holocene reef growth dynamics on kodakara island 29 n 129 e in the northwest pacific abstract the spatial distribution of modern coral reefs in the northwest pacific nwp is restricted to approximately 30 n understanding the high latitude reef growth process and its correlation to climate change may provide important insights into future reef growth at even higher latitudes in response to global warming we conducted field surveys and obtained seven cores from the raised reefs of kodakara island 29 n 129 e in the nwp to determine the changes in and response of reef growth dynamics to millennial scale climate change through the holocene to reconstruct the timing of the reef growth 37 coral ages were determined using accelerator mass spectrometry ams radiocarbon dating the island is characterized by three holocene reef terraces terraces i to iii which were uplifted ca 2 4 ka 1 0 0 4 ka and in the modern era three growth hiatuses occurred circa 5 9 5 8 ka 4 4 4 0 ka and 3 3 3 2 ka which correlate with millennial scale climate changes hamanaka et al 2012 the reef growth began at least 8 ka relatively rapid vertical growth of 3 6 3 3 m kyr 1 occurred between 8 and 6 ka the reef started growing near land and then gradually extended seaward the reef growth around the reef slope decelerated after 6 ka and most likely coincided with the first and second hiatuses detected landward in contrast with the reef flat which resumed its growth after the third hiatus event the reef mound accretion on the slope ceased definitively terrace i was uplifted ca 2 4 ka the reef growth reactivated ca 1 3 ka and the reef grew at a rate of 9 1 m kyr 1 between 1 3 and 1 0 ka this rate is the fastest growth recorded in this study this time interval corresponds to the medieval climatic anomaly mca the cause of the delayed reef growth between 2 4 and 1 4 ka remains unclear but it may imply the existence of a late holocene hiatus due to a weaker kuroshio current kc ca 1 7 ka and to strong el nino southern oscillation enso activity between 2 and 1 5 ka in the east pacific the timing of the hiatuses agrees with the weakening of the kc and the more frequent el nino events during the positive phase of the pacific decadal oscillation pdo whereas the rapid growth coincides with la nina conditions such as the mca during the negative phase of the pdo our results indicate that the climate event at approximately 4 ka caused the largest change in the reef growth and it may have affected reefs throughout the pacific region specifically the enso and pdo phases may have impacted the reef growth and kc behavior

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

insolation values for the climate of the last 10 million years new values for the astronomical parameters of the earth s orbit and rotation eccentricity obliquity and precession are proposed for paleoclimatic research related to the late miocene the pliocene and the quaternary they have been obtained from a numerical solution of the lagrangian system of the planetary point masses and from an analytical solution of the poisson equations of the earth moon system the analytical expansion allows the direct determination of the main frequencies with their phase and amplitude numerical and analytical comparisons with the former astronomical solution ber78 are performed so that the accuracy and the interval of time over which the new solution is valid can be estimated the corresponding insolation values have also been computed this analysis leads to the conclusion that the new values are expected to be reliable over the last 5 ma in the time domain and at least over the last 10 ma in the frequency domain

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

pleistocene reef development in the southwest ryukyu islands japan abstract calcareous nannofossil and sedimentological studies of the pleistocene ryukyu group based on 13 cores and surface outcrops on irabu jima and shimoji jima the ryukyu islands southwestern japan suggest that these sediments were deposited at 1 5 0 3 ma and unconformably overlie the pliocene shimajiri group the ryukyu group consists mainly of reef complex deposits which accumulated in a wide range of depositional environments from shallow reef flat to deep insular shelf carbonate lithofacies representing 10 depositional environments were delineated by comparison with the present day marine sediments and biota around the ryukyus five coral assemblages were defined by species composition and the morphology of fossil forms within the coral limestone each indicating a particular environment the ryukyu group in the study area is composed of 13 lithologic units a complete succession of units commences with coral limestone lst or tst grading upward into rhodolith and larger foraminiferal limestones tst overlain by coral limestone hst episodic subaerial exposure and subordinate karstification commonly occurred after deposition the study area subsided during the deposition of units 1 12 and then was uplifted during deposition of unit 13 reef development may have been dominated by obliquity or precessional cycles sixth and seventh order cycles respectively for the first 0 5 million years 1 5 1 ma after which it may have responded to fifth order eccentricity cycles

mass mortality following disturbance in holocene coral reefs from papua new guinea the frequency and intensity of disturbance on living coral reefs have been accelerating for the past few decades resulting in a changed seascape what is unclear but vital for management is whether this acceleration is natural or coincident only with recent human impact we surveyed nine uplifted early to mid holocene 11 000 3700 calendar cal yr b p fringing and barrier reefs along similar to 27 km at the huon peninsula papua new guinea we found evidence for several episodes of coral mass mortality but frequency was 16 km along the ancient coastline occurred ca 9100 9400 cal yr b p and is associated with a volcanic ash horizon recolonization of the reef surface and resumption of vertical reef accretion was rapid 100 yr but the post disturbance reef communities contrasted with their pre disturbance counterparts assessing the frequency nature and long term ecological consequences of mass mortality events in fossil coral reefs may provide important insights to guide management of modern reefs in this time of environmental degradation and change

pluton emplacement in a strike slip fault zone the doctors flat pluton victoria australia the siluro devonian doctors flat pluton lachlan fold belt australia is a hornblende biotite granite i type that was emplaced into the early silurian omeo metamorphic complex it lies along the ensay fault a major dextral strike slip fault a solid state foliation is developed in much of the pluton with the most intense development at the outer parts grading into massive granite at the centre this foliation is approximately parallel to trace of the ensay fault and to the borders of the pluton it grades into a mylonitic fabric along the ensay fault in the eastern part of the pluton a second fabric is developed giving rise to s c fabrics indicating dextral shear some microfabrics in the pluton are typical of relatively high temperature deformation consistent with syntectonic emplacement but lower temperature microstructures overprint them and are dominant a possible mechanism of intrusion involves the pluton being emplaced into a dilational section of the ensay fault when a jog in the fault opened up into a pull apart structure as intrusion continued the northeastern branch of the pull apart took up all the movement with later intrusive material being less deformed along the ensay fault lower grade assemblages of chlorite epidote albite sphene and cataclastic textures developed at lower temperatures as fault displacement continued during and after cooling of the pluton

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

late holocene reef ecosystem baseline field evidence from the raised reef terraces of kodakara and kikai islands ryukyu islands japan abstract to better understand and evaluate how present day and future reef ecosystems are being impacted by natural climate change and human activity it is important to establish reef ecosystem baselines from paleoecological records here we present paleoecological data including coral cover and genus and species composition for two raised reef islands kodakara and kikai islands located in the ryukyu islands japan covering the last 2 4 and 4 1 kyr respectively evidence of a mean cover of 20 40 coral on pristine reefs at the study sites was found for a millennial scale period of ocean environment stability in terms of sea level solar radiation and sea surface temperature this coral cover has been maintained on the modern reef at kikai island since at least 4 1 kyr ago the coral community was a reef crest upper reef slope community with acropora and goniastrea as the dominant genera and acropora digitifera and goniastrea retiformis as the dominant species from the late holocene to present millennial scale persistence of a digitifera and g retiformis may have been influenced by a strong kuroshio current increased genetic diversity and an increased potential for adaptation to environmental conditions our coral cover and species composition results provide important information for the development of effective reef restoration plans in light of the likely future degradation of reefs

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

coseismic and postseismic creep in the andaman islands associated with the 2004 sumatra andaman earthquake 1 two field campaigns march 2005 and march 2006 for measurements of biological indicators and eyewitness accounts confirm that large coseismic and postseismic surface deformation occurred over the andaman islands in association with the 2004 sumatra andaman earthquake amount of uplift was as large as 1 3 m in the islands off nw coast and decreased to ese with a zone of subsidence in the se andaman the coseismic deformation did not generate large seismic waves or tsunamis indicating that slip was much slower than that off sumatra the coseismic uplift was followed by postseismic subsidence which was evidenced by local residents to have occurred within two months after the earthquake a simple dislocation model explains the deformation pattern by a coseismic rupture 50 km wide with its down dip limit 130 km east of the trench axis followed by an up dip propagation of the rupture front for about 10 km

high precision and high resolution carbonate 230th dating by mc icp ms with sem protocols abstract to facilitate the measurement of u th isotopic compositions suitable for high precision and high resolution 230th dating of coral and speleothem carbonates secondary electron multiplier sem protocol techniques for multicollector inductively coupled plasma mass spectrometry mc icp ms have been developed the instrumental sensitivities are 1 2 with a precision of 1 2 2 for abundance determination of 50 200 fg 234u 1 4 ng 238u or 230th this method features chemistry refinements improvements to procedural and instrumental blanks spectral inference reductions and careful consideration of non linear sem behavior measurement consistency of this mc icp ms combined with previous mass spectrometric results on u th standards and a variety of carbonates demonstrates the validity of the sem protocol method for fossil corals a routine u th isotopic determination at permil level precision requires only 10 50 mg of carbonate as little as 200 mg of young coral with an age of less than 20 yr can be dated with a precision of 0 3 0 8 yr about 20 200 mg speleothem samples with sub ppm to ppm u are required to earn a 5 precision on ages from 5 to 100 kyr requirement of small sample size 10 100s mg carbonate can permit high temporal resolution to date speleothems with slow growth rates i e 1 10 mm kyr this high precision 230th chronology is critical to accurately establish age models date events and splice geochemical proxy time series records from multiple samples in the fields of paleoclimatology and paleoceanography the u th isotopic determination techniques described here can also be applied to different environmental samples such as waters rocks and sediments

event preservation in lagoonal reef systems paleontological data suggest that coral populations in the caribbean were consistently healthy for the past 2 3 k y beginning in the 1980s however disease outbreaks bleaching episodes hurricanes and other perturbations caused catastrophic coral mortality and regional turnover an alternative hypothesis based on historical sources posits that coral populations were already declining more than a century ago these hypotheses can be distinguished only if turnover events are reliably preserved in the holocene record of coral reefs push cores extracted from uncemented lagoonal reefs in belize showed that a direct hit by hurricane iris in 2001 did not disrupt the signature of the recent turnover event which entered the subfossil record essentially intact cores from lagoonal systems in several areas of the caribbean do not support the hypothesis that corals declined before the 1980s

biogeography of holocene coral species in the western indian ocean abstract understanding the relationship between coral biogeography and reef development is a key topic in sedimentology and paleoecology although the knowledge of coral reef growth and internal facies patterns during the holocene has increased since the 1970s the biogeography of holocene coral species in the indo pacific regions remains poorly constrained in this study we examined quantitative records of coral species based on data from five cores retrieved from two holocene reefs in the western indian ocean la pointe au sable reef on mauritius island and toliara reef on madagascar our results indicate that the dominant reef building corals on both reefs were isopora palifera acropora robusta abrotanoides complex some corals e g the a robusta abrotanoides complex and acropora digitifera from 6 ka were found in mauritius whereas these were not identified in the cores from madagascar before 1 5 1 ka this delay may have been controlled by ocean currents and or the competency period of the coral larvae a comparison of these coral assemblages with those in other regions seychelles mayotte ryukyu islands palau islands papua new guinea the great barrier reef new caledonia and vanuatu showed that i palifera was common in all of the studied regions whereas goniastrea retiformis probably migrated recently to mauritius and madagascar in response to prevailing surface ocean currents including the south equatorial current and the agulhas current one explanation for the late arrival of g retiformis to the study sites could be that the competency period of g retiformis larvae is shorter than that of i palifera moreover our quantitative analysis suggests that a given population size during the holocene may have contributed to the abundance of species in modern reefs this study emphasizes the need for further quantitative research on holocene coral species in other regions to better understand the temporal and spatial patterns of coral biogeography

mid holocene coral community data as baselines for understanding contemporary reef ecological states land use changes and associated deteriorations in water quality are cited as major drivers of marine ecosystem change and can modify community abundance and diversity on coral reefs this study uses palaeoecological data derived from a mid holocene age coral reef in the wet tropics region of australia s great barrier reef to develop a record of coral community composition and diversity from a period that significantly pre dates european settlement in the region major changes in catchment sediment and nutrient yields since european settlement have been documented and thus the data presented provides a baseline against which to compare contemporary ecological datasets natural variations in coral assemblage composition as preserved in core records clearly occurred in this mid holocene reef and were associated with the reef shallowing to sea level as it accreted vertically comparisons between modern and mid holocene coral community data from equivalent water depths did not reveal marked shifts in coral community composition and diversity suggesting the long term persistence of a resilient coral assemblage over these time periods

key species of hermatypic coral for reef formation in the northwest pacific during holocene sea level change abstract cores from holocene reefs provided a growth history and species level identification of corals and demonstrated the most important reef builders during the formation stage this knowledge is important to determine a principle for reef formation and to provide preservation plans in the near future a biological and sedimentological study of sediment cores recovered from the palau islands and yoron island northwest pacific revealed four major facies corymbose acropora arborescent acropora massive porites and detritus species level observations show that arborescent acropora a muricata and a intermedia contributed to reef growth under low to moderate energy conditions whereas corymbose and tabular acropora a digitifera a hyacinthus and a robusta a abrotanoides and i palifera were key species for reef formation under high energy conditions during holocene sea level rise and the ensuing period of sea level stability once sea level had stabilized massive porites became restricted to areas subjected to low energy turbid conditions these key species are successful corals because the ecological strategy is rapid growth determinate growth a high degree of colony integration strongly resistant to wave action and rapid local dispersion via fragmentation moreover the western boundary current kuroshio flows along the reefs in the northwest pacific and it is easy for key species to distribute throughout the region during the period of holocene sea level rise and stabilization these features are a principle for reef formation during sea level changes these key species played a significant role in holocene reef formation in the northwest pacific however coral mortality caused by climate change has recently been widely reported moreover the decrease in key species abundance in present day reefs has been more severe than that in any other species these geological findings have important implications regarding the appropriate use of coral transplantation and decisions regarding the optimal location and size of marine protected areas

holocene sea level record from corals reliability of paleodepth indicators at ishigaki island ryukyu islands japan abstract holocene sea level change provides direct evidence of the melting of ice sheets however our understanding of the timing and course of such change is limited by a lack of information regarding environmental condition of corals for example holocene sea level curves are compiled based on water depths estimated from the occurrence of a small number of coral species as species identification is difficult work the error associated with this method of estimating sea level exceeds 2 5 m in addition there generally occurs a difference in the living water depth of corals between high energy reefs and low to moderate energy reefs this difference in living water depth also results in an error in reconstructed sea level curves in the present study we analyzed drill core and recorded the vertical distribution of corals at the high energy ibaruma reef and low to moderate energy fukido reef ishigaki island ryukyu islands japan analyses of corymbose acropora a digitifera massive goniastrea g retiformis massive pocillopora p verrucosa massive platygyra p ryukyuensis and other corals enables the accurate reconstruction of a sea level curve because these species are distributed in a narrow range with a weighted mean m w error of between 0 5 and 2 5 m these observation data from ibaruma and fukido reefs can be used to reconstruct holocene sea level curves based on drill core data from ibaruma reef however the two reefs yield contrasting sea level curves the curve reconstructed based on data from fukido reef is several meters deeper than that reconstructed based on data from ibaruma reef this discrepancy reflects the different energy levels of the two reefs high energy at ibaruma reef and low to moderate energy at fukido reef therefore the accurate reconstruction of a holocene sea level curve requires the identification of species from drill core and observations of the vertical distribution of species at the present day reef at a location close to the drilling site the holocene sea level curve reconstructed based on drill core data from ibaruma reef reveals a rapid sea level rise of approximately 7 5 m kyr 1 between 8000 and 6000 cal years bp the rate of sea level rise decreased from 7 5 to 3 5 m kyr 1 between 6000 and 5000 cal years bp a mid holocene highstand occurred at around 5000 cal years bp at a level of approximately 3 2 5 m above the present mean sea level the increase in ocean volume corresponding to this sea level rise indicates that melting of the antarctic ice sheet continued beyond 6000 cal years bp as most of the northern hemisphere ice sheets had melted by 6000 cal years bp resulting in sea levels similar to those of the present day

non darcian flow in fractured rocks with a linear flow pattern abstract groundwater flow through fractured rocks deserves special study due to its deviation from the classical darcian solutions the occurrence of linear flow towards extensive or medium length dipping geological structures such as faults joints contact surfaces and fractures is rather common especially in igneous and metamorphic rock environments in general these structural elements have permeabilities of many orders of magnitude greater than the host rock drilling any well in these structures is preferable since the hydraulically connected combination of the well and these main structures provides a surface which has an area several times greater than the well surface as a result of such combinations flow lines become parallel well losses are reduced and abstraction of water becomes easier most of the host rock of the main structures has fractures and fissures secondary flow in these conduits violates the darcian law because the type of flow becomes turbulent especially at high velocities hence it is the main purpose of this paper to present an analytical solution to account for the turbulent flow by means of the forchheimer law the results are documented in the form of type curves which give opportunity for practicing hydrogeologists to determine the aquifer parameters by a type curve matching procedure various graphs are presented to compare darcian and non darcian flows in fractured media application of the methodology developed herein is shown for some realistic field data

holocene variability of the kuroshio current in the okinawa trough northwestern pacific ocean abstract cores 255 and b 3gc from the southern and northern okinawa trough respectively were studied for determining the variability of the kuroshio current on centennial scales during the holocene based on detailed ams 14 c dates stable isotope and planktonic foraminiferal distribution the main flow of the kuroshio current was inferred to re enter the okinawa trough at 7 3 calendar cal kyr bp leading to abrupt changes in sedimentation rate remarkably increased abundance of the kuroshio current indicator pulleniatina obliquiloculata increased sea surface temperature sst and depth of thermocline dot during 4 6 2 7 cal kyr bp the abundance of p obliquiloculata sharply decreased corresponding to a decreases in sst and dot implying that the influence of the kuroshio current weakened at that time possibly as a result of the intensified winter monsoon significantly the kuroshio current proxies e g the difference in sst between the southern and northern okinawa trough display periodicities of 1500 yr and 700 800 yr ascribed to the second harmonic of the 1500 yr cycle in oceanic thermohaline circulation during the holocene the holocene events at 0 6 1 7 3 3 4 6 5 9 8 1 9 4 cal kyr bp in the okinawa trough appear to be the most recent manifestation of the millennial scale climate cycle recorded in the north atlantic arabian sea marine sediment cores and greenland ice cores suggesting global climatic tele connections

1200 year paleoecological record of coral community development from the terrigenous inner shelf of the great barrier reef increased terrestrial sediment and nutrient yields are regarded as significant threats to coral reef health within the central great barrier reef lagoon where water quality has reportedly declined since european settlement since ca a d 1850 inner shelf reef conditions have purportedly deteriorated however the link between reef decline and water quality change remains controversial primarily because of a lack of pre european period ecological baseline data against which to assess contemporary ecological states here we present a high resolution record of reef accretion and coral community composition from a turbid zone nearshore reef on the inner shelf of the great barrier reef the record is based on six radiocarbon date constrained cores and extends back to ca 1200 calibrated yr b p results demonstrate not only the potential for coral communities to initiate and persist in settings dominated by fine grained terrigenous sediment accumulation but also that a temporally persistent but low diversity suite of corals has dominated the reef building community at this site for at least the past millennium furthermore the coral assemblages exhibit no evidence of community shifts attributable to post european water quality changes while extrapolation of these findings to other turbid zone reefs must remain tentative the study raises important questions about the resilience of inner shelf reefs that are under terrestrial sediment influence and subject to elevated turbidity conditions and demonstrates the potential to develop detailed millennial time scale coral community records from holocene reef systems

holocene sea level change and tectonic uplift deduced from raised reef terraces kikai jima ryukyu islands japan abstract kikai jima kikai island is surrounded by four holocene raised coral reef terraces which are thought to be an offlapping sequence of reef deposits caused by combined effects of seismic uplift and holocene sea level change many studies in this region have investigated holocene sea level changes and reef growth but there are relatively few in which reliable sea level indicators are given we have found that pocillopora verrucosa one of the most abundant coral species on the upper reef slopes of fringing reefs in the ryukyus has its peak abundance at a depth of 1 5 m therefore this species is considered ideal for the analysis of relative sea level change and can be used as a dipstick for the holocene reef deposits in this area based on the distribution of p verrucosa on the four holocene raised terraces we calculate relative paleo mean sea levels to be 10 8 11 1 and 8 5 8 9 m for terrace i 5 0 5 3 m for terrace ii 4 0 4 3 m for terrace iii and 1 9 2 5 m for terrace iv these results combined with hitherto known and newly measured radiometric dates 103 total clearly show that the four terraces formed in response to repeated seismic uplifts at 6 3 4 1 3 1 and 1 4 ka and that sea level was higher than present between 7 0 and 6 3 ka

variation of initial 230th 232th and limits of high precision u th dating of shallow water corals one hundred eighty u th data including 23 isochrons on 24 pristine modern and holocene corals and 33 seawater samples were analyzed using sector field mass spectrometry to understand the variability of initial 230th 232th 230th 232th0 this dataset allows us to further assess the accuracy and precision of coral 230th dating method by applying quality control including careful sampling and subsampling protocols and the use of contamination free storage and workbench spaces the resulting low procedural blanks give an equivalent uncertainty in age of only 0 2 0 3 yr for 1 2 g of coral sample using site specific 230th 232th0 values or isochron techniques our study demonstrates that corals with an age less than 100 yrs can be 230th dated with precisions of 1 yr six living subtidal coral samples were collected from two continental shelf sites nanwan off southern taiwan in the western pacific and son tra off central vietnam in the south china sea one coral core was drilled from an open ocean site santo island vanuatu in the western tropical pacific and modern and fossil intertidal coral slabs 17 in total were cut from six sites around the islands of simeulue lago north pagai and south pagai of sumatra in the eastern indian ocean the results indicate that the main source of thorium is the dissolved phase of seawater with variation of 230th 232th0 depending on local hydrology with intense input of terrestrial material low 230th 232th0 atomic ratios of 4 9 10 6 and 3 2 10 6 with a 10 variation are observed in nanwan and son tra respectively at the santo site we find a value of 5 6 10 6 at 4 horizons and one high value of 24 10 6 in a sample from ad 1974 6 0 5 likely due to the upwelling of cold water during a la nina event between ad 1973 and 1976 the natural dynamics of 230th 232th0 recorded in the intertidal corals at sites in the sumatran islands are complicated so that this value varies significantly from 3 0 to 9 4 10 6 three of the 141 modern coral 230th ages differ from their true ages by 23 to 4 indicating the presence of detrital material with anomalous 230th 232th values duplicate measurement of coeval subsamples is therefore recommended to verify the age accuracy this improved high precision coral 230th dating method raises the prospects of refining the age models for band counted and tracer tuned chronologies and of advancing coral paleoclimate research

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

late holocene eustatic sea level changes deduced from geomorphological features and their 14c dates in the ryukyu islands japan abstract this paper deduces late holocene eustatic sea level changes from 14 c dates and present elevations of almost all holocene raised coral reefs in the ryukyu islands an active island arc without the assumption of a constant uplift rate stable relative sea levels are restored by using sea level indicators such as raised coral reef terraces fossil coral wave cut notches and beach rock the oldest and the youngest 14 c ages of calcium carbonate fossils collected from a depositional terrace surface show their formative period when all relative sea level changes of thirteen islands are compared the ryukyu islands form three groups according to the oldest age in the formative period of the holocene raised reef terraces in each island that is 6500 yr b p 5000 yr b p and 3500 yr b p the youngest of the terrace formative periods in the three island groups correspond with each other one eustasy explains the seismic upheaval and the formative process of the terrace surfaces of the three island groups the eustatic sea level trend in the ryukyu islands can be summarized as follows from 6500 to 3500 yr b p the sea level continued to rise generally around 6500 yr b p 5000 to 3500 yr b p and 3500 to 1700 yr b p the rates of sea level rise became slower the sea level between 3500 and 1700 yr b p was stable and it has been the highest in the holocene at that time its height was less than 1 0 m above the present sea level the holocene uplift rate of each island is estimated to be half to three times as great as that of the last 125 000 years the uplift rates of the three island groups in the late holocene are inferred to have been decreasing exponentially the crustal movement and the distribution of raised coral reefs are further discussed here