holocene turn on and evolution of the southern great barrier reef revisiting reef cores from the capricorn bunker group abstract extensive drilling of the great barrier reef gbr in the 70s and 80s illuminated the main factors controlling reef growth during the holocene however questions remain about 1 the precise nature and timing of reef turn on or initiation 2 whether consistent spatio temporal patterns occur in the bio sedimentologic response of the reef to holocene sea level rise then stability and 3 how these factors are expressed in the context of the different evolutionary states juvenile mature senile reefs combining 21 new c 14 ams and 146 existing re calibrated radiocarbon and u th ages we investigated the detailed spatial and temporal variations in sedimentary facies and coralgal assemblages in fifteen cores across four reefs wreck fairfax one tree and fitzroy from the southern gbr our newly defined facies and assemblages record distinct chronostratigraphic patterns in the cores displaying both lateral zonation across the different reefs and shallowing upwards sequences characterised by a transition from deep porites faviids to shallow acropora isopora coral types the revised reef accretion curves show a significant lag period ranging from 0 7 2 ka between flooding of the antecedent pleistocene substrate and holocene reef turn on this lag period and dominance of more environmentally tolerant early colonizers e g domal porites and faviids suggests initial conditions that were unfavourable for coral growth we contend that higher input of fine siliciclastic material from regional terrigenous sources exposure to hydrodynamic forces and colonisation in deeper waters are the main factors influencing initially reduced growth and development all four reefs record a time lag and we argue that the size and shape of the antecedent platform is most important in determining the duration between flooding and recolonisation of the holocene reef finally our study of capricorn bunker group holocene reefs suggests that the size and shape of the antecedent substrate has a greater impact on reef evolution and final evolutionary state mature vs senile than substrate depth alone

chronostratigraphy of bramston reef reveals a long term record of fringing reef growth under muddy conditions in the central great barrier reef inshore reefs on australia s great barrier reef gbr are widely argued to be in decline although recent reports suggest that some may be more resilient than traditionally assumed resolution of this debate requires long term insights into past reef development and variability to provide context for the assessment of present reef condition long term reef growth histories can preserve extended records of reef growth and condition however they are rare especially for mainland attached fringing reefs which are themselves uncommon on the gbr we examined the internal structure and ecology at bramston reef a mainland attached fringing reef located in a protected bay on the central gbr eight reef matrix cores were collected across the reef flat sedimentological and palaeo ecological analyses coupled with u th dating were used to develop the first reef growth history for a shore attached fringing reef in this region twenty five hard coral genera were identified in the palaeo ecological analyses the key reef building genera including acropora montipora euphyllia porites and goniopora have contributed to reef growth since initiation and are represented in the extant coral community despite a change in accretion mode during the late holocene sedimentological and stratigraphic investigations demonstrate bramston reef has always grown in a mud rich setting u th ages indicate that reef initiation occurred at or before 5400 ybp in a palaeo water depth of 2 3 m bramston reef reached sea level by 4256 ybp when sea level was approximately 1 m higher than present after which rapid seaward progradation occurred until around 3000 ybp 19 cm yr on average between approximately 3000 and 1000 ybp seaward progradation of the reef flat slowed to 9 8 cm yr on average this deceleration of reef growth occurred long before european settlement of the queensland coast and was driven by natural constraints probably associated with limited accommodation space due to late holocene sea level fall our results demonstrate that mainland attached reef initiation and accretion can occur in muddy inshore environments over long timeframes centuries to millennia

high frequency of super cyclones along the great barrier reef over the past 5 000 years understanding long term variability in the occurrence of tropical cyclones that are of extreme intensity is important for determining their role in ecological disturbances1 2 3 4 5 for predicting present and future community vulnerability and economic loss6 and for assessing whether changes in the variability of such cyclones are induced by climate change7 our ability to accurately make these assessments has been limited by the short less than 100 years instrumented record of cyclone intensity here we determine the intensity of prehistoric tropical cyclones over the past 5 000 years from ridges of detrital coral and shell deposited above highest tide and terraces that have been eroded into coarse grained alluvial fan deposits these features occur along 1 500 km of the great barrier reef and also the gulf of carpentaria australia we infer that the deposits were formed by storms with recurrence intervals of two to three centuries8 9 10 11 and we show that the cyclones responsible must have been of extreme intensity central pressures less than 920 hpa our estimate of the frequency of such super cyclones is an order of magnitude higher than that previously estimated which was once every several millennia12 13 14 and is sufficiently high to suggest that the character of rainforests and coral reef communities were probably shaped by these events

sediment flux across the great barrier reef shelf to the queensland trough over the last 300 ky the continental margin off northeast australia comprising the great barrier reef gbr platform and queensland trough is the largest tropical mixed siliciclastic carbonate depositional system in existence we describe a suite of 35 piston cores and two ocean drilling program odp sites from a 130 240 km rectangular area of the queensland trough the slope and basin setting east of the central gbr platform oxygen isotope records physical property magnetic susceptibility and greyscale logs analyses of bulk carbonate content and radiocarbon ages at these locations are used to construct a high resolution stratigraphy this information is used to quantify mass accumulation rates mars for siliciclastic and carbonate sediments accumulating in the queensland trough over the last 31 000 years for the slope highest mars of siliciclastic sediment occur during transgression 1 0 million tonnes per year mt yr 21 and lowest mars of siliciclastic 0 1 mt yr 21 and carbonate 0 2 mt yr 21 sediment occur during sea level lowstand carbonate mars are similar to siliciclastic mars for transgression and highstand 1 1 1 4 mt yr 21 in contrast for the basin mars of siliciclastic 0 0 1 mt yr 21 and carbonate sediment 0 2 0 4 mt yr 21 are continuously low and within a factor of two for lowstand transgression and highstand generic models for carbonate margins predict that maximum and minimum carbonate mars on the slope will occur during highstand and lowstand respectively conversely most models for siliciclastic margins suggest maximum and minimum siliciclastic mars will occur during lowstand and transgression respectively although carbonate mars in the queensland trough are similar to those predicted for carbonate depositional systems siliciclastic mars are the opposite given uniform siliciclastic mars in the basin through time we conclude that terrigenous material is stored on the shelf during sea level lowstand and released to the slope during transgression as wave driven currents transport shelf sediment offshore q 2000 elsevier science b v all rights reserved

regional change of coda q in the oceanic lithosphere coda q of 22 local earthquakes recorded on islands located in young and old oceanic lithosphere areas has been measured we found that the q values at periods of from 1 to 2 seconds increase from young to old ocean lithosphere in the same way as for the continent where the intensity of current tectonic activity shows a strong negative correlation with the coda q the q values increase with frequency proportional to fn where n was found to be 0 46 0 61 with the higher values for younger oceanic lithosphere which is again similar to the continents where the active regions have higher n values

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

holocene development of the belize barrier reef previously knowledge of the holocene development of the belize barrier reef bbr the largest reef system in the atlantic ocean was limited to one location carrie bow cay we present new data from 11 rotary drill cores taken at 9 locations and 36 radiometric ages that indicate that the bbr was established from 8 26 to 6 68 ky bp on pleistocene reef limestones presumably deposited during oxygen isotope stage 5 the nonsynchronous start of holocene reef growth was a consequence of variation in elevation of antecedent topography largely controlled by underlying nne trending structures from north to south pleistocene elevation decreases along these structural trends probably reflecting differential subsidence and variations in karst topography reef anatomy is characterized by three facies in order of decreasing abundance these facies are represented by corals mainly acropora palmata and members of the montastraea annularis group by unconsolidated sand and rubble and by well cemented coral grainstones rudstones holocene reef accumulation rates average 3 25 m ky the degree of reef consolidation is negatively correlated with holocene thicknesses indicating that slowly growing reefs are better cemented than fast growing ones we present a holocene sea level curve for belize based on 36 dates from this study and 33 dates from our previous studies in the area

evidence for smoothly falling sea level relative to north queensland australia during the past 6 000 yr post glacial sea level curves are expected to differ between different parts of the world as a result of global isostatic changes1 or perhaps other forms of geoidal changes2 i report here results from the inner part of the northern great barrier reef which seem to show a pattern of smoothly falling sea level during the past 6 000 yr the results are consistent with stratigraphical results from prograded mangrove coasts on the nearby north queensland mainland the region is remote from the tectonically active margin of the south west pacific ocean and the results contribute to the global data set relevant to isostatic changes being assembled by the international sea level project igcp project no 61 they also provide a baseline relevant to holocene coral reef growth in the inner great barrier reef

late pleistocene and holocene sea level change along the australian coast abstract tectonically the australian continent is relatively stable and as such it provides a good platform for studying late pleistocene and holocene sea level change the observations indicate that present sea level was reached at about 6000 years ago and that since then level has remained constant to within a few metres considerable spatial variability in the amplitude of the emergence and in the time at which sea levels first reached their present values have been observed spatial variability has also been observed in the sea level during the last glacial maximum and during the late phase of the holocene transgression much of this variaiblity is the result of the earth s adjustment to the glacial melting in the late pleistocene early holocene time and the concomitant distribution of this meltwater into the oceans conclusions that are drawn from matching observations with this glacio hydro isostatic model include the following 1 the mantle viscosity increases with depth the average upper mantle viscosity is about 2 3 10 20 pa s and the average lower mantle defined as below 670 km depth viscosity is about 10 22 pa s the average lithospheric thickness for the coastal and offshore region is about 70 80 km lateral variations in these mantle parameters are indicated 2 the addition of melwater into the oceans did not cease 6000 years ago but continued at a reduced rate up to more recent times adding an amount of water equivalent to a 3 m sea level rise in this interval 3 the amplitude of the holocene emergence is a function inter alia of coastal geometry and significant variations occur over distances of a few hundred kilometres and more holocene highstands of 1 2 m are generally well developed at the continental margins but are less well developed or do not developed at all at offshore islands and reefs 4 variations in the time of maximum emergence also occur being earlier at upstream tidal river sites than at coastal sites at offshore reefs or islands the sea level curve lags the coastal curves by 1000 years or more 5 considerable spatial variability occurs in the sea levels at the time of the last glacial maximum with variations of up to 30 m occurring across the continental shelves 6 there is generally no need to invoke tectonic movements to explain the sea level data along the australian coast but possible exceptions occur for the perth region and for tasmania

successive phases of holocene reef flat development evidence from the mid to outer great barrier reef a re examination of 46 recently published u th reef flat ages from heron and one tree reefs in the southern great barrier reef gbr identified several distinct holocene reef growth phases with a clear 2 3 kyr hiatus in lateral reef accretion from 3 9 ka to 1 5 ka an analysis of all available published radiocarbon reef flat ages 165 from 27 other mid outer platform reefs revealed a similar hiatus between 3 6 ka and 1 6 ka for the northern south central and southern gbr however no hiatus in reef flat growth was observed in reefs from the central gbr with ages ranging from 7 6 ka to 0 9 ka increased upwelling turbidity and cyclone activity in response to increased sea surface temperature sst s precipitation and el nino southern oscillation variability have been ruled out as possible mechanisms of reef turn off for the mid outer platform reefs rather a fall 0 5 m in relative sea level at 4 3 5 ka is the most likely explanation for why reefs in the northern and southern regions turned off during this time greater hydro isostatic adjustment of the central gbr and long term subsidence of the halifax basin may have provided greater vertical accommodation for the mid outer reefs of the central gbr thus allowing these reefs to continue to accrete vertically despite a fall in sea level 4 3 5 ka further evidence for greater subsidence in this region includes the lack of senile reefs and dominance of incipient and juvenile reefs in the central gbr this suggests that these reefs approached sea level considerably later than the northern and southern reefs consistent with their deeper antecedent substrates thus these results not only provide important information about possible reef flat demise in response to natural environmental factors but also provide insights into regional subsidence that affected relative sea level along the east australian margin during the holocene

tidal jets nutrient upwelling and their influence on the productivity of the alga halimeda in the ribbon reefs great barrier reef abstract a field experiment was carried out to study water circulation and benthic biological productivity near a passage through the ribbon reefs in the northern great barrier reef of australia the currents through the passage were phase locked with the tide during rising tides strong currents through the passage generated localized upwelling on the upper continental slope enriching the depleted surface waters in nutrients particularly nitrate and phosphate simultaneously on the shelf side of the passage a tidal jet vortex pair system developed which separated from the ribbon reefs so that the coral reefs themselves received little of the upwelled water this was propagated as a bottom trapped layer towards the meadows of the calcareous alga halimeda situated several kilometres inshore of the reefs halimeda can accumulate nutrients particularly nitrate from the relatively low concentrations available from the upwelling events the quantity of nitrogen upwelled was more than sufficient to supply the total nitrogen requirements of the halimeda vegetation a tidal jet also formed offshore from the reef passage during falling tides and the coral covered offshore side of the ribbon reefs may be sustained by the subsequent vertical turbulent entrainment into the jet of deep nutrient rich water immediately offshore from the reef passages these processes require a continuous barrier reef with only narrow passages several kilometers apart numerical models successfully reproduce the observations of jet driven upwelling and of the dynamics of the tidal jet vortex pair system the model predictions are very sensitive to the details of the bathymetry of reef passages as such data are presently unavailable it is not yet possible to use these models to calculate the jet driven nutrient upwelling for the whole great barrier reef

recurrent patterns of coral community and sediment facies development through successive phases of holocene inner shelf reef growth and decline abstract coral community decline and resultant turn off of reef accretion potential are commonly predicted outcomes of the increasing environmental stresses experienced by many coral reefs the potential for coral reef communities to re establish once environmental conditions ameliorate or new substrates for colonisation become available are however less well understood here we discuss data from a fringing reef at dunk island an inner shelf high island on australia s great barrier reef gbr although this reef is spatially contiguous detailed coring and dating reveal it was constructed in two discrete temporal phases the inner part of the reef flat formed first during the late stages of the post glacial marine transgression early sea level highstand 6 9 4 5 k cal yr b p whereas the outer fringe developed after the late holocene sea level regression from 1 6 k cal yr b p to present a hiatus of almost 3000 years separates the two reef growth phases data from this reef thus provide a same site perspective on the degree of temporal continuity that exists where an actively growing reef slows and eventually ceases to accrete for an extended period before re establishing and growing again a temporal transition equivalent to reef turn off followed by renewed reef turn on the depositional architectures of the two phases of reef growth are very similar as are patterns of facies and coral assemblage development this study suggests that reefs over the timescales at which cycles of reef turn on and turn off operate the centennial to millennial timescale can not only re establish successfully but also that regrowth may be characterised by the establishment of near identical reef building communities and the development of near identical depositional structures these findings thus have direct relevance to the on going debate about whether and in what form reef communities will be able to re establish themselves following periods of suppressed growth such as those projected for the near future

rapid relative sea level fall along north eastern australia between 1200 and 800 cal yr bp an appraisal of the oyster evidence a fast paced post glacial sea level rise and subsequent mid holocene sea level highstand are well documented at several far field locations away from the presence of former ice sheets but sea level development during the late holocene remains ambiguous in this study we present new data from modern and fossil oysters attached to shoreline rocks along the north eastern australian coastline that reveal new constraints on the nature and timing of relative sea level change over the past 2500 yr surveyed elevations of various contemporary oyster zones contextualize modern oyster growth forms in relation to sea level datum and build the reference for our fossil oyster data based on survey data and field observations we developed a robust set of criteria for measuring fossil oysters to determine their relative sea level position and constrain the uncertainties associated with these reconstructions thick 10 cm fossil oyster visors above the equivalent modern growth suggest higher relative sea levels in the past i e 1200 cal yr bp radiocarbon analyses of the modern oyster visors suggest continuous lateral accumulation over the past 800 yr which implies relatively stable sea level over this period the modern and fossil dataset defines a distinct and rapid relative 1 m sea level fall between 1200 and 800 cal yr bp whether the sea level fall was stepped or followed a broader smooth monotonic pattern is unclear the timing coincides with the initiation of some inshore fringing coral reefs in the great barrier reef region and other major geomorphological changes along the coastal zone a combination of various factors may have been the driving mechanism behind this relative sea level fall with rates between 1 0 to 5 2 mm yr 1

late quaternary siliciclastic carbonate sedimentation model for the capricorn channel southern great barrier reef province australia abstract a model is presented for hemipelagic siliciclastic and carbonate sedimentation during the last glacial interglacial cycle in the capricorn channel southern great barrier reef gbr stable isotope ratios grainsize carbonate content and mineralogy were analysed for seven cores in a depth transect from 166 to 2892 m below sea level mbsl results show variations in the flux of terrigenous neritic and pelagic sediments to the continental slope over the last sea level cycle during the glacial lowstand terrigenous sediment influenced all the cores down to 2000 mbsl the percentages of quartz and feldspar in the cores decreased with water depth while the percentage of clay increased x ray diffraction analysis of the glacial lowstand clay mineralogy suggests that the siliciclastic sediment was primarily sourced from the fitzroy river which debouched directly into the northwest sector of the capricorn channel at this time the cores also show a decrease in pelagic calcite and an increase in aragonite and high magnesium calcite hmc during the glacial the influx of hmc and aragonite is most likely from reworking of coral reefs exposed on the continental shelf during the glacial and also from hmc ooids precipitated at the head of the capricorn channel at this time mass accumulation rates mars are high 13 5 g cm 3 kyr 1 during the glacial and peak at 20 g cm 3 kyr 1 in the early transgression 16 14 ka bp mars then decline with further sea level rise as the fitzroy river mouth retreats from the edge of the continental shelf after 13 5 ka bp mars remain low 4 cm 3 kyr 1 throughout the holocene highstand data for the holocene highstand indicate there is a reduction in siliciclastic influx to the capricorn channel with little quartz and feldspar below 350 mbsl however fine grained fluvial sediments presumably from the fitzroy river were still accumulating on the mid slope down to 2000 mbsl the proportion of pelagic calcite in the core tops increases with water depth while hmc decreases and is present only in trace amounts in cores below 1500 mbsl the difference in the percentage of hmc in the deeper cores between the glacial and holocene may reflect differences in supply or deepening of the hmc lysocline during the glacial sediment accumulation rates also vary between cores in the capricorn channel and do not show the expected exponential decrease with depth this may be due to intermediate or deep water currents reworking the sediments it is also possible that present bathymetry data are too sparse to detect the potential role that submarine channels may play in the distribution and accumulation of sediments comparison of the capricorn channel mars with those for other mixed carbonate siliciclastic provinces from the northeast margin of australia indicates that peak mars in the early transgression in the capricorn channel precede those from the central gbr and south of fraser island the difference in the timing of the carbonate and siliciclastic mar peaks along the northeast margin is primarily related to differences in the physiography and climate of the provinces the only common trend in the mars from the northeast margin of australia is the near synchronicity of the carbonate and siliciclastic mar peaks in individual sediment cores which supports a coeval sedimentation model

western pacific coral δ18o records of anomalous holocene variability in the el nino southern oscillation 1 skeletal oxygen isotope ratios in holocene porites corals from northern papua new guinea record decreases in sea surface temperature sst and rainfall during el nino events threshold analysis of seven fossil coral 18o records spanning the period 7 6 5 4 ka thousand years ago shows 8 12 el nino events century significantly less than the 23 events century recorded by the nino3 4 index the coral reconstructions also show a 15 reduction in el nino event amplitude for 7 6 5 4 ka compared to today which is greater than the suppression given by model studies in contrast large and protracted el nino events are identified for 2 5 1 7 ka taken together the results indicate a non linear atmospheric response to holocene changes in el nino sst anomalies we propose that small changes in tropical sst gradients the positioning of the intertropical convergence zone and the pacific tradewind climatology modify the impact of el nino events on western pacific rainfall

evidence for the episodic turn on and turn off of turbid zone coral reefs during the late holocene sea level highstand terrigenous sediment accumulation within nearshore marine environments is regarded as a major factor inhibiting carbonate production and coral reef accretion while recent ecological and geological research into reef development under long term terrigenous sediment influence questions the overly simplistic nature of such views understanding of the time scales of reef initiation and growth and the morphodynamics of reef accretion in these settings remains limited here we present evidence to support recent suggestions that once established rapid reef accretion and progradation is possible but that the restricted accommodation windows in which such reefs develop often result in short lived ephemeral phases of reef building specifically we describe two discrete periods of reef growth within one small 600 m wide coastal embayment around a high island on the terrigenous sediment dominated inner shelf of the central great barrier reef australia these reef building phases occurred at either end of the holocene sea level highstand the first during the late postglacial marine transgression and early highstand 6900 4500 calibrated cal yr b p the second following the late holocene regression and stillstand 1600 cal yr b p to present an 3000 yr hiatus occurred between these events probably as a function of subtle changes in sea level and associated shoreline morphodynamics

on the dynamics of interdecadal thermocline depth and sea surface temperature variability in the low to mid latitude pacific ocean the role of upper ocean dynamics in generating interdecadal sea surface temperature sst variations is investigated with the help of the australian bureau of meteorology research centre coupled general circulation model cgcm and a first baroclinic mode shallow water ocean model swm an empirical orthogonal function analysis is performed on the lowpass filtered sst and vertically averaged temperature in the upper 300 m anomaly data output from a 100 year cgcm simulation the dominant mode sst spatial pattern and time variability is consistent with the interdecadal pacific oscillation the swm is forced by wind stresses from the cgcm 100 year simulation to investigate the role of oceanic rossby and kelvin wave propagation on thermocline depth variations the swm produces variability similar to the cgcm interdecadal variability we conclude that large scale wind forced upper ocean dynamics play a dominant role in generating interdecadal upper ocean temperature variations on decadal and longer timescales

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

paleoceanographic evolution of the gulf of tehuantepec mexican pacific during the last 6 millennia oceanographic dynamics in the gulf of tehuantepec gt are the direct consequence of climate variability mainly influenced by the strong wind regime locally called tehuanos and the interactions

variability of surface ocean radiocarbon and stable isotopes in the southwestern pacific we present high precision radiocarbon 14c results and stable isotope 18o and 13c records for a coral from heron island 23 s 152 e and new stable isotope 18o and 13c records for annual coral bands from abraham reef 22 s 153 e in the southern great barrier reef studied earlier druffel and griffin 1993 these tracers provide unique information on the regional water mass history and together these data allow us to constrain the variability of circulation in the upper pacific over the past four centuries first we observe decreases in 18o of coral from abraham reef and heron island indicating an increase in sea surface temperature and or a decrease in surface salinity since 1850 second the small suess effect value 14c decrease from 1880 to 1955 due mostly to fossil fuel co2 observed previously at abraham reef druffel and griffin 1993 is confirmed in the measurements reported here from the heron island coral this value is low compared to those observed in other areas of the ocean druffel 1997 druffel and linick 1978 nozaki et al 1978 between 1880 and 1955 third we report alterations in the correlation between el nino events and the occurrence of low 14c which is indicative of long term change s in circulation in the sw pacific the 14c shifts reported here are not large but even small temporal changes in prebomb 14c suggest that important changes in the large scale state of the ocean have occurred such as a temporal change in circulation

evidence for holocene changes in australian indonesian monsoon rainfall from stalagmite trace element and stable isotope ratios abstract trace element and stable isotope ratios from an active stalagmite lr06 b1 recovered from liang luar cave on the island of flores eastern indonesia are used to reconstruct the position of the austral summer inter tropical convergence zone and australian indonesian summer monsoon variability during the holocene uranium series dating of the stalagmite shows that it commenced growth 12 640 years ago with hiatuses spanning 8 560 to 6 420 and 3 670 to 2 780 years ago stalagmite mg ca and sr ca ratios correlate significantly with one another and with 18 o and 13 c throughout the record this suggests that the mg ca and sr ca ratios are dominated by prior calcite precipitation a process whereby degassing in the vadose zone during periods of low recharge causes deposition of calcite and disproportionate loss of ca 2 ions relative to mg 2 and sr 2 upstream of the stalagmite the degree of initial 234 u 238 u disequilibrium also appears to have been controlled by recharge to the overlying aquifer together with the mg ca sr ca and 18 o values the initial uranium isotope activity ratios 234 u 238 u i imply a generally drier early holocene coincident with a lower sea level and lower southern hemisphere summer insolation comparison of speleothem 18 o time series from flores and borneo shows that they vary in unison for much of the holocene however there is a significant decrease in the borneo 18 o record 6 000 to 4 000 years ago that does not occur in the flores record this anomaly may be related to a change in the australian indonesian summer monsoon circulation in response to a protracted positive phase of the indian ocean dipole under this scenario stronger upwelling off of western indonesia would based on present day effects result in reduced summer convective activity over flores and a subsequent northward shift of the intertropical convergence zone

cyclone frequency during the last 5000 years at curacoa island north queensland australia abstract a series of storm deposits at curacoa island a steep bedrock island in the palm group north queensland record the passage of cyclonic events storm ridge accretion occurs when cyclonic waves and surge combine to transport coarse sediment mostly broken coral onto the shore and deposit it above normal tidal levels narrow fringing reefs at curacoa act as a rapidly replenished sediment source augmented by lithic gravel transported longshore beachface stormberm ridge platform and washover deposits can accrete during a single event a series of storm ridges were examined via stratigraphic pits and trenches on two traverses deposits from 22 events were identified and their ages were determined using 68 radiocarbon dates from coral clasts most dates from each storm deposit formed statistically accordant groups only 15 of the dates were older than the group ages and were interpreted as reworked specimens accordant ages within each group were combined and converted to calibrated radiocarbon ages ridge ages decrease uniformly with distance from the oldest ridge indicating uniform depositional processes over the last 5000 years a time series of storm deposit ages indicates that cyclone frequency was statistically constant over the last 5000 years this suggests that cyclone frequency may not have been affected by sea surface temperatures in the region which appear to have been about 1 c warmer about 5000 years ago gagan m k ayliffe l hopley d cali j mortimer g chappell j mcculloch m head m j 1998 temperature and surface water balance of the mid holocene tropical western pacific science 279 1014 1018

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

late pleistocene and holocene sea level change in the australian region and mantle rheology summary spatial and temporal variations in sea level are produced by the melting of the late pleistocene ice and by the earth s response to the redistribution in surface loads by examining different parts of the sea level curves of the past 20 000 yr from geographically widely distributed regions it becomes possible to constrain models of the melting history of the ice sheets and of the earth s rheology observations from sites away from the former arctic ice sheets such as the australian and south pacific region are particularly important for constraining the total meltwater volumes added into the oceans in the past 20 000 yr and the rates at which this occurred these observations indicate that the antarctic ice sheets provided a significant contribution to the sea level rise at a rate that was approximately synchronous with the melting of the laurentide ice sheet except for the interval 9000 6000 yr ago when it may have lagged behind minor melting of the antarctic ice sheet appears to have continued throughout the late holocene differential observations of the late holocene sea level change recorded at sites in the same region are particularly useful for estimating parameters describing the earth s non elastic response to surface loading the effective parameters used here are a lithospheric thickness an upper mantle viscosity and a lower mantle viscosity describing the response below 670 km depth with the observations used here it is not possible to separate the lithospheric thickness h from the upper mantle viscosity and the viscosity results are based on the assumption that 50 h 100 km neither do these observations provide a resolution of the depth dependence of viscosity in the upper mantle and the resulting estimates are effective parameters only differential sea levels along continental margins and along the shores of large gulfs and bays constrain the effective upper mantle viscosity to be about 1 2 1020 pa s 1 while differential values from islands of different sizes are suggestive of a somewhat lower value the lower mantle taken to be below 670 km depth viscosity is about two orders of magnitude greater than this the estimated ice and rheological models explain many of the holocene sea level observations throughout the australian and southern pacific region the tilting of continental margins as exemplified by observations of variable amplitudes of the holocene high stands and the variable times at which sea levels first reached their present level along the north queensland coast and great barrier reef is well represented by these models differential holocene sea levels observed along the narrow spencers gulf of south australia are also well explained by the models and in neither case is it necessary to invoke tectonic motions predicted late holocene sea levels at small to medium sized islands are characterized by small amplitude high stands that reached their maximum values about 4000 2000 yr ago consistent with observations from the society cook and tuamotu islands

palaeoenvironmental change in tropical australasia over the last 30 000 years a synthesis by the oz intimate group the tropics are the major source of heat and moisture for the australasian region determining the tropics response over time to changes in climate forcing mechanisms such as summer insolation and the effects of relative sea level on exposed continental shelves during the last glacial period is an ongoing process of re evaluation we present a synthesis of climate proxy data from tropical australasia spanning the last 30 000 years that incorporates deep sea core coral speleothem pollen charcoal and terrestrial sedimentary records today seasonal variability is governed largely by the annual migration of the inter tropical convergence zone itcz influencing this region most strongly during the austral summer however the position of the itcz has varied through time towards the end of marine isotope stage mis 3 conditions were far wetter throughout the region becoming drier first in the south universally cooler land and sea surface temperature sst were characteristic of the last glacial maximum with drier conditions than previously although episodic wet periods are noted in the fluvial records of northern australia the deglacial period saw warming first in the coral sea and then the indonesian seas with a pause in this trend around the time of the antarctic cold reversal c 14 5 ka coincident with the flooding of the sunda shelf wetter conditions occurred first in indonesia around 17 ka and northern australia after 14 ka the early holocene saw a peak in marine sst to the northwest and northeast of australia modern vegetation was first established on indonesia then progressively south and eastward to ne australia flores and the atherton tablelands show a dry period around 11 6 ka steadily becoming wetter through the early holocene the mid late holocene was punctuated by millennial scale variability associated with the el nino southern oscillation this is evident in the marine coral speleothem and pollen records of the region

mid holocene sea surface conditions and riverine influence on the inshore great barrier reef we present measurements of sr ca 18o and spectral luminescence ratios g b from a mid holocene porites sp microatoll recovered from the nearshore great barrier reef gbr these records were used as proxies to reconstruct sea surface temperature sst the 18o of surrounding seawater 18osw and riverine influence respectively and compared with records from a modern porites sp microatoll growing in the same environment strong riverine influence in the mid holocene record is indicated by 1 an increased annual 18osw range in the mid holocene record 2 negative peaks in 18o characteristic of flood events and 3 a higher g b luminescence ratio seasonal cycles in g b suggest that humic acid inputs were elevated for a longer portion of the year during the mid holocene the seasonal cycle of 18osw peaked earlier in the year in the mid holocene record relative to the modern while mean 18osw values from the mid holocene record were similar to modern values these records provide an insight into the oceanographic conditions the nearshore gbr experienced during mid holocene climatic shifts and are consistent with a strong australian indonesian summer monsoon aism system at 4700 cal yr bp

massive siliciclastic discharge to slopes of the great barrier reef platform during sea level transgression constraints from sediment cores between 15 s and 16 s latitude and possible explanations abstract the northeast australian continental margin including the great barrier reef gbr platform provides an outstanding modern analogue for understanding sedimentation in tropical mixed siliciclastic carbonate depositional systems previous studies of cores from this margin have suggested that in contrast to widely accepted models maximum siliciclastic fluxes to slopes over the last 30 ky occurred when sea level transgressed the shelf ca 11 7 ka rather than when sea level was at a lowstand before 18 ka however climate and bathymetry can affect regional sediment deposition significantly and the cores examined to date have come from the southern queensland trough where the margin has a wet tropical climate and a broad shelf 50 km with gradual slopes in this study we examine the abundance and accumulation of siliciclastic material in four cores from lower slopes of the northern queensland trough where rivers drain a drier region and debouche onto a narrow shelf with steep incised slopes similar to previously examined cores all cores contain a dark greyish brown horizon within the upper few meters this horizon represents a low in carbonate content and corresponding high in siliciclastic material primarily clay and oxygen isotope stratigraphy shows that it was deposited during late transgression nominally between 11 and 7 ka moreover mass accumulation rate calculations demonstrate that this horizon reflects a significant rise in siliciclastic fluxes when combined with the previous work to the south it appears that slopes all along a large portion of the northeast australian continental margin received greatly enhanced inputs of siliciclastic material during late transgression independent of proximal climate and bathymetry two general explanations are offered for this observation 1 climate change induced highly variable riverine discharge over the past 30 ky with a prominent maximum coincident with late transgression or 2 the shelf stores large quantities of siliciclastic sediment during lowstand and releases this material to the slope during late transgression in either case siliciclastic accumulation on the northeast australia continental margin behaves completely opposite to predictions from conventional models

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

large variations in the holocene marine radiocarbon reservoir effect reflect ocean circulation and climatic changes accurate radiocarbon dating of marine samples requires knowledge of the marine radiocarbon reservoir effect this effect for a particular site region is generally assumed constant through time when calibrating marine 14c ages however recent studies have shown large temporal variations of several hundred to a couple of thousand years in this effect for a number of regions during the late quaternary and holocene here we report marine radiocarbon reservoir correction r r for heron reef and moreton bay in southwestern sw pacific for the last 8 ka derived from 14c analysis of 230th dated corals most of our r r for the last 5 4 ka agree well with their modern value but large r r variability of 410 yr from trough to peak with possible decadal centennial fluctuations is evident for the period 5 4 8 ka the latter time interval also has significant variations with similar features in previously published r r values for other sites in the pacific including southern peru northern chile in southeastern se pacific the south china sea vanuatu and papua new guinea with the largest magnitude of 920 yr from se pacific the mechanisms for these large r r variations across the pacific during the mid holocene are complex processes involving 1 changes in the quantity and 14c content of upwelled waters in tropical east pacific tep frequency and intensity of ocean upwelling in the tep and contribution of subantarctic mode water to the upwelled waters which is influenced by the intensity and position of southern westerly winds and 2 variations in ocean circulation associated with climate change la nina el nino conditions intensity of easterly trade winds positions of the intertropical convergence zone and the south pacific convergence zone which control the spreading of the older upwelled surface waters in the tep to the western sites our results imply the need for employing temporal changes in r r values instead of constant modern values for age calibration of holocene marine samples not only for the sw pacific sites but also for other tropical and subtropical sites in the pacific

suppression of el nino during the mid holocene by changes in the earth s orbit a number of recent reports have interpreted paleoproxy data to describe the state of the tropical pacific especially changes in the behavior of the el nino southern oscillation enso over the holocene these interpretations are often contradictory especially for the eastern tropical pacific and adjacent areas of south america here we suggest a picture of the mid holocene tropical pacific region which reconciles the data enso variability was present throughout the holocene but underwent a steady increase from the mid holocene to the present in the mid holocene extreme warm el nino events were smaller in amplitude and occurred less frequently about a mean climate state with a cold eastern equatorial pacific and largely arid coastal regions as in the present climate this picture emerges from an experiment in which a simple numerical model of the coupled ocean atmosphere system in the tropical pacific was driven by orbital forcing we suggest that the observed behavior of the tropical pacific climate over the mid to late holocene is largely the response to orbitally driven changes in the seasonal cycle of solar radiation in the tropics which dominates extratropical influences

mid late holocene sea level variability in eastern australia a re analysis of sea level data from eastern australia based on 115 calibrated c 14 ages is used to constrain the origin timing and magnitude of sea level change over the last 7000 years we demonstrate that the holocene sea level highstand of 1 0 1 5 m was reached 7000 cal yr bp and fell to its present position after 2000 yr bp these findings are in contrast to most previous studies that relied on smaller datasets and did not include the now common conversion of conventional c 14 ages to calendar years during this 5000 year period of high sea level growth hiatuses in oyster beds and tubeworms and lower elevations of coral microatolls are interpreted to represent short lived oscillations in sea level of up to 1 m during two intervals beginning c 4800 and 3000 cal yr bp the rates of sea level rise and fall 1 2 mm yr 1 during these centennial scale oscillations are comparable with current rates of sea level rise the origin of the oscillations is enigmatic but most likely the result of oceanographic and climatic changes including wind strengths ice ablation and melt water contributions of both greenland and antarctic ice sheets

evidence for stronger el nino southern oscillation enso events in a mid holocene massive coral we present a 47 year long record of sea surface temperature sst derived from sr ca and u ca analysis of a massive porites coral which grew at 4150 calendar years before present b p in vanuatu southwest tropical pacific ocean mean sst is similar in both the modern instrumental record and paleorecord and both exhibit el nino southern oscillation enso frequency sst oscillations however several strong decadal frequency cooling events and a marked modulation of the seasonal sst cycle with power at both enso and decadal frequencies are observed in the paleorecord which are unprecedented in the modern record

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

post glacial evolution of the indo pacific warm pool and el nino southern oscillation recent research has revealed new insights into the temperature size and variability of the indo pacific warm pool ipwp and the nature of the el nino southern oscillation enso since the last glacial maximum lgm sea surface temperature sst reconstructions from foraminiferal mg ca alkenone and revised coral sr ca palaeothermometry agree that ssts in the ipwp during the lgm were similar to 3degreesc cooler than at present in the central portion of the ipwf the rapid post glacial rise in sst led the deglaciation by similar to 3000 years to produce near modern ssts by the early holocene in contrast further west and north post glacial shifts in ssts in the south china and sulu seas are synchronous with abrupt climate changes in the north atlantic new evidence for the nature of the little ice age in the tropics has been obtained from a 420 year record of coral sr ca and 6180 from the great barrier reef australia this indicates that ssts and salinity were higher in the 18th century than in the 20th century the results suggest that the tropical pacific played a role as a source region of water vapour during the global expansion of little ice age glaciers the onset of modern enso periodicities is identified by palaeo enso records throughout the tropical pacific region similar to 5000 years ago with an abrupt increase in enso magnitude similar to 3000 years ago individual enso events recorded by corals reveal that the precipitation response to el nino temperature anomalies was subdued in the mid holocene the apparent non linear onset of enso in the late holocene appears to reflect abruptly enhanced interaction between the southern oscillation and the pacific intertropical convergence zone comparisons of precipitation variability recorded by great barrier reef corals with enso indices for the last 350 years confirms that non stationarity of enso teleconnections is a natural characteristic of modern climate c 2003 elsevier ltd and inqua all rights reserved

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

holocene development of three isolated carbonate platforms belize central america abstract locally operating factors such as topography of the reef basement and exposure to waves and currents rather than regionally effective factors such as the post glacial sea level rise in the western atlantic explain the different holocene developments of the three isolated carbonate platforms glovers reef lighthouse reef and turneffe islands offshore belize a series of nne striking tilted fault blocks at the passive continental margin forms the deep basement of the belize reefs glovers and lighthouse reefs are located on the same fault block while turneffe islands is situated west of lighthouse reef on an adjacent fault block the three platforms are surrounded by deep water and have surfacebreaking reef rims significant differences exist between platform interiors glovers reef has only 0 2 of land and an 18 m deep well circulated lagoon with over 800 patch reefs lighthouse reef has 3 of land and a well circulated lagoon area patch reefs are aligned along a nne striking trend that separates a shallow western 3 m and a deeper eastern 8 m lagoon turneffe islands has 22 of land that is mainly red mangrove interior lagoons are up to 8 m deep and most have restricted circulation and no patch reefs surface sediments are rich in organic matter in contrast the northernmost part of turneffe islands has no extensive mangrove development and the well circulated lagoon area has abundant patch reefs holocene reef development was investigated by means of 9 rotary core holes that all reached pleistocene reef limestones and by radiometric dating of corals maximal holocene reef thickness reaches 11 7 m on glovers reef 7 9 m on lighthouse reef and 3 8 m on turneffe islands factors that controlled holocene reef development include the following 1 holocene sea level the margin of glovers reef was flooded by the rising holocene sea ca 7500 ybp that of lighthouse reef ca 6500 ybp and that of turneffe islands between 5400 and 4750 ybp all investigated holocene reefs belong to the keep up type even though the three platforms were flooded successively and hence the reefs had to keep pace with different rates of sea level rise 2 pre holocene topography pleistocene elevation and relief are different on the three platforms this is the consequence of both tectonics and karst different elevations caused successive reef initiation and they also resulted in differences in lagoon depths variations in pleistocene topography also explain the different facies distribution patterns on the windward platforms that are located on the same fault block on lighthouse reef tectonic structures are clearly visible such as the linear patch reef trend that is aligned along a pleistocene fault on glovers reef only short linear trends of patch reefs can be detected because the pleistocene tectonic structures are presumably masked by the higher holocene thickness the lower pleistocene elevation on glovers reef is probably a consequence of both a southward tectonic tilt and stronger karstification towards the south related to higher rainfall 3 exposure to waves and currents glovers reef lighthouse reef and the northernmost part of turneffe islands receive the maximum wave force as they are open to the caribbean sea adjacent lagoons are well circulated and have luxuriant patch reef growth and no extensive mangrove development by contrast most of turneffe islands is protected from the open caribbean sea by lighthouse reef to the east and is only exposed to reduced wave forces allowing extensive mangrove growth in these protected areas