in the late holocene the presence of fossil reef crests or eroded algal ridges on modern reef flats is a rather common feature in the south pacific the geomorphic development of such features on reef flats can be explained by the effect of the late holocene fall in sea level

post glacial sea level rise from a coral record at huon peninsula papua new guinea dating of coral reef terraces can provide a record of changes in sea level which should be pronounced during the transition between glacial and interglacial periods cores drilled from coral reefs at barbados in the equatorial west atlantic1have revealed the sea level changes that occurred during the younger dry as event at the end of the last glacial maximum 11 000 yr bp it has not been known however whether pacific coral reefs can grow at a rate sufficient to keep up with the rise in sea level during such a transition here we report results obtained from a 52 m drill core from the post glacial reef at huon peninsula papua new guinea spanning the interval from 7 000 to 11 000 14c yr bp which show that coral growth kept pace while the relative sea level rose by 50m although the tectonic environment is very different from that at barbados the two records compare well when corrections are made for local tectonic uplift showing that sea level rise was similar at both locations the rate of rise was greatest between 9 000 and 10 00014c yr bp corresponding to the time of the younger dryas

late quaternary reef growth and sea level in the maldives indian ocean abstract based on rotary drilling and radiometric and u series dating we present the first comprehensive data on holocene reef anatomy and sea level rise as well as nature and age of underlying pleistocene limestone in the maldives holocene reefs in rasdhoo atoll central maldives are composed of four facies including 1 robust branching coral facies 2 coralline algal facies 3 domal coral facies and 4 detrital sand and rubble facies branching coral and coralline algal facies predominate the marginal reefs and domal corals and detrital facies preferentially occur in a lagoon reef in addition microbialite crusts are found in lower core sections of marginal reefs microbialites formed during the early holocene in reef cavities holocene reef thickness ranges from 14 5 m to 22 m reef growth started as early as 8 5 kyr bp marginal reefs accreted in the keep up mode with rates of 15 m kyr rate of sea level rise significantly slowed down from 7 6 kyr bp and subsequently gradually rose with rates

holocene reef sequences and geochemistry britomart reef central great barrier reef australia holocene reef development was investigated by coring on britomart reef a mid shelf reef 23 km long and 8 km wide situated 120 km north of townsville in the central great barrier reef gbr two holes were drilled britomart 1 on a lagoon patch reef and britomart 2 on the windward reef crest the holocene reef 25 5 m is the thickest yet recorded in the gbr and overlies an uneven substrate of weathered pleistocene limestone mineralogical and geochemical analyses show that magnesian calcite and aragonite were converted to low mg calcite below the holocene pleistocene disconformity corals above the interface have 7500 8500 ppm sr but 1650 1500 ppm just below it decreasing to 400 800 ppm downwards the intermediate sr values could be due to partial replacement of aragonite by calcite or higher original sr content in the corals three units are recognized in the holocene 1 coral boundstone unit 2 coral framestone unit and 3 coral rudstone unit the coral boundstone unit forms the top 5 m of both cores and is algal bound coral rubble similar to the present reef top the coral framestone unit is composed of massive head corals diploastrea heliopora and porites sp and is currently forming in patch reefs situated in the lagoon and along the reef front the coral rudstone unit comprises coral rudstone and floatstone with unabraded and unbound coral clasts in muddy matrix this matrix may be up to 30 sponge chips radiocarbon dating indicates the reef grew more rapidly under the lagoon than under the reef front from 7000 to 5000 yr bp the rate of reef growth matched existing estimates of sea level rise but lagged approximately 1000 years 5 10 m behind it most of the reef mass accumulated between 8500 and 5000 yr bp as a mound of debris perhaps stabilized by seagrasses or algae accretion of the reef top in a windward direction between 5000 and 3000 yr bp created the present steep reef front profile

rhodolith assemblages from the lower tortonian carbonate ramp of menorca spain environmental and paleoclimatic implications abstract lower tortonian distally steepened carbonate ramp of menorca mostly consists of foramol and rhodalgal facies deposited in inner middle ramp ramp slope and outer ramp settings red algae are abundant from the middle ramp to the lower part of the slope and their taxonomic assemblages are clearly related to the bathymetric position melobesioids percentage increases basinward passing from 55 8 in the middle ramp to 97 in the toe of slope mastophoroids are more abundant in the middle ramp 43 1 and decrease toward deeper paleoenvironments 1 2 lithophylloids and sporolithaceans appear as accessory components from the middle ramp to slope settings the percentage of melobesioids and mastophoroids observed in the middle ramp suggest that growth of the rhodoliths started in a water depth below 10 20 m the deepest occurrence of the rhodoliths is in the ramp slope environment where the dominance of melobesioids and the low percentage of shallower water subfamily suggests a water depth range of 70 to 100 m shape and structure of rhodoliths are indicative of high energy conditions in all ramp settings and they do not reflect a decrease in hydrodynamic energy related to water depth increase these conditions are related to the presence of unidirectional currents that produced cross bedded grainstones existing in the middle ramp ramp slope and at the toe of the ramp slope settings the high percentage of mastophoroids in the shallowest environments and the presence of lithoporella and sporolithon in the coralline assemblages suggests that carbonate production took place in tropical waters

morphology of fore reef slopes and terraces takapoto atoll tuamotu archipelago french polynesia central pacific the tectonic sea level and coral growth control abstract a dataset of 41 bathymetric profiles detected by satelline imagery and echo sounding to a maximum depth of 38 m along the fore reef slopes of takapoto atoll tuamotu plateau french polynesia central pacific were qualitatively and quantitatively analyzed in order to identify the main geomorphological features in addition scuba diving investigations from a selected site resulted in defining coral composition and cover rate six distinct fore reef sectors were morphologically differentiated on the basis of seaward extension and slope gradient only the north end and a restricted area of the mid south east side extend seawards over an average distance of 150 m with a relatively low gradient 23 38 most of the outer slope areas are narrow 10 m high outer reef crest like reliefs 0 5 m 1 5 m high pinnacles 2 m 17 m high coral heads

syn depositional alteration of coral reef framework through bioerosion encrustation and cementation taphonomic signatures of reef accretion and reef depositional events the development of coral reef framework and the preservational character of both in situ and rubble coral is strongly influenced by a range of physical chemical and biologically mediated taphonomic processes these operate at or just below the reef framework water interface and can be defined as having either a constructive or destructive effect upon primary reef framework i e coral constituents constructional activities add additional calcium carbonate to the primary framework structure via secondary framework growth and early cementation destructive processes which remove or degrade primary and secondary framework carbonate are associated with the effects of either physical mainly storm disturbance or biological erosion termed bioerosion key bioeroding groups include the grazing fish and echinoid groups as well as the activities of an array of infaunal borers these include specific groups of sponges bivalves and worms termed macroborers as well as cyanobacteria chlorophytes rhodophytes and fungi termed microborers the relative importance of each process and the rates at which they operate vary spatially across individual reef systems in addition many of these processes leave distinctive signatures on or in the coral framework in some cases e g calcareous encrusters these are the skeletons of the organisms themselves whilst in other cases the organism may leave behind a trace of their activity e g macro and microborers these represent useful palaeoenvironmental tools firstly because they often have good preservation potential and secondly because the range and extent of many of the individual species groups and processes involved exhibit reasonably well constrained environment and or depth related distributions as a result these taphonomically important organisms or processes can be used to delineate between reef environments in core or outcrop and to aid the interpretation of reef depositional processes and events this review summarises current understanding regarding the distribution of these species processes within contemporary reef settings and considers the suites of taphonomic signatures that may aid in the recognition and interpretation of depositional environments and events

sea level rise and coral reef development of northwestern luzon since 9 9ka abstract coral reef growth and relative sea level record for the early mid holocene are established from three boreholes drilled on a raised holocene reef at currimao northwestern luzon philippines age control is provided by 230th dates of 13 corals mostly in living position the cores cover a depth interval from 3 8 m above to 26 7 m below present mean sea level msl and consist of four lithofacies including 1 reef facies 2 bioclastic facies 3 clayey facies and 4 tuffaceous facies the ages of dated corals vary from 6588 27 ya at 1 4 m below msl to 9855 42 ya at 22 m below msl results of this study indicate that the reef started growing about 9 9 ka when the minimum sea level relative to the western luzon coast was about 27 m below msl after tectonic correction during 9 2 8 2 ka reef accretion rate was as high as 10 13 m ky coral reef developed to near paleo sea level at about 6862 28 ya and emerged due to tectonic uplift the sea level curve of currimao is generally similar to that of the western australia coast but at least 8 11 m higher than that of tahiti from 10 to 8 5 ka

deglacial sea level record from tahiti corals and the timing of global meltwater discharge the timing of the last deglaciation is important to our understanding of the dynamics of large ice sheets1 and their effects on the earth s surface2 3 moreover the disappearance of the glacial ice sheets was responsible for dramatic increases in freshwater fluxes to the oceans which probably disturbed the ocean s thermohaline circulation and hence global climate4 7 sea level increases bear witness to the melting of continental ice sheets but only two such records from barbados8 9 and new guinea10 11 corals have been accurately dated but these corals overlie active subduction zones where tectonic movements are large and often discontinuous especially in new guinea so the apparent sea level records may be contaminated by a complex tectonic component here we date fossil corals from tahiti which is far from plate boundaries and thus is likely to be tectonically relatively stable and remote from the locations of large former ice sheets the resulting record indicates a large sea level jump shortly before 13 800 calendar years bp which corresponds to meltwater pulse 1a in the barbados coral records8 9 the timing of this event is more accurately constrained in the tahiti record revealing that the meltwater pulse coincides with a short and intense climate cooling event12 15 that followed the initiation of the bolling allerod warm period12 16 but preceded the younger dryas cold event by about 1 000 years

late quaternary paleolandslides on the coral terraces of huon peninsula papua new guinea abstract many landslides disrupt the coral terraces at northeast huon peninsula papua new guinea each landslide is younger than the youngest terrace which it intersects and is older than the oldest coral reef or shoreline that overlies it the ages of the raised coral reefs and terraces were established by previous studies using radiocarbon and uranium series dating the times of occurrence of 26 late quaternary landslides are reported here 7 are based on new radiocarbon dates from in situ corals or molluscs associated with landslide deposits and the remainder are based on terrace ages that were established previously the landslides include slumps block slides and block flows which mostly involve failure of coral limestones of the terraces and debris flows which originate from large landslides that cut through the coral limestones into underlying fan delta and tuffaceous sedimentary rocks the proportion of terrace area affected by late quaternary landslides ranges from 50 per km2 and depends on average gradient of the landsurface tectonic uplift rate and the thickness and geometry of the raised reefs and terraces clusters of landslides which occurred at about 800 1250 and 6300 7800 yr bp may have been triggered by large earthquakes which also caused metre scale coseismic uplift however we did not identify landslides that could have been associated with every large coseimic uplift that has been documented in this region

holocene sea level changes in french polynesia abstract new data on holocene sea levels have been obtained in 28 atolls and 10 high islands in the society tuamotu gambier and austral islands in an area of the south pacific as wide as western europe sea level indicators are often very accurate 0 1 m and include exposed corals abandoned algal ridges and reef frameworks in growth position emerged tidal notches and skeletal reef conglomerates in which the position of the former low water level at the time of cementation has been determined by petrological analysis over 110 new samples have been dated by radiocarbon the overall pattern is that of a msl standstill at 0 8 1 0 m between 5000 and 1250 yr b p a set of radiocarbon dated samples covering the period 4500 1250 yr b p almost continuously is evidence that lasting msl drops could not ever have occurred below 0 7 m throughout this time the highest sea level peak about 1 0 m seems to have been reached between 2000 and 1500 yr b p since 1500 yr b p msl has been dropping gradually from about 1 0 m to the present position which has been reached only recently some islands show however a slightly different pattern the holocene emergence is smaller than average in moorea and tahiti and larger in rurutu makatea anaa and possibly hereheretue some data suggest also the possibility of a slight increase in the holocene emergence towards the south possible geodynamic isostatic oceanic and climatic causes of the sea level variations observed are discussed

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

characterization of various stages of calcitization in porites sp corals from uplifted reefs case studies from new caledonia vanuatu and futuna south west pacific abstract this study focuses on the processes of calcitization under meteoric conditions based on observations and analyses of a series of subaerial fossil corals of the genus porites collected from emerged holocene and pleistocene reefs in the pacific ocean we can establish two types of low magnesian calcite lmc precipitates according to their textural characteristics after their transformation from the initial aragonitic skeleton to the calcitized corals in the first variety lmc1 the calcite contains remnants of the original exoskeleton structure in situ insoluble organic tissues pieces of aragonite needles while in the second variety lmc2 filling the primary inter skeletal macro pores such relicts are not present such textural segregation is faithfully reflected in the elemental data on some parts of calcitized corals lmc1 is characterized by mg2 sr2 and mn2 compositions inherited from the aragonite precursor indicating a formation in a semi closed intra skeleton diagenetic environment in disequilibrium with the meteoric bulk aquifer water lmc2 has a chemistry indicative of equilibrium with ambient bulk meteoric water these chemical characteristics can be likened to a two fold mechanism a fine scale process neomorphism typified by the concomitant dissolution of intra fabric aragonite and re precipitation of the lmc1 resulting from the biogenic skeleton and marine waters followed by the cementation of the inter fabric macro voids by an allochthonous subaerial and meteoric lmc2 in the other parts of calcitized corals lmc1 and lmc2 have similar trace element contents in mg2 and sr2 the chemical data are consistent with formation by partial skeletal dissolution followed eventually by cementation of primary voids lmc2 and secondary voids lmc1 by calcite in equilibrium with meteoric bulk aquifer water these two mechanisms of the calcitization of skeletal aragonite mainly differ in the space and time length scales of the intervening transport step and are commonly found juxtaposed in the same thin section taking into account such a heterogeneity is a real challenge for the development of predictive models assessing the effects of diagenetic products on paleoclimatic reconstructions

microbialite development patterns in the last deglacial reefs from tahiti french polynesia iodp expedition 310 implications on reef framework architecture abstract the widespread occurrence of microbialites in the last deglacial reef frameworks 16 6 ka bp implies that the accurate study of their development patterns is of prime importance to unravel the evolution of reef architecture through time and to reconstruct the reef response to sea level variations and environmental changes the present study is based on the sedimentological and chronological analysis 14c ams dating of drill cores obtained during the iodp expedition 310 tahiti sea level on the successive terraces which typify the modern reef slopes from tahiti it provides a comprehensive data base to investigate the microbialite growth patterns i e growth rates and habitats to analyze their roles in reef frameworks and to reconstruct the evolution of the reef framework architecture during sea level rise the last deglacial reefs from tahiti are composed of two distinctive biological communities 1 the coralgal communities including seven assemblages characterized by various growth forms branching robust branching massive tabular and encrusting that form the initial frameworks and 2 the microbial communities developed in the primary cavities of those frameworks a few meters 1 5 to 6 m below the living coral reef surface where they heavily encrusted the coralgal assemblages to form microbialite crusts the dating results demonstrate the occurrence of two distinctive generations of microbialites the reefal microbialites which developed a few hundred years after coralgal communities in shallow water environments whereas the slope microbialites grew a few thousands of years later in significantly deeper water conditions after the demise of coralgal communities the development of microbialites was controlled by the volume and the shape of the primary cavities of the initial reef frameworks determined by the morphology and the packing of coral colonies the most widespread microbialite development occurred in frameworks dominated by branching thin encrusting tabular and robust branching coral colonies which built loose and open frameworks typified by a high porosity 50 in contrast their growth was minimal in compact coral frameworks formed by massive and thick encrusting corals where primary cavities yielded a low porosity 30 and could not host a significant microbialite expansion

bathymetric zonation of modern microborers in dead coral substrates from new caledonia implications for paleodepth reconstructions in holocene corals abstract microboring endoliths were studied in dead modern corals collected at various depths and in growth position on la surprise atoll in new caledonia eight taxa of microborers were regularly observed three cyanobacteria hyella caespitosa mastigocoleus testarum and plectonema terebrans two chlorophytes ostreobium quekettii and phaeophila dendroides and three fungal forms dodgella priscus and two unidentified fungi the relative abundance of each taxon was determined in the modern corals throughout the studied sampling interval from 0 down to 40 m water depth this allowed us to propose for the first time a bathymetric model based on microendolith assemblages colonizing in situ hard substrates of corals in this model the occurrence of the cyanobacteria hyella and mastigocoleus indicates a bathymetric range from 0 down to a water depth of 3 and 6 m respectively the chlorophyta o quekettii associated with the cyanobacterium p terebrans and fungi is dominant from 10 to 40 m depth which is the lower limit of our sampling the distribution ranges of individual taxa observed in the dead coral substrates from new caledonia are much narrower than those reported in the literature for other substrates the bathymetric model based on distribution of microborers in modern corals was then applied to interpret the trace assemblages of microborers observed in holocene corals collected by drilling on two reef sites of new caledonia la surprise islet in the vicinity of the sampling sites of the modern corals and the barrier reef of bayes on the ne coast of grande terre the paleodepth interpretations performed at various levels along the cores allow identification of several shallowing upward sequences during the last 7000 years of reef growth in new caledonia differences in the thickness of these sequences between la surprise and bayes sites were interpreted as differences in the space available for accommodation between the two sites in turn related to the differential subsidence that affected new caledonia during holocene times the use of the microendolith trace assemblages in paleodepth reconstructions of holocene reefs from new caledonia allowed detection of relative sea level variations finer than those deduced from changes in coralgal assemblages

successive reef depositional events along the marquesas foreslopes french polynesia since 26 ka abstract bathymetric surveys of submarine platforms and terraces of the tropical marquesas archipelago french polynesia coupled with sedimentological and paleoecological analyses and radiometric dating of dredged rocks reveal the occurrence of several distinct intervals of reef deposition during the last deglacial sea level rise i e the last 26 000 yr or 26 ky five facies related to reef shallow water and deeper depositional zones have been identified on the basis of their respective biological assemblages facies 1 2 and 3 consist of in situ scleractinian corals mainly porites associated with thick crusts of coralline algae species hydrolithon onkodes h reinboldii lithophyllum pustulatum group and widespread vermetids and victoriellinid foraminifers these assemblages are typical of high energy shallow water reef settings i e upper forereef reef crest and outer reef flat and inner reef flat respectively facies 4 is characterized by the prevalence of halimeda plates mixed with debris of amphiroa and amphistegina spp these algae generally inhabit the inner parts of the reef flat and backreef zones but also the relatively protected deeper parts of outer reef slopes facies 5 is composed of large broken mollusc shells oysters embedded in fine grained sediments with significant numbers of deep living coralline algae mesophyllum sp and planktonic foraminifers locally mollusc shells are covered with microbialite crusts the replacement of shallower assemblages by deeper ones is interpreted as an upward deepening sequence identification of morphological and biological features combined with coral dating provide evidence of 4 reef generations rg between 26 and 9 ka now ranging from 138 to 58 m in depth 1 rg 0 from 26 to 19 ka in the 125 115 m depth interval 2 rg 1 from 18 to 15 ka between 110 and 95 m 3 rg 2 from 14 to 11 5 ka between 80 and 68 m and 4 rg 3 younger than 11 5 ka at around 55 to 60 m the first three units exhibit clear zonation from upper reef slope to reef flat their development was probably interrupted by abrupt rises in sea level and or drastic climate changes such a scenario is similar to observations reported in barbados and hawai i where rapid rises in sea level interpreted as reflecting major melting events of continental ice caused the drowning of reefs the younger unit refers to coral banks similar to those in modern marquesas environments the replacement of typical coral reefs by coral banks may reflect an increase el nino southern oscillation enso frequency and intensity inimical to reef development in the last 12 ka

coral reef records of quaternary changes in climate and sea level abstract although coral reefs have long been regarded as documenting climate change largely through its effects on sea level the temporal continuity and sensitivity to disturbance of their records appears to fall short of those provided by ice cores deep sea sediments and similar proxies the reasons for this anomaly relate principally to shifts in the loci of deposition the temporal windows in which accretion has been able to occur in a given place reflecting sea level at a particular height relative to the present datum are severely constrained where it has been possible coral growth and reef accretion have been and are sensitive to the signals provided by the environment in the form of changes in water depth temperature salinity nutrient supply turbidity and ph acidity concomitant with changes in sea level itself changes in these environmental parameters are directly or indirectly controlled by climate however because the responses of corals to stimuli are commonly site specific and the nature of the changes evoked so disparate it is likely that only major sea level cycles will provide evidence of a consistent global response in what has been a segmented record

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

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

210po 210pb dating of recent volcanic eruptions on the sea floor the globe encircling mid ocean ridge system accounts for most of the earth s volcanism and influences its heat budget morphology and the composition of the oceans it is therefore important to constrain the size frequency and compositional variability of ridge eruptions but this is made difficult by the remoteness of much of the sea floor and the paucity of applicable radioactive chronometers remote monitoring has provided indirect evidence for active ridge volcanism1 3 which in some cases has been strengthened by submersible observations4 5 but it has not been possible to date these eruptions directly here we present a new chronometer based on 210po 210pb radioactive disequilibrium which allows us to date glassy eruption products within a few years of their eruption our first results on lavas from 9 50 n on the east pacific rise confirm that the ridge erupted only months before sample collection and indicate that the eruptions extended over at least one year the chronometer begins with po volatilization during eruption all glasses analysed were 75 100 degassed a crystalline pillow interior was 20 degassed however implying that the flow surface may control po degassing during deep submarine eruptions although the 210po 210pb chronometer is useful for only a short time frame it should prove valuable for dating recent but unobserved submarine eruptions and determining details of eruptive sequences

crustose algal frameworks from the eocene alpine foreland abstract upper eocene algal limestones of the eastern alpine foreland in austria contain three different types of crustose algal frameworks these reveal several similarities with the present day coralligene de plateau of the mediterranean sea but the framework types differ in the crust forming algal taxa the sedimentary regime and the environmental setting 1 the coralline coral frameworks develop from siliciclastic sediments and show a succession from coverstones to bindstone to cruststone initiation of this framework in a siliciclastic regime is only possible because of the occurrence of neogoniolithon sp a species that is able to grow on fine grained soft substrate the onset of a dense crustose framework was related to the reduced sediment input and the occurrence of lithothamnion sp which is able to form cruststones 2 pure coralline algal frameworks are restricted to cruststones dominated by both lithothamnion sp and neogoniolithon sp they formed on top of maerl megaripples during calm periods and shed crustose fragments towards depressions which allowed framework progradation 3 peyssonneliacean dominated frameworks occur with intercalations of coralline algal crusts they formed in muddy environments interpreted as protected depressions between maerl dunes we found that crustose frameworks are controlled by three factors 1 sediment input low input favors the growth of frameworks while coarser grained siliciclastics cause burial of initial algal crusts terrigenous mud influences water turbidity and thus favors the occurrence of peyssonneliacean algae 2 taxonomic composition framework formation requires the existence of crustose algal taxa which are able to grow directly on fine grained soft substrate neogoniolithon sp polystrata alba or to encrust and stabilize coarse grained particles lithothamnion sp and or to form multiple successions of dense crusts lithothamnion sp p alba phymatolithon sp characteristically encrusts corals but it does not contribute to the frameworks surprisingly algae do never form protuberances within the frameworks even if they show protuberant growth forms in maerl sediment 3 substrate stability as a function of substrate composition and hydrodynamic energy due to their occurrence on maerl bottoms and the lack of evidence for submarine hardgrounds the settlement of crustose buildups requires low tidal current activity and or wave agitation

quaternary development history of coral reefs from west indian islands a review the western indian ocean results from a complex geological history implying both plate motion since about 180 million years and volcanic hot spot activity since about 68 million years this region exhibits a myriad of islands different in nature and origin including continental remnants madagascar the granitic seychelles high volcanic islands reunion mauritius rodrigues the comoros high and low lying carbonate reef platforms the carbonate seychelles the french scattered island group agalega islands and a few submerged reef banks geyser nazareth saya de malha this region contains all known types of reefs fringing barrier atoll platform and bank the data about reef development history over the quaternary were gained mainly from two distinct sources boreholes and emerged outcrops reef drilling indicates that modern reefs started regionally to grow from about 10 000 9600 years bp rates of vertical reef accretion ranges from 0 2 to about 10 mm year according to exposure and shape of coral builders the sea level curves reconstructed from vertical reef accretion and lagoon deposition curves express a rapid rise in sea level at rates averaging 6 mm year between 10 000 and 7500 7000 years bp with a stabilization at the present position around 2500 3000 years bp there are significant variations in the composition and distribution of dominant reef building coral assemblages and facies framework versus detritus according to exposure to wave energy frameworks composed of robust coral branching assemblages mainly acropora robusta a humilis groups isopora palifera dominate in higher energy settings while those with domal and tabular branching forms mainly porites various faviids acropora hyacinthus group are best represented in lower energy to protected environments detritus reefs are best developed in sheltered sites the recent contribution of some dominant coral species in modern wio reefs seem to have resulted from their delayed arrival in the region as controlled by the regional prevailing surface circulation south equatorial current and agulhas current and or by the competency period of their larvae coral based geochemical records suggest that during the mid holocene the seasonal variability of sea surface temperatures was lower than today the reconstruction of the wio pleistocene reef history is chiefly based on a limited number of exposed reef remains deposited during the last interglacial mis 5 5 stage 129 000 125 000 years bp at present culminating at elevations ranging from 20 to 9 m with respect to present mean sea level such differences in elevation can be explained by a differential tectonic behaviour of reef bearing substrates from stable continental areas to subsiding volcanic islands the existence of older reef generations plio pleistocene was identified from coral rich inclusions trapped into pyroclastites of comoro volcanoes

variations in pleistocene coral assemblages in space and time in southern and northern central ryukyu islands japan we studied the taxonomic and morphological compositions of pleistocene coral assemblages in 24 quadrats in okinawa jima southern central ryukyus and in 14 quadrats in kikai jima northern central ryukyus a total of 72 species belonging to 35 genera were identified in okinawa jima whereas 65 species coming under 33 genera were recorded in kikai jima cluster analysis of the bray curtis bc similarity coefficient produced 8 coral associations and 3 ungrouped taxa they correspond to a wide range of reef environments from shallow lagoon to lower reef slope settings the analysis of taxonomic similarities among quadrats leads to the identification of 7 clusters and 5 isolated quadrats the segregation of quadrats indicating a same reef zone into distinctive groups or single branches in the cluster diagram reflects the within reef slope variability in community structure specifically encrusting acropora palifera indicative of the upper reef slope zone shows a great variability of associated coral species and morphologies we also report differences in the geographic distribution of acropora palifera and platygyra contorta between present day and pleistocene reefs which may be linked to changes in sea surface temperature the decrease in the total species and generic richness recorded in modern reefs is not clearly detected in the fossil record in addition mds ordination of the bc similarities highlights patterns of reef zonation and geographic differences in taxonomic composition one way tests of similarity anosim show that differences in the composition of upper reef slope coral assemblages between okinawa jima and kikai jima are not larger than those observed between southern and central okinawa jima finally we report various types of coral successions sea level changes resulted in transitions from one reef zone to another whereas local disturbances are likely to have been responsible for the successions of distinctive coral assemblages with overlapping depth ranges which reflect the within reef zone variability

time lapse side scan sonar imaging of bleached coral reefs a case study from the seychelles abstract high resolution 675 khz side scan sonar surveys were collected six and thirty months after a major coral bleaching event in the seychelles the surveyed areas contain four different reef morphologies the distribution of which depends on water depth and distance from the shoreline these four reef types also have different coral densities and colony morphologies branching or mixed massive branching textural analysis based on first order statistics unsupervised cluster analysis and mann whitney u tests showed a correlation between recorded backscatter response and reef type that is attributed to the link between community composition and rugosity on a millimetre to tens of metre scale branching coral colonies are found to be relatively good scatterers of acoustic energy and result in a broad intermediate to high intensity response massive coral colonies and reefs with a hard carbonate pavement are found to be principally reflectors of the acoustic energy resulting in a narrow low intensity response comparison of the two surveys separated in time by two years showed seabed texture to change most significantly over the reef areas that contained the highest coral abundances and mortality rates in particular the disintegration of dense branching colonies that suffered almost 100 mortality during the bleaching event resulted in a characteristic loss of intermediate to high backscatter intensity the work demonstrates the contribution that side scan sonar could make in the assessment of loss of rugosity following a bleaching episode which has important implications to both the recovery of the reef itself and the abundance and distribution of associated reef organisms

assessing subsidence rates and paleo water depths for tahiti reefs using u th chronology of altered corals we present uranium thorium chronology fora 102 m core through a pleistocene reef at tahiti french polynesia sampled during iodp expedition 310 tahiti sea level we employ total and partial dissolution procedures on the older coral samples to investigate the diagenetic overprint of the uranium thorium system although alteration of the u th system cannot be robustly corrected diagenetic trends in the u th data combined with sea level and subsidence constraints for the growth of the corals enables the age of critical samples to be constrained to marine isotope stage 9 we use the ages of the corals together with o based sea level histories to provide maximum constraints on possible paleo water depths these depth constraints are then compared to independent depth estimates based on algal and foraminiferal assemblages microbioerosion patterns and sedimentary facies confirming the accuracy of these paleo water depth estimates we also use the fact that corals could not have grown above sea level to place a maximum constraint on the subsidence rate of tahiti to be 0 39 m ka with the most likely rate being close to the existing minimum estimate of 0 25 m ka

last interglacial reef facies and late quaternary subsidence in the maldives indian ocean abstract to date there is hardly any knowledge of facies and age of pleistocene reef limestone in the maldives likewise there are no robust estimates of quaternary subsidence in this major shallow water carbonate platform and reef area in a core recovered on the windward margin of rasdhoo atoll in the central part of the archipelago pleistocene coralgal grainstone facies belonging to marine isotope stage mis 5e were recovered underlying a holocene reef succession 14 5 m below modern sea level based on the occurrence of shallow water stony corals such as isopora palifera and possibly acropora gr robusta high energy coralline algae including porolithon onkodes in part associated with vermetids and grain supported limestone texture the paleoenvironment is interpreted as a shallow back reef area with a paleo waterdepth of

coralline algae corallinales rhodophyta in western and central mediterranean messinian reefs abstract coralline algae are common components in messinian reefs in the sorbas basin in se spain and in the salento peninsula southern italy they occur encrusting coral skeletons and other bioclasts forming rhodoliths and as fragments in back reef reef framework and proximal to middle slope facies corallines also occur in halimeda boundstones associated to coral reefs in contrast no coralline algae have been recorded in the fine grained distal slope deposits in both areas and in lagoonal marly limestones in salento the relative abundance of corallines in reefs and their species richness is significantly higher in the salento platform than in the intermontane sorbas basin which was affected by terrigenous influx neogoniolithon brassica florida and spongites fruticulosus dominate the shallow water assemblages lithophyllum records peak at the base of reef core and upper slope deposits around 20 m palaeodepth and phymatolithon calcareum and species of lithothamnion are most abundant in deeper slope facies the main components of the messinian mediterranean reef coralline assemblages are extant species common in the mediterranean and along the north atlantic coast from morocco and the canary islands to the british islands a few such as spongites fruticulosus and phymatolithon calcareum have been living in the mediterranean region for more than 25 ma four species still live in the indo pacific but disappeared from the mediterranean during the messinian salinity crisis the typical components of present day indo pacific coral reefs do not occur in the mediterranean messinian reefs the mediterranean atlantic character of the messinian reef corallines reflects the decrease in tropical biotas in the mediterranean throughout the miocene probably related to global cooling and isolation of the mediterranean from the indian ocean since the middle miocene

fringing reef growth and morphology a review abstract fringing reefs are generally not simple veneers of coral growth along tropical shorelines extensive research over the past few decades based on radiocarbon dating of holocene reef deposits has indicated that they can develop in a complex variety of ways even though the surface morphology may appear relatively simple the principal factor that appears to determine the growth and morphology of fringing reefs is the available accommodation space sea level fluctuations are important primarily because the sea surface determines the absolute accommodation space for a given reef this means that a reef established during a period of sea level rise will be able to accrete vertically as space is created above it if however the reef establishes at or grows to the sea surface thereby occupying all the available accommodation space it can no longer accrete vertically and begins to build laterally the morphology and chronostratigraphy of a range of holocene fringing reefs are described on the basis of which six fringing reef growth models are identified in model a the fringing reef is established at depth and primarily accretes vertically towards the sea surface reef growth in model b initiates at sea level and due to the lack of vertical accommodation space grows laterally model c has a similar morphology to model b however the reef progrades over a non reefal sediment wedge episodic lateral and vertical growth occurs in model d with a stepwise progradation of the reef front the remaining models are characterised by seaward reef framework behind which unconsolidated sediments accumulate in model e reef crest growth forms a barrier leading to the development of a backreef lagoon model f has a similar morphology to model e except that the reef crest is formed by hurricane rubble accumulation rather than framework accretion and is periodically reworked

environmental significance of microbialites in reef environments during the last deglaciation in situ microbialites occurring in reef rocks dredged between 80 and 130 m water depth on the modern fore reef slopes of tahiti and the marquesas islands yield ages ranging from 17 100 2900 to 4410 2250 years bp suggesting that they played a prominent role during the last deglacial sea level rise microbialites developed in both shallow and deep water depositional environments where they characterize various zones of the reef tracts reef crests upper reef slopes deep fore reef slopes reflecting contrasting scenarios of microbialite development involving reefal microbialites in shallow water settings and slope microbialites that formed in environments deeper than 10 20 m and extending down to more than 100 m reefal microbialites correspond to a late stage of encrustation of the dead parts of coral colonies or more commonly of related encrusting organisms red algae and foraminifers thus forming surface crusts slope microbialites generally form the ultimate stage of a biological succession indicating a deepening sequence whereby shallow water corals and associated encrusting organisms are replaced by deeper water assemblages of red algae and foraminifers before microbialite growth the precipitation of phosphatic iron manganese crusts and the deposition of planktonic micritic limestones on the microbialites characterize a deepening upward sequence the widespread development of microbialites in reef sequences from the last deglaciation characterizes a period of environmental degradation consequential on the rapid sea level rise and abrupt climatic changes of that time the reported biological succession reflects changes in water quality and especially an increase in nutrients in shallow water settings increased alkalinity and nutrient availability in interstitial waters were related to surface fluxes and terrestrial groundwater seepage while slope environments were exposed to continuous upwelling of nutrient rich deeper waters during the last deglacial sea level rise the age differences between corals and overlying slope microbialites range from 1600 to 8400 years based on high precision u series age measurements of both corals and microbialites and indicates that a significant time several thousand years elapsed between the development of the coralgal frameworks and the growth of slope microbialite crusts microbialites cannot be considered as part of the drowning event some 14 000 years ago that resulted in the demise of reef frameworks in the 90 110 m present depth range but are substantially younger

postglacial growth history of a french polynesian barrier reef tract tahiti central pacific bthe internal structure and growth pattern of tahiti reefs over the last 14 ka is reconstructed using sedimentological morphological and palaeobiological data coupled with radiometric dates in drill cores through the modern barrier reef flooding of the volcaniclastic deposits or the karst surface of a pleistocene reef started at 14 ka bp and coral growth began shortly after inundation the sequence in the tahiti barrier reef edge has formed predominantly through long term keep up growth controlled by stable environmental conditions while the adjacent backreef deposits did not start to accumulate before sea level stabilization around 6 ka the dominance of porites communities and the coeval occurrence of branching gracile lithophyllum in the lowermost part of the postglacial reef sequence 14 11 ka suggest the prevalence of uniformly moderate to low energy conditions and or growth in slightly deeper waters all over the drflled area during the early reef stages during the last 11 ka the reef frameworks developed in a high energy environment at maximum water depths of 5 6 m and were dominated by an acropora robusta danaihydrolithon onkodes association the local interlayering of other coralgal assemblages dominated by tabular acropora or domal porites reflects distinct diversification stages resulting either from the palaeotopographic control of the substrate or from slight and episodic environmental changes

coralgal composition of drowned carbonate platforms in the huon gulf papua new guinea implications for lowstand reef development and drowning abstract collision between the south bismarck plate and the northern edge of the australian plate has produced an actively subsiding foreland basin in the western huon gulf a series of drowned carbonate platforms and pinnacles are preserved on this margin due to a combination of this rapid subsidence and eustatic sea level changes over the last 450 ka we analyzed sedimentary and coralgal data from the platforms to better understand lowstand reef development and drowning in the huon gulf the recovered limestones are divided into five main sedimentary facies coral reef coralline foraminiferal nodule coralline foraminiferal crust halimeda and planktonic foraminiferal limestones based on a comparison with modern analogues in the indo pacific and elsewhere we identified coral reef deep fore reef slope deeper fore reef slope and pelagic hemipelagic paleoenvironmental settings an analysis of facies relationships and their paleoenvironmental meanings revealed lowstand corals reefs preserved at the top of the platforms that grew within 10 m of sea level two different coral assemblages were identified within this facies 1 a shallow high energy reef community characteristic of windward margins and limited to the deep platforms 1947 2121 2393 m and 2 another shallow community but indicative of more moderate lower energy reef conditions and limited to the middle 1113 1217 1612 m and shallow platforms 823 m the change from high to lower energy reef growth conditions suggests that oceanographic climatic conditions in the huon gulf have changed substantially through time primarily through the closure of the gulf as a result of tectonic rotation and uplift of the huon peninsula over the last 450 ka despite major environmental perturbations i e relative sea level and temperature changes the platforms and the shallow water coral reefs exposed at the top have been able to re establish themselves time and time again over the last 450 ka we also identified two different incipient drowning scenarios influenced by the rate of relative sea level rise more rapid drowning in the middle and deep platforms produced a thin veneer of coralline foraminiferal nodule and halimeda limestones over the shallow coral reef material while the slower drowning experienced by the shallowest platforms allowed thick coralline foraminiferal crust limestones to develop we recognize three main stages of platform development 1 initiation and growth characterized by shallow coral reef growth as the platforms grew close to sea level during the lowstands 2 incipient drowning marked by a shift to coralline foraminiferal nodule crust and halimeda limestones as the platforms began to drown during rapid eustatic sea level rise and continued subsidence and 3 the complete drowning of the platforms characterized by platform turn off increased bioerosion fe mn precipitation and pelagic hemipelagic sedimentation as the platform surfaces finally drop below the photic zone

deglacial mesophotic reef demise on the great barrier reef abstract submerged reefs are important recorders of palaeo environments and sea level change and provide a substrate for modern mesophotic deep water light dependent coral communities mesophotic reefs are rarely if ever described from the fossil record and nothing is known of their long term record on great barrier reef gbr sedimentological and palaeo ecological analyses coupled with 67 14c ams and u th radiometric dates from dredged coral algae and bryozoan specimens recovered from depths of 45 to 130 m reveal two distinct generations of fossil mesophotic coral community development on the submerged shelf edge reefs of the gbr they occurred from 13 to 10 ka and 8 ka to present we identified eleven sedimentary facies representing both autochthonous in situ and allochthonous detrital genesis and their palaeo environmental settings have been interpreted based on their sedimentological characteristics biological assemblages and the distribution of similar modern biota within the dredges facies on the shelf edge represent deep sedimentary environments primarily forereef slope and open platform settings in palaeo water depths of 45 95 m two coral algal assemblages and one non coral encruster assemblage were identified 1 massive and tabular corals including porites montipora and faviids associated with lithophylloids and minor mastophoroids 2 platy and encrusting corals including porites montipora and pachyseris associated with melobesioids and sporolithon and 3 melobesiods and sporolithon with acervulinids foraminifera and bryozoans based on their modern occurrence on the gbr and coral sea and modern specimens collected in dredges these are interpreted as representing palaeo water depths of 100 m respectively the first mesophotic generation developed at modern depths of 85 130 m from 13 to 10 2 ka and exhibit a deepening succession of 100 m palaeo water depth through time the second generation developed at depths of 45 70 m on the shelf edge from 7 8 ka to present and exhibit stable environmental conditions through time the apparent hiatus that interrupted the mesophotic coral communities coincided with the timing of modern reef initiation on the gbr as well as a wide spread flux of siliciclastic sediments from the shelf to the basin for the first time we have observed the response of mesophotic reef communities to millennial scale environmental perturbations within the context of global sea level rise and environmental changes

late quaternary evolution of ashtamudi sasthamkotta lake systems of kerala south west india abstract sedimentological and palynological analysis of two borehole samples collected from the confluence of kallada river with the ashtamudi lake in the south west coast of india have been addressed while ascertaining the late quaternary evolution of the two borehole samples the one collected from pangod 9 03 n 76 42 e reveals a fining upward sequence with medium to coarse sand 3 05 m at base organic carbon rich silt and fine sand dominated sediments 2 m at the middle and yellowish brown muddy sediments 3 2 m at the top the middle layer embeds a suite of partly carbonized sub fossil logs of wet evergreen to semi evergreen vegetation the palynoflora of this layer reveals that the depositional site is within the tidal limit and deposition occurred under high precipitation and atmospheric humidity the similarity in 14 c dates of a wood at 5 m bgl 7490 90 yrs bp and the embedding sediments 7480 80 yrs bp indicate quick burial of the riparian vegetation the west kallada borehole 9 30 n 76 37 e reveals middle to late holocene sequence of clayey silt 6250 110 yrs bp 3880 80 yrs bp and sand resting unconformably over greyish white clayey sand with pebbles and granules derived from laterite provenance palynological analysis shows that the holocene sedimentation took place under marine nearly marine environment and later changed to brackish water and finally to freshwater environment marine transgression 6000 yrs bp coupled with heavy rainfall in the hinterlands was responsible for faster sedimentation in the region the heavy mineral contents especially opaques garnet and sillimanite in the sediment samples of the study area as well as the bathymetric configuration of the ashtamudi sasthamkotta and chelupola lakes reiterate the fact that these lakes have been evolved from an embayment consequent to incomplete partial silting up during early to middle holocene higher sea levels and also under high rainfall of the holocene climatic optimum of around 10 000 7000 yrs bp

reef sedimentary accretion model reefsam understanding coral reef evolution on holocene time scales using 3d stratigraphic forward modelling abstract a detailed understanding of the development of coral reefs and their internal structure has important applications for predicting future reef trajectories in light of climate changes petroleum exploration and reconstructing past environmental changes such as sea level numerical computer modelling provides a quantitative means of testing and understanding reef processes and better predicting past and future reef development however most existing carbonate stratigraphic forward models sfms focus on the platform scale and several limitations in their simulation of important reef processes and reef scale features e g patch reefs sand aprons have been previously identified we present the reef sedimentary accretion model reefsam a new carbonate sfm designed to test new approaches to modelling processes important at the reef scale with the goal of better simulating reef features and evolution at higher temporal and spatial resolutions specific developments include a sediment transport model which calculates deposition based on a range of grain sizes additional controls on coralgal growth including wave energy and surface substrate specificity and model outputs showing categorized paleo conditions composition paleo depth and paleo energy along with numerous quantitative measures for objective comparison of model results to real world observational data which is often more abundant for modern holocene reefs than buried ancient reefs simulations of the well studied holocene one tree reef otr in the southern great barrier reef gbr showed improvements upon previous modelling attempts in both quantitative measures e g lagoon size or reef sea level catch up time and the ability to produce more realistic reef scale morphological features e g lagoonal patch reefs mostly sand filled lagoon and reef development characteristics e g transition from mostly vertical aggradation during sea level catch up to horizontal progradation afterwards controls on reef maturity lagoonal filling identified in previous modelling experiments were corroborated sensitivity testing also revealed a very high sensitivity to reef drowning these results indicate the new modelling approaches are viable and provide a way forward for future holocene reef evolution model development

high energy coralgal stromatolite frameworks from holocene reefs tahiti french polynesia drill cores from holocene reefs on tahiti french polynesia reveal a framework composed of massive branching acroporids encrusted by coralline algae associated with sessile vermetid gastropods and arborescent foraminifers laminated micritic crusts form coatings over coral branches or more commonly over related encrusting organisms throughout the cored reef sections these crusts appear as a major structural and volumetric component of the reef framework the microbial nature of these micritic crusts is inferred from their typical organic growth forms and geometry the occurrence of microbial remains and stable isotope measurements the reef communities accumulated at depths less than 5 m below mean sea level in a high energy environment throughout vertical growth from 7140 170 yr bp to the present the nature of the involved benthic communities stable isotope data and high calcification rates of microbially encrusted corals strongly suggest that local environmental conditions have been optimal for reef development for the last 7000 years the causes of the predominance of microbial communities over actual encrusters red algae foraminifers remain problematic and could be related to short term fluctuations in ecological parameters microbial micritic crusts seemingly played a prominent role in protecting the coralgal colonies from bioeroders and grazers and possibly in strengthening the framework due to rapid lithification the record of similar microbial crusts in other quaternary reef tracts suggests that microbial communities may have played a more prominent role in quaternary reefs than presently recognized

holocene sea level determination relative to the australian continent u th tims and 14c ams dating of coral cores from the abrolhos islands u th tims and 14 c ams measurements are presented from two coral cores from the easter group of the houtman abrolhos islands between 28 s and 29 s on the western continental margin of australia the u th measurements on the morley core from morley island cover a depth interval from 0 2 m above present sea level to 24 4 m below present sea level and comprise eleven samples the ages vary between 6320 50 a at 0 2 m above sea level and 9809 95 a at 24 4 m below sea level all errors are 2 the mean growth rate is 7 1 0 9 m ka the 14 c dates of selected morley core corals show that the 14 c ages are 1000 a younger than their corresponding u th ages which agrees with previous results the main purpose of our 14 c measurements is to be able to compare them precisely with other coral cores where no u th measurements are available the u th measurements of the suomi core from suomi island cover a depth interval from 0 05 m to 14 2 m below present sea level and consist of four samples the ages vary between 4671 40 a at 0 05 m below sea level and 7102 82 a at 14 2 m below sea level with a mean growth rate of 5 8 0 2 m ka the growth history of both cores is explained by a simple model in which the growth rates of the morley core can be interpreted as reflecting local rates of sea level rise whereas the suomi core is interpreted as reflecting lateral growth during the past 6000 a our results indicate that sea level relative to the western margins of the australian continent was about 24 m lower than present at about 9800 a b p 14 c gives a date of 8500 a b p sea level then rose and reached a highstand slightly higher than the present position at about 6300 a b p 14c date 5500 a this highstand declined but was still higher than present at 4600 a b p this is in agreement with previous observations along the australian coastal margins and with observations from the huon peninsula papua new guinea our results are very similar to theoretical numerical models which take into consideration water loading and isostatic compensation and viscous mantle flow in contrast coral cores from barbados show that corals with a 14 c age of 5500 a b p are some 10 m b p s l we interpret the difference between the barbados core and the morley core as resulting from additional flooding of barbados by water redistribution due to changes in the earth s geoid but not reflecting global sea level rise or major addition of melt waters over the past 6000 a the difference in the geoid at barbados between 6000 a b p and the present will require a refinement in the geophysical models precise 230 th tims measurements on continental coasts will be required to provide an adequate data base for modelling deformation flow of mantle material and sea level height

the great barrier reef the chronological record from a new borehole abstract a new borehole 210 mbsf meters below sea floor deep drilled in ribbon reef 5 on the great barrier reef off cooktown ne australia reveals a shallowing upwards succession the younger part of which is punctuated by a series of erosion surfaces nine depositional units have been defined by lithological changes and are numbered sequentially from the base of the hole upwards aminostratigraphy magnetostratigraphy radiocarbon dating uranium series dating and modeling together with strontium ratios have been applied in an attempt to establish a chronology of accumulation carbonate deposition began about 770 ka ago in a relatively deep water slope environment and is represented by a series of debris flows lithoclasts within these rocks indicate that older limestones already existed in the area subsequent accretion involved the downslope accumulation of grainstones and wackestones sometimes cross laminated characterized by intervals with abundant rhodoliths and scattered probably reworked corals four units at the base of the hole reflect deposition that probably began during isotope stage 16 and continued through stage 15 from about 770 to about 564 ka unit 5 probably extended to stage 11 about 400 ka and unit 6 to stage 9 330 ka typical reefal associations of corals and calcareous algae were established in this area only above depths of about 100 m in the borehole units 5 4 the succession is apparently unbroken to an erosion surface at 36 mbsf indicating subaerial emergence the lack of evidence of emergence below this surface reflects progressive accretion or progradation or both two younger erosion surfaces define further periods of lowered sea level unit 7 is attributed to deposition during isotope stage 7 but erosion during stage 8 resulted in the preservation of only 8 m of unit 7 limestones unit 8 is correlated with stage 5 125 ka and unit 9 is interpreted as holocene post 7 700 ka the limited thicknesses of units 7 8 and 9 are considered to reflect erosion the progressive shallowing brought the depositional surface within the zone exposed during lowstands and there is no sedimentological evidence that aggradation was restricted by a lack of accommodation

nature and biological composition of the new caledonian outer barrier reef slopes the grande terre of new caledonia is enclosed by one of the longest barrier reefs in the world for the first time the fore reef slopes of this barrier reef have been sampled by dredging from 40 to 320 m deep in order to analyze their sedimentological and biological characteristics the rocks and sediments can be divided into seven sedimentary facies bindstones dominated by coralline algal crusts bindstones dominated by foraminiferal crusts bindstones dominated by bryozoan crusts coral framestones bindstones and interstratified packstones rich in skeletal debris packstones wackestones and grainstones rich in rock gravels radiocarbon dating performed on encrusting organisms coralline algae and acervulinids and corals provide ages relatively young these ages confirm that the encrusting organisms are modern and the corals mainly dated of holocene are reworked due to the instability of the fore reef slopes especially during storms because the biological assemblages are distributed according to a bathymetric range depending on light intensity a model of distribution of modern encrusting calcareous organisms can be proposed from our observations and analyses from the upper reef slopes to approximately 90 m thick coralline algal crusts are dominant and distributed in three groups group c the shallowest parts of the fore slopes is mainly characterized by mastophorids hydrolithon reinboldii h cf munitum lithoporella melobesoides aethesolithon cf problematicum neogoniolithon sp and undetermined species and lithophylloids lithophyllum sp l pustulatum group b composed of lithophylloids lithophyllum sp l cf kotschyanum l cf moluccence l pustulatum mesophyllum sp and peyssonnelia sp occurs from 15 to 40 m group a rich in mesophyllum sp m cf mesomorphum peyssonnelia sp and sporolithon sp is characteristic of deep reef slopes up to 90 m below approximately 90 m when the light intensity decreases the encrusting foraminifera acervulinids progressively replace the coralline algal crusts such a model is particularly useful to interpret and reconstruct the past quaternary reef environments rich in crusts of coralline algae and or foraminifera

coral reef response to quaternary sea level and environmental changes state of the science there is considerable uncertainty about future sea level projections due to the current poor understanding of the vulnerability and sensitivity of ice sheets to global warming fossil coral reefs represent a unique archive of sea level and associated environmental changes that extend far beyond instrumental records here recent advances in this field are summarized focusing on periods of earth history typified by rapid sea level rise and short term climate excursions sea level and reef response records from the last deglaciation and periods characterized by higher sea level stands and short term and low magnitude sea level oscillations such as the mid to late holocene and the last interglacial are synthesised special emphasis is given to understanding how coral reefs have responded to these changes in terms of reef development architecture and composition finally seven major challenges and future research directions are identified

calibration of the c 14 timescale over the past 30 000 years using mass spectrometric u th ages from barbados corals uranium thorium ages obtained by mass spectrometry from corals raised off the island of barbados confirm the high precision of this technique over at least the past 30 000 years comparison of the u th ages with 14c ages obtained on the holocene samples shows that the u th ages are accurate because they accord with the dendrochronological calibration before 9 000 yr bp the 14c ages are systematically younger than the u th ages with a maximum difference of 3 500 yr at 20 000 yrbp the u th technique thus provides a way of calibrating the radiocarbon timescale beyond the range of dendrochronological calibration

revisiting the quaternary development history of the western new caledonian shelf system from ramp to barrier reef abstract the present paper is based on the study of a new core tenia 3 151 20 m long and revisitation of previous core data from the western new caledonian barrier reef based on variations in lithology and stable isotope signatures and the occurrence of unconformity surfaces the tenia 3 sequence is subdivided into ten units regarded as deposited during interglacial high sea levels five detrital and two framework facies are delineated using their biological and textural attributes including coral growth forms and assemblages these facies are interpreted as representative of outer to inner carbonate shelf ramp to barrier reef environments variations in the facies within each stratigraphic unit occur mainly as vertical transitions from lower energy and probably deeper to higher energy probably shallower settings the succession of depositional events is reconstructed using all available age criteria including lithostratigraphy magnetostratigraphy uranium series dating and nannofossil biostratigraphy shallow water coral communities appear to have been developed as soon as carbonate deposition started at around 1 2 million years ma but the initiation of typical coral reef tracts is likely to have occurred not prior to 0 40 million years during marine isotope stage mis 11 carbonate deposition previous to mis 11 is considered to have operated along an open shelf margin i e a ramp or non rimmed platform based on the re examination of the core dataset previously acquired from the new caledonian reefs the coral communities dominated by massive forms mainly poritids are assumed to have remained stable in composition over the past 1 4 ma similarly as indicated by a preliminary study of pollen assemblages in the core the composition of terrestrial flora dominated by podocarpaceae and araucariaceae has not apparently suffered significant change over the past 1 ma and reflects climate conditions cooler and drier than today mean subsidence rates are derived tentatively over the past 1 ma from the stratigraphic position at present reached by the top of depositional units mean rates of 0 08 mm yr 1 for the western new caledonian margin are consistent with past sea level estimates the quaternary depositional history of the new caledonian shelf margin appears to have been controlled by both the amplitude of sea level changes and by differing vertical tectonic movements comparison between the depositional shelf histories from western new caledonia north eastern australia southern belize and the ryukyu islands supports the assumption that coral populations over the early and mid pleistocene developed as non reefal communities along ramp systems not forming continuous outer shelf reef rims at a global scale quaternary reef rimmed platforms are likely to have initiated after the mid pleistocene climate transition from marine isotope stage 11 at about 0 4 ma

holocene reef development where wave energy reduces accommodaton space kailua bay windward oahu hawaii u s a abstract analyses of 32 drill cores obtained from the windward reef of kailua bay oahu hawaii indicate that high wave energy significantly reduced accommodation space for reef development in the holocene and produced variable architecture because of the combined influence of sea level history and wave exposure over a complex antecedent topography a paleostream valley within the late pleistocene insular limestone shelf provided accommodation space for more than 11 m of vertical accretion since sea level flooded the bay 8000 yr bp virtually no net accretion 6 m coral framestone accreted at rates of 2 5 6 0 mm yr in water depths 11 m during the early holocene it abruptly terminated at 4500 yr bp because of wave scour as sea level stabilized more than 4 m of rudstone derived from the upper fore reef accreted at depths of 6 to 13 m below sea level between 4000 and 1500 yr bp coincident with late holocene relative sea level fall variations in the thickness composition and age of these reef facies across spatial scales of 10 1000 m within kailua bay illustrate the importance of antecedent topography and wave related stress in reducing accommodation space for reef development set by sea level although accommodation space of 6 to 17 m has existed through most of the holocene the kailua reef has been unable to catch up to sea level because of persistent high wave stress

new constraints on the origin of the australian great barrier reef results from an international project of deep coring two new boreholes provide the first direct evidence of the age of the australian great barrier reef an inner shelf sequence total depth 86 m basal age 210 40 ka comprises a dominantly siliciclastic unit thickness 52 86 m overlain by four carbonate units total thickness 0 34 m a shelf edge and slope sequence total depth 210 m reveals three major sections 1 a lower section of resedimented flows deposited on a lower slope 2 a mid section including intervals of corals rhodoliths and calcarenites with low angle graded laminae and 3 an upper section of four shelf margin coral reef units separated by karst surfaces bearing paleosols sr isotope and magnetostratigraphic data indicate that the central great barrier reef is relatively young post bruhnes matuyama boundary time and our best estimate for the onset of reef growth on the outer barrier system is ca 600 280 ka this date suggests that reef initiation may have been related to the onset of full eccentricity dominated glacio eustatic sea level oscillation as inferred from large amplitude saw tooth 100 k y 18o cycles after marine isotope stage 17 rather than to some regional environmental parameter a major question raised by our study is whether reef margins globally display a similar growth history the possibility of a global reef initiation event has important implications for basin to shelf partitioning of caco3 atmospheric carbon dioxide levels and global temperature change during quaternary time

holocene coral reef terraces and coseismic uplift of huon peninsula papua new guinea abstract as many as six levels of emerged holocene coral terraces occur along 40 km of coastline on the huon peninsula papua new guinea recording uplift history since culmination of the postglacial transgression the holocene reef crest ca 6000 yr b p is tilted down to the northwest parallel to the coast and concordant with the deformation of the last interglacial coral reef terrace and descends from 23 to 12 m in the study area the pattern and rate of deformation have been uniform in the late quaternary because average uplift rates have remained the same since the last interglaciation the holocene terraces described here are erosional features with regressive encrusting corals developed upon the holocene transgressive reef the multiple levels represent episodic probably coseismic uplift which has occurred repeatedly in the last ca 6000 yr significant longshore variation in the age of the lowest terrace from 1700 to 2500 yr b p suggests independent coseismic uplift on different sectors of the coast this is supported by age height relationships of the higher holocene terraces nonlinear uplift during the holocene with recurrence intervals increasing toward the present is clearly recorded by the regressive terraces in each subregion some of the holocene regressive terraces grade laterally into fluvial terraces capped with debris flow deposits probably reflecting seismically triggered mass movement

raised coral terraces at malakula vanuatu southwest pacific indicate high sea level during marine isotope stage 3 the occurrence of a series of raised coral reefs from the uplifted island of malakula vanuatu sw pacific provide an opportunity to examine sea level fluctuations over at least the past 120 000 years thirteen fossil coral samples from malakula were analyzed by the thermal ionization mass spectrometry tims u th dating technique yielding information on sea levels during late marine isotope stage 3 and early stage 4 our findings are in good agreement with sea level estimates from raised coral terraces in papua new guinea and the recent sea level reconstruction from the deep sea sedimentary 18o records in particular our coral data appear to confirm that sea levels at about 45 000 50 000 yr b p were only 30 to 60 m below the present level combined with other evidence of sea level change our data provide a strong case for much higher sea levels and therefore markedly reduced continental ice volume at 47 000 to 49 000 years ago

a large drop in atmospheric 14c 12c and reduced melting in the younger dryas documented with 230th ages of corals paired carbon 14 14 c and thorium 230 230 th ages were determined on fossil corals from the huon peninsula papua new guinea the ages were used to calibrate part of the 14 c time scale and to estimate rates of sea level rise during the last deglaciation an abrupt offset between the 14 c and 230 th ages suggests that the atmospheric 14 c 12 c ratio dropped by 15 percent during the latter part of and after the younger dryas yd this prominent drop coincides with greatly reduced rates of sea level rise reduction of melting because of cooler conditions during the yd may have caused an increase in the rate of ocean ventilation which caused the atmospheric 14 c 12 c ratio to fall the record of sea level rise also shows that globally averaged rates of melting were relatively high at the beginning of the yd thus these measurements satisfy one of the conditions required by the hypothesis that the diversion of meltwater from the mississippi to the st lawrence river triggered the yd event

late quaternary barrier and fringing reef development of bora bora society islands south pacific first subsurface data from the darwin type barrier reef system the universally known subsidence theory of darwin based on bora bora as a model was developed without information from the subsurface to evaluate the influence of environmental factors on reef development two traverses with three cores each on the barrier and the fringing reefs of bora bora were drilled and 34 uranium series dates obtained and subsequently analysed sea level rise and to a lesser degree subsidence were crucial for holocene reef development in that they have created accommodation space and controlled reef architecture antecedent topography played a role as well because the holocene barrier reef is located on a pleistocene barrier reef forming a topographic high the pedestal of the fringing reef was pleistocene soil and basalt barrier and fringing reefs developed contemporaneously during the holocene the occurrence of five coralgal assemblages indicates an upcore increase in wave energy age depth plots suggest that barrier and fringing reefs have prograded during the holocene the holocene fringing reef is up to 20 m thick and comprises coralgal and microbial reef sections and abundant unconsolidated sediment fringing reef growth started 8780 50 yr bp accretion rates average 5 65 m kyr 1 the barrier reef consists of 30 m thick holocene coralgal and microbial successions holocene barrier reef growth began 10 030 50 yr bp and accretion rates average 6 15 m kyr 1 the underlying pleistocene reef formed 116 900 1100 yr bp i e during marine isotope stage 5e based on pleistocene age depth and coralgal palaeobathymetry the subsidence rate of bora bora was estimated to be 0 05 to 0 14 m kyr 1 in addition to subsidence reef development on shorter timescales like in the late pleistocene and holocene has been driven by glacioeustatic sea level changes causing alternations of periods of flooding and subaerial exposure comparisons with other oceanic barrier reef systems in tahiti and mayotte exhibit more differences than similarities

microborer ichnocoenoses in quaternary corals from new caledonia reconstructions of paleo water depths and reef growth strategies in relation to environmental changes abstract coral reef growth and development depend on several environmental factors including tectonic and climatic parameters and local ecological drivers reef growth is especially sensitive to sea level variations paleo water depth reconstructions are essential tools used to determine reef growth patterns during different periods of reef growth assemblages of corals and or coralline algae have been commonly used in such paleodepth reconstructions this study shows that using microendolith ichnocoenoses can sometimes provide better accuracy than traditional coralgal analyses particularly in the depth range 0 10 m where coralgal assemblages usually show broad distribution ranges holocene and pleistocene cores from two barrier reef sites on the west coast of grande terre in new caledonia are examined here holocene reef development at these sites feature examples of microendolith ichnocoenoses that document rapid environmental changes and small sea level variations of about 2 5 m in amplitude and record these changes with more accuracy than coral and coralline algae assemblages which are highly dependant on the hydrodynamic energy of the setting during the pleistocene which was less chronologically constrained the microendolith ichnocoenoses also reflect paleo water depths and reef growth patterns at different periods of reef history

new evidence of hawaiian coral reef drowning in response to meltwater pulse 1a abstract fossil coral reefs are valuable recorders of glacio eustatic sea level changes as they provide key temporal information on deglacial meltwater pulses mwps the timing rate magnitude and meltwater source of these sea level episodes remain controversial despite their importance for understanding ocean ice sheet dynamics during periods of abrupt climatic change this study revisits the west coast of the big island of hawaii to investigate the timing of the 150 m h1d terrace drowning off kawaihae in response to mwp 1a we present eight new calibrated 14c ams ages which constrain the timing of terrace drowning to at or after 14 75 0 33 0 42 kyr bp coeval with the age of reef drowning at kealakekua bay u th age 14 72 0 10 kyr bp 70 kms south along the west coast integrating the chronology with high resolution bathymetry and backscatter data detailed sedimentological analysis and paleoenvironmental interpretation we conclude the h1d terrace drowned at the same time along the west coast of hawaii in response to mwp 1a the timing of h1d reef drowning is within the reported uncertainty of the timing of mwp 1a interpreted from the iodp expedition 310 tahitian reef record

episodic reef growth in the granitic seychelles during the last interglacial implications for polar ice sheet dynamics abstract we present a detailed taxonomic and lithologic analysis of fossil reefs in the granitic seychelles to improve constraints on global mean sea level behavior during the last interglacial sea level highstand 129 000 116 000 years ago in particular we have assessed the coralgal reef outcrops for any sedimentalogic evidence of sub orbital sea level oscillations that may have occurred during this warm interglacial period at the outcrop scale we observe at least three distinct episodes of reef growth punctuated by two discontinuities that typically manifest as coral rubble layers or extensive lateral encrustations of the hydrozoan coral millepora exaesa hiatuses in reef growth at other sites around the world have been interpreted as relative sea level falls and or environmental disturbances we have tested the hypothesis that these discontinuities that we refer to as disturbance horizons are related to ephemeral drops in sea level that have been inferred at last interglacial reef sites from other sites around the globe at two sites there is sedimentological evidence in the form of extensive dissolution and freshwater cements associated with the disturbance horizons that would require subaerial exposure followed by marine inundation at the remaining sites evidence is consistent with but not necessarily indicative of an ephemeral drop in sea level to establish if these disturbance horizons are coeval between the outcrops and if they are local or global features requires high precision dating of the disturbance horizons along with a critical analysis of sedimentary and chronological evidence from other sites around the globe if the disturbance horizons observed in the seychelles represent transient sea level falls or still stands during the last interglacial this would imply a dynamic behavior of the polar ice sheets during this past warm period

heterozoan carbonates when where and why a synthesis on parameters controlling carbonate production and occurrences abstract in modern and phanerozoic times heterozoan carbonates group a large array of depositional environments from the poles to the tropics this global assessment reviews the critical parameters and controlling factors of heterozoan carbonates i stratigraphic and global distributional trends ii oceanographic and trophic relationships and iii biological and sedimentary processes well documented case studies n 129 have been investigated when facies and stratigraphic attributes were available and when environmental settings such as oceanography climate and paleogeography were clearly identified these case studies occur during specific periods of time in the sedimentary record e g late ordovician early carboniferous early permian and neogene while they are absent during others e g triassic and jurassic periods during greenhouse to icehouse transitions and those with active thermohaline circulation are particularly conducive for heterozoan carbonates based on global oceanographic patterns and existing ecological and hydrodynamic regime classifications hallock 2001 pedley and carannante 2006 james and jones 2015 a process based classification scheme is proposed that distinguishes two main heterozoan carbonate systems i a highly productive system characterized by suspension feeding biota and ii an oligo mesotrophic warm temperate system characterized by red algal and seagrass derived biota eight depositional models are proposed that combine i the source of energy for metabolic activities that allow the carbonate producing biota to thrive and ii hydrodynamics and physiography of the depositional system that control the sediment accumulation the local and platform scale based profiles can be used to complement the facies approach of james and jones 2015

continuous record of reef growth over the past 14 k y on the mid pacific island of tahiti two boreholes were drilled through coralgal sequences in the barrier reef edge of the mid pacific island of tahiti and their bases were radiometrically dated at 10 23 0 05 and 13 77 0 05 ka thousand calendar years the sequences are composed mainly of the reef edge acropora gr danai robusta and hydrolithon onkodes assemblage occasionally replaced by reef slope tabular acropora neogoniolithon or domal porites lithophyllum assemblages the response of reef growth to sea level rise has varied according to the framework type and vertical accretion rates have ranged from 9 3 to 20 6 mm yr 1 from a general trend of long term continuous sea level rise tracked by growth the reef edge coralgal assemblages have experienced two distinct changes controlled by the antecedent paleotopography and internal reef processes during the past 13 8 k y at tahiti there is no evidence of any reef drowning event primarily caused by global glacio eustatic perturbations as has been recorded in the caribbean

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

reef coralgal assemblages as recorders of paleobathymetry and sea level changes in the indo pacific province the coralgal framework within the outer reef margin of many indo pacific reefs exhibits three main shallow water communities the environmental significance of which can be inferred by comparison with their modern counterparts a community dominated by tabular acropora gr hyacinthus cytherea with branching pocillopora damicornis p eydouxi montipora digitata occasional domal faviids and mm thick crusts of the coralline algae lithophyllum and mesophyllum mainly typical of the 6 15 m paleodepth range a community including robust branching acropora gr danai robusta a humilis a digitifera and subordinate favia stelligera echinopora gemmacea associated to vermetid gastropods and thick coralline crusts of hydrolithon cf onkodes and neogoniolithon cf fosliei flourishing in depths less than 6 m in medium to high water energy settings a community composed of domal porites cf lutea and p cf lobata with occasional acropora gr danai robusta and cm thick crusts of coralline algae in sheltered habitats in depths less than 10 m these biological assemblages allow us to determine relationships between reef growth and paleobathymetry and consequently to reconstruct regional relative sea level curves high water energy reefal assemblages provide stronger evidence for reconstructing sea level curves than low energy buildups because they have generally been controlled by a keep up growth mode subsiding reef sites seem to be more reliable indicators of sea level variations because they usually present expanded reef sequences

stromatolites associated with coralgal communities in holocene high energy reefs thick laminar to columnar stromatolitic growths encrust typical high energy coralgal reef communities in a french polynesian outer reef edge the reef communities accumulated during vertical growth from 5870 100 yr b p to the present at depths never exceeding 5 m below mean sea level oxygen and carbon isotope records and high calcification rates of stromatolite encrusted corals strongly suggest that for about the past 6000 yr the local environmental conditions were optimal for reef development accordingly stromatolites can grow in healthy holocene reefs because similar stromatolites have been recorded in other cenozoic reefs we suggest that microbial structures may have played a more prominent role in cenozoic reef growth than is currently recognized

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

timing and warmth of the last interglacial period new u series evidence from hawaii and bermuda and a new fossil compilation for north america abstract the timing and duration of the last interglacial period have been controversial with some studies suggesting a relatively short duration that is orbitally forced and others suggesting a long duration that is at most only partly related to orbital forcing new high precison thermal ionization mass spectrometric tims u series ages of last interglacial corals from hawaii and bermuda test these competing hypotheses waimanalo formation corals from slowly uplifting oahu hawaii range in age from 134 to 113 ka with most ages between 125 and 115 ka combined with published u series ages from nearby lanai the data suggest a long last interglacial period that may have occurred from 136 to at least 115 ka the results indicate that orbital forcing may not have been the only control on ice sheet growth and decay because sea level would have been high at times of relatively low northern hemisphere summer insolation on tectonically stable bermuda deposits from the 200 ka penultimate interglacial period 120 ka peak last interglacial period and 80 ka late last interglacial period high sea stands have been newly dated fossil corals on bermuda are derived from patch reefs that likely were catch up responses to sea level rise it is expected that u series ages of last interglacial corals on bermuda should overlap with but not be as old as the range of corals on oahu last interglacial corals on bermuda give a range of 125 113 ka which supports this hypothesis a large number of emergent marine deposits on hawaii bermuda and along coastal north america have now been dated to the last interglacial period both oahu and bermuda have marine invertebrate faunas with a number of extralimital southern species of mollusks suggesting warmer than present waters during the last interglacial period warmer waters are also suggested for last interglacial localities around most of north america from florida to canada and greenland and baja california to alaska these observations are consistent with similar warm water faunas of last interglacial age reported from japan the mediterranean basin and western australia it is likely that significant changes in ocean currents took place during the last interglacial period with a movement of relatively warm waters to higher latitudes than is the case today

holocene reef accretion southwest molokai hawaii u s a abstract two reef systems off south molokai hale o lono and hikauhi separated by only 10 km show strong and fundamental differences in modern ecosystem structure and holocene accretion history that reflect the influence of wave induced near bed shear stresses on reef development in hawaii both sites are exposed to similar impacts from south kona and trade wind swell however the hale o lono site is exposed to north swell and the hikuahi site is not as a result the reef at hale o lono records no late holocene net accretion while the reef at hikauhi records consistent and robust accretion over late holocene time analysis and dating of 24 cores from hale o lono and hikauhi reveal the presence of five major lithofacies that reflect paleo environmental conditions in order of decreasing depositional energy they are 1 coral algal bindstone 2 mixed skeletal rudstone 3 massive coral framestone 4 unconsolidated floatstone and 5 branching coral framestone bafflestone at hale o lono 10 cores document a backstepping reef ranging from 8 100 cal yr bp offshore to 4 800 cal yr bp nearshore a depauperate community of modern coral diminishes shoreward and seaward of 15 m depth due to wave energy disrupted recruitment activities and physical abrasion evidence suggests a change from conditions conducive to accretion during the early holocene to conditions detrimental to accretion in the late holocene reef structure at hikauhi reconstructed from 14 cores reveals a thick rapidly accreting and young reef maximum age 900 cal yr bp living coral cover on this reef increases seaward with distance from the reef crest but terminates at a depth of 20 m where the reef ends in a large sand field the primary limitation on vertical reef growth is accommodation space under wave base not recruitment activities or energy conditions interpretations of cored lithofacies suggest that modern reef growth on the southwest corner of molokai and by extension across hawaii in general is controlled by wave induced near bed shear stress related to refracted north pacific swell holocene accretion patterns here also reflect the long term influence of wave induced near bed shear stress from north swell during late holocene time this finding is consistent with other studies e g grigg 1998 cabioch et al 1999 that reflect the dominance of swell energy and sea level in controlling modern and late holocene accretion elsewhere in hawaii and across the pacific and indian oceans notably however this result is refined and clarified for hawaii in the hypothesis of rooney et al 2003 stating that enhancement of the el nino southern oscillation beginning approximately 5000 years ago led to increased north swell energy and signaled the end to net accretion along exposed coastlines in hawaii the exposure of hale o lono to north swell and the age of sea floor there ca 4 800 cal yr bp coupled with the lack of north swell incidence at hikauhi and the continuous accretion that has occurred there over the last millennium strongly supports the enso reef hypothesis as outlined by rooney et al 2003 other factors controlling holocene reef accretion at the study site are relative sea level position and rate of rise and wave sheltering by laau point habitat suitable for reef accretion on the southwest shore of molokai has shrunk throughout the holocene

coral reefs and sea level change abstract coral reefs provide significant evidence for former sea level positions because of their geological preservation and suitability for dating interpretation of this evidence presumes an understanding of reef geomorphology modern reef organism distributions and environmental factors influencing them fossil reef terraces formed during the last interglacial marine oxygen isotope mis substage 5e 128 116 ka are prevalent on many tropical shorelines and there has been ongoing debate as to the height reached by sea level during that highstand observations from numerous last interglacial sites suggest that sea level was at least 3 m above present sea level implying less extensive icesheets than at present an elevation of 6 m has commonly been adopted when correcting tectonically active sites for uplift recent compilations suggest elevations up to 8 9 m but incorporate few observations from reefs where the last interglacial is found below sea level oscillation of sea level during mis 5e has been interpreted from several sites with recent studies inferring rapid rise of several metres at the end of the interglacial these interpretations are at the limits to the precision with which corals can currently be dated and their palaeo water depths inferred it is not surprising that constraining last interglacial sea level changes within uncertainties of less than 1 2 m remains controversial considering sea level variations recognised between reef sites in the holocene and observed geographical variation in isostatic or flexural adjustments fossil coral reefs on uplifting margins also provide clear evidence for mis substages 5c and 5a and those on huon peninsula indicate fluctuations related to heinrich events mis 3 interpretations show considerable variability between sites with still greater uncertainties about sea level timing and elevation during previous interglacials future study of extensive sequences of fossil reefs preserved on rapidly subsiding margins could address these uncertainties submerged reefs have already yielded important information about sea level rise during the last deglaciation coring around barbados and tahiti as well as on the huon peninsula has produced a broadly consistent picture of ice melt reflecting eustatic change since the last glacial maximum these studies have shown the sensitivity of reefs to rapid sea level rise associated with meltwater pulses with some reefs drowning while others back stepped integrated ocean drilling program iodp expeditions to tahiti and recently the great barrier reef extended these records but details of timing nature and impact of deglacial meltwater pulses remain elusive studies of holocene reefs have indicated different growth strategies some kept up with sea level while others caught up when sea level decelerated holocene sea level appears to have experienced a gradual rise up to present across the caribbean providing accommodation space for reefs to accrete vertically whereas in the indo pacific sea level has been near its present level since 7 ka with many reef flats emergent following a slight fall of sea level caused by ocean siphoning microatolls on reef flats provide perhaps the clearest evidence of past sea level position but in their absence novel biological or other sea level indicators are required to better constrain palaeo water depths there is an urgent need for further research from additional key reef locations not only to decipher processes driving past sea level change and its geographical variability but also to better understand how coral reefs will respond in the context of future sea level rise

continuous reef growth during the last 23 cal kyr bp in a tectonically active zone vanuatu southwest pacific abstract at urelapa island vanuatu sea level rise and a tectonic uplift of 3 mm yr 1 have controlled water depth and the colonization and reef development on a substrate from 23 until 6 cal kyr bp analysis of coralgal assemblages offers insights on the mode of reef growth and on water depth over the reef for the studied period those assemblages precisely dated by the 230 th 234 u method give valuable information on the rate and timing of sea level rise since the last glacial maximum the urelapa reef sequences are characterized by upwards replacement of reef frameworks which indicates changes in wave energy through time the sudden acceleration of sea level rise associated with meltwater pulse 1b at around 11 3 cal kyr bp is marked by a change in reef growth strategy from a keep up mode to a catch up mode we examine the delay in timing of the occurrence of suitable substrates the role of paleoceanographic factors and the influence of possible jumps in sea level

reconciliation of late quaternary sea levels derived from coral terraces at huon peninsula with deep sea oxygen isotope records a major discrepancy between the late quaternary sea level changes derived from raised coral reef terraces at the huon peninsula in papua new guinea and from oxygen isotopes in deep sea cores is resolved the two methods agree closely from 120 ka to 80 ka and from 20 ka to 0 ka ka 1000 yr before present but between 70 and 30 ka the isotopic sea levels are 20 40 m lower than the huon peninsula sea levels derived in earlier studies new high precision u series age measurements and revised stratigraphic data for huon peninsula terraces aged between 30 and 70 ka now give similar sea levels to those based on deep sea oxygen isotope data planktonic and benthic 18o data using the sea level and deep sea isotopic data oxygen isotope ratios are calculated for the northern continental ice sheets through the last glacial cycle and are consistent with results from greenland ice cores the record of ice volume changes through the last glacial cycle now appears to be reasonably complete