late pleistocene and holocene subtropical vegetation dynamics recorded in perched lake deposits on fraser island queensland australia abstract the dune system of fraser island in subtropical queensland australia contains numerous perched lakes with organic rich sediments these lakes are located in the subtropics and their water levels are strongly influenced by precipitation the lakes act as natural rainfall gauges which make them highly sensitive to environmental change paleoecological and paleoclimatological investigations are performed on sediment cores from lake allom a small perched lake on central fraser island a detailed chronology is based on a series of closely spaced ams radiocarbon dates supplemented with sedimentological information based on extrapolation the chronology indicates an age range from 56 14c kyr bp to present with a major hiatus occurring during the last glacial maximum pollen analysis of the lake allom sediment record reveals strong changes between rainforest and open woodland vegetation the holocene portion of the record shows a stepwise vegetation development from dry conditions in the early holocene to high lake levels and increasing forest between 5 5 and 3 cal kyr bp at 3 2 cal kyr bp a large diversification occurred towards the present day heterogeneous sub tropical rainforest vegetation followed by a small rainforest decline at 0 45 cal kyr bp additionally charcoal analysis indicates increases in fire occurrence contemporaneously with periods of drier vegetation and or low lake levels part of the reconstructed vegetation changes can be related to local and regional factors including forest succession dune formation sea level rise and human impact comparison with paleoclimate records from tropical and temperate regions indicates that the temporal and spatial dynamics of vegetation changes in eastern australia are primarily controlled by climate variability particularly the increasing activity of the el nino southern oscillation enso during the late holocene caused greater climate variability in eastern australia resulting in more heterogenous vegetation cover

diagenesis and geochemistry of porites corals from papua new guinea implications for paleoclimate reconstruction coral proxy records of sea surface temperature sst and hydrological balance have become important tools in the field of tropical paleoclimatology however coral aragonite is subject to post depositional diagenetic alteration in both the marine and vadose environments to understand the impact of diagenesis on coral climate proxies two mid holocene porites corals from raised reefs on muschu island papua new guinea were analysed for sr ca 18 o and 13 c along transects from 100 aragonite to 100 calcite thin section analysis showed a characteristic vadose zone diagenetic sequence beginning with leaching of primary aragonite and fine calcite overgrowths transitional to calcite void filling and neomorphic fabric selective replacement of the coral skeleton average calcite sr ca and 18 o values were lower than those for coral aragonite decreasing from 0 0088 to 0 0021 and 5 2 to 8 1 respectively the relatively low sr ca of the secondary calcite reflects the sr ca of dissolving phases and the large difference between aragonite and calcite sr ca partition coefficients the decrease in 18 o of calcite relative to coral aragonite is a function of the 18 o of precipitation carbon isotope ratios in secondary calcite are variable though generally lower relative to aragonite ranging from 2 5 to 10 4 the variability of 13 c in secondary calcite reflects the amount of soil co 2 contributing 13 c depleted carbon to the precipitating fluids diagenesis has a greater impact on sr ca than on 18 o the calcite compositions reported here convert to sst anomalies of 115 c and 14 c respectively based on calcite sr ca compositions in this study and in the literature the sensitivity of coral sr ca sst to vadose zone calcite diagenesis is 1 1 to 1 5 c per percent calcite in contrast the rate of change in coral 18 o sst is relatively small 0 2 to 0 2 c per percent calcite we show that large shifts in 18 o reported for mid holocene and last interglacial corals with warmer than present sr ca ssts cannot be caused by calcite diagenesis low level calcite diagenesis can be detected through x ray diffraction techniques thin section analysis and high spatial resolution sampling of the coral skeleton and thus should not impede the production of accurate coral paleoclimate reconstructions copyright 2003 elsevier science ltd

persistent solar influence on north atlantic climate during the holocene surface winds and surface ocean hydrography in the subpolar north atlantic appear to have been influenced by variations in solar output through the entire holocene the evidence comes from a close correlation between inferred changes in production rates of the cosmogenic nuclides carbon 14 and beryllium 10 and centennial to millennial time scale changes in proxies of drift ice measured in deep sea sediment cores a solar forcing mechanism therefore may underlie at least the holocene segment of the north atlantic9s 1500 year cycle the surface hydrographic changes may have affected production of north atlantic deep water potentially providing an additional mechanism for amplifying the solar signals and transmitting them globally

new insights into the structure of the south caspian basin from seismic reflection data gorgan plain iran this research presents an integrated study of 2d seismic reflections and calibrated well data to outline the structural development of the gorgan plain on the border of the south caspian hydrocarbon basin in the alborz and kopeh dagh ranges of northeast iran eight seismic horizons including two unconformities have been identified ranging in age from early jurassic to quaternary analysis and interpretation of geophysical data provide an understanding of the structural geology of the gorgan plain crucial for investigation of structural traps seismic interpretation indicates structural features such as deep reverse listric faults inverted normal faults for older formations strike slip and normal faults in younger sequences dome and basin interference patterns of folding for all the top formations well data demonstrate the occurrence of a disconformity at the base of upper cretaceous beds and an angular unconformity at the base of paleogene evidence identified in well and seismic reflection data proves a complex pattern of tectonic phases since the early jurassic it seems reasonable to suppose that these structural patterns are related to a change in direction of tectonic compression which in turn has produced structural hydrocarbon traps in crests of domes in the gorgan area

the early holocene sea level rise the causes anatomy and consequences of the early holocene sea level rise ehslr are reviewed the rise of ca 60m took place over most of the earth as the volume of the oceans increased during deglaciation and is dated at 11 650 7000 cal bp the ehslr was largely driven by meltwater release from decaying ice masses and the break up of coastal ice streams the patterns of ice sheet decay and the evidence for meltwater pulses are reviewed and it is argued that the ehslr was a factor in the ca 8470 bp flood from lake agassiz ojibway patterns of relative sea level changes are examined and it is argued that in addition to regional variations temporal changes are indicated the impact of the ehslr on climate is reviewed and it is maintained that the event was a factor in the 8200 bp cooling event as well as in changes in ocean current patterns and their resultant effects the ehslr may also have enhanced volcanic activity but no clear evidence of a causal link with submarine sliding on continental slopes and shelves can yet be demonstrated the rise probably influenced rates and patterns of human migrations and cultural changes it is concluded that the ehslr was a major event of global significance knowledge of which is relevant to an understanding of the impacts of global climate change in the future

sediment water interaction acidity and other water quality parameters in a subtropical setting pimpama river southeast queensland the geological setting and landuse activities of the pimpama river catchment are typical for many drainage systems in southeast queensland the river originates in coastal ranges of late paleozoic age crosses a floodplain developed during the late pleistocene holocene sea level fluctuations and flows into the southern part of the moreton bay the formation of sedimentary pyrite associated with the mid holocene transgression is an important feature of this coastal setting the oxidation and hydrolysis of pyrite and the consequent production of sulfuric acid are controlled by the amount and seasonality of rainfall and influenced locally by landuse activities the acid production and the leaching of dissolved metals from river alluvium and estuarine sediments impact substantially on land and aquatic habitats the water quality of the pimpama river and its tributaries reflects the lithology of the bedrock and can vary largely depending on season tidal regimes sediment lithology local topography and agricultural activities

holocene temperature records show millennial scale periodicity past studies have detected an 1500 year climate cycle in various types of pleistocene geologic or ice deposits it has been proposed that a 1470 year cycle fits the pleistocene dansgaard oeschger do oscillations and can be explained by a threshold model with forcing we used nine temperature reconstructions to see if this cycle exists during the holocene all these data sets except greenland holocene data can be fit by models close to a 1470 year period or are compatible to such a model or can be fit by cycles near 1200 years both of which can be related to solar forcing these results lend support to the nonlinear threshold model for initiation of pleistocene do events and suggest that this periodic climate signal has continued into the holocene but with reduced magnitude

local magnitude tomography in california lateral variation in crustal attenuation of california is calculated by inverting 25 330 synthetic wood anderson amplitudes from the california integrated seismic network cisn for site source and path effects two dimensional attenuation q or 1 q is derived from the path term which is calculated via an iterative least squares inversion that also solves for perturbations to the site and source terms source terms agree well with initial cisn m l s and site terms agree well with a prior regression analysis q ranges from low attenuation at 0 001 q 1000 to high attenuation at 0 015 q 66 with an average of 0 07 q 143 the average q is consistent with an amplitude decay function log a for california when q is combined with a simple geometrical spreading rate attenuation in california is consistent with the tectonic structure of california with low attenuation in the sierra batholith and high attenuation at the geysers at long valley and in the salton trough possibly due to geothermal effects also path terms are an order of magnitude smaller than site and source terms suggesting that they are not as important in correcting for m l

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 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

oscillations in the southern extent of the indo pacific warm pool during the mid holocene the indo pacific warm pool ipwp is thought to play a key role in the propagation and amplification of climate changes through its influence on the global distribution of heat and water vapour however little is known about past changes in the size and position of the ipwp in this study we use a total of 48 modern and fossil coral records from the mentawai islands sumatra indonesia and muschu koil islands papua new guinea to reconstruct oscillations in the extent of the ipwp since the mid holocene we show that reliable estimates of mean sea surface temperature sst can be obtained from fossil corals by using low resolution sr ca analysis of a suite of corals to overcome the large uncertainties associated with mean sr ca sst estimates from individual coral colonies the coral records indicate that the southeastern and southwestern margins of the ipwp were cooler than at present between similar to 5500 and 4300 years bp similar to 1 2 degrees c 0 3 degrees c and were similarly cool before similar to 6800 years bp this mid holocene cooling was punctuated by an abrupt short lived shift to mean ssts that were warmer than at present between similar to 6600 and 6300 years bp similar to 1 3 degrees c 0 3 degrees c while similarly warm conditions may have also existed after similar to 4300 years bp we suggest that mid holocene cooling at our study sites was related to contractions of the southeastern and southwestern margins of the ipwp associated with the more northerly position of the inter tropical convergence zone itcz that accompanied mid holocene strengthening of the asian summer monsoon conversely intervals of abrupt warming appear to correspond with widespread episodes of monsoon weakening and accompanying southward migrations of the itcz that caused the ipwp to expand beyond our coral sites intervals of a strengthened asian monsoon and cooling in the southwestern ipwp during the mid holocene appear to correspond with a more positive indian ocean dipole iod like mean configuration across the tropical indian ocean suggesting that the asian monsoon iod interaction that exists at interannual time scales also persists over centennial to millennial scales associated mean changes in the pacific enso modes may have also occurred during the mid holocene the dynamic and inter connected behaviour of the ipwp with tropical climate systems during the mid holocene highlights the fundamental importance of the warm pool region for understanding climate change throughout the tropics and beyond c 2009 elsevier ltd all rights reserved

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

diagenesis and its impact on sr ca ratio in holocene acropora corals the effect of early diagenesis on sr ca ratios encapsulated in coral skeletons was evaluated by comparing mineralogical structural and geochemical characteristics of modern and holocene branching acropora colonies the modern specimens acropora danai acropora formosa come from reunion island western indian ocean and the great barrier reef of australia respectively the sr ca ratios of modern specimens range from 9 08 to 9 37 mmol mol the fossil acroporids acropora group danai robusta were collected from a 50 m core drilled through a barrier reef in tahiti island their c 14 ages range from 3 200 to 10 200 calendar years b p fossil skeletons are 100 aragonite earlier diagenesis has occurred in the marine environment it is expressed by growth of secondary inorganic aragonite over primary skeletal aragonite needles development of syntaxial aragonite cements within intraskeletal cavities and decrease in size of original 1 1 050 m wide pores residual porosity ranges from 25 to 28 which results in a volume reduction by 34 to 49 cementation increases with increasing age of the corals later diagenesis has occurred in a mixed marine freshwater environment it includes partial dissolution of skeletal and growth of cement aragonite fibres in the form of spherolites irregular meshes of large squarely terminated laths this results in an increase in porosity from 30 to 59 by reference to modern well preserved acroporids this diagenetic alteration has led to an increase of sr ca values from 9 08 9 37 to 8 89 10 55 mmol mol this variation in sr ca ratio can be linked to the increase in the amount of sr enriched cements relative to the volume of the skeletal aragonite and to a more homogeneous distribution of these cements throughout the skeleton the uncritical use of sr ca ratios as paleothermometers from diagenetically altered skeletons may cause serious misinterpretations accordingly estimate of the degree of diagenetic alteration in skeletons is a prerequisite to any paleoclimatic reconstruction based on coral records

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

predicted and observed holocene sea levels on the australian coast what do they indicate about hydro isostatic models in far field sites data relating to holocene sea level elevations and ages obtained by radiocarbon dating of relict calcareous skeletons of intertidal organisms from widely spaced parts of the australian coast a far field region of comparative tectonic stability are divisible into two sets namely pre and post ca 3600 yr bp the older ages are from material consistently between 1 5 m and 2 2 m higher than present sea level whereas the younger ages ca 3600 1500 yr bp generally cluster around 1 m above present sea level the elevations do not display any decline in amplitude from north to south over an extensive transect contrary to predictions by hydro isostatic models also there appears to be little difference between time elevation results for the coasts of north queensland new south wales and the bass strait region adjacent to tasmania despite differences in the width of the continental shelf in these three locations and the expectation of some hydro isostatic warping of the continental shelf subsequent to the onset of the holocene transgression results from the south and southwest coasts of western australia also display similar elevations to the east coast for the same time periods there is sufficient evidence extending over 20 of latitude to suggest that north south differences related to hydro isostatic influence is limited or non existent there is insufficient data to test hydro isostatic models across continental shelves hydro isostasy and the lithological elasticity it reflects may not be as pronounced in far field sites with narrow continental shelves as models predict stable far field passive continental margins may be the best place to measure the ratio of inputs of eustatic and hydro isostatic influences on holocene relative sea levels copyright 2002 john wiley sons ltd journal of quaternary science

testing models of mid to late holocene sea level change north queensland australia understanding the nature of global ice equivalent eustatic sea level changes during the mid to late holocene is important to our understanding of how ice sheets will respond to future climate change this study re analyses the indicative meaning and age control of existing relative sea level rsl data from cleveland bay north queensland australia and presents new rsl data from a foraminifera based transfer function as a preliminary test of global geophysical models in this region during the mid to late holocene the foraminifera based transfer function produces reliable rsl estimates consistent through the mid to late holocene at different locations in cleveland bay analysis of the combined rsl database reveals that rsl rose above present between 8 and 6 2 ka cal bp with the peak of the sea level highstand c 2 8 m above present at c 5 ka cal bp remaining relatively stable above 1 5 m from 6 2 until at least 2 3 ka cal bp falling to present in the last millennia this long period of sea level above present in the mid to late holocene suggests a gradual rather than abrupt end to global ice melt which must have continued into the late holocene this new analysis also shows no evidence for episodic fluctuations within the highstand although they cannot be entirely ruled out by this study this study demonstrates that more sea level data needs to be collected from locations uncontaminated by glacio isostasy hydro isostasy and tectonic effects in order to better constrain the late holocene melt histories of the large polar ice sheets

calcite filled borings in the most recently deposited skeleton in live collected porites scleractinia implications for trace element archives abstract skeletons of the scleractinian coral porites are widely utilized as archives of geochemical proxies for among other things sea surface temperature in paleoclimate studies here we document live collected porites lobata specimens wherein as much as 60 of the most recently deposited skeletal aragonite i e the part of the skeleton that projects into the layer of living polyps and thus is still in direct contact with living coral tissue has been bored and replaced by calcite cement calcite and aragonite were identified in situ using raman microspectroscopy the boring filling calcite cement has significantly different trace element ratios sr ca mmol mol 6 3 1 4 mg ca mmol mol 12 0 5 1 than the host coral skeletal aragonite sr ca mmol mol 9 9 1 3 mg ca mmol mol 4 5 2 3 the borings appear to have been excavated by a coccoid cyanobacterium that dissolved aragonite at one end and induced calcite precipitation at the other end as it migrated through the coral skeleton boring activity and cement precipitation occurred concomitantly with coral skeleton growth thus replacing skeletal aragonite that was only days to weeks old in some cases although the cement filled borings were observed in only 20 of sampled corals their occurrence in some of the most recently produced coral skeleton suggests that any corallum could contain such cements irrespective of the coral s subsequent diagenetic history in other words pristine skeletal aragonite was not preserved in parts of some corals for even a few weeks although not well documented in coral skeletons microbes that concomitantly excavate carbonate while inducing cement precipitation in their borings may be common in the ubiquitous communities that carry out micritization of carbonate grains in shallow carbonate settings thus such phenomena may be widespread and failure to recognize even very small quantities of early cement filled borings in corals used for paleoclimate studies could compromise high resolution paleotemperature reconstructions the inability to predict the occurrence of cement filled borings in coralla combined with the difficulty in recognizing them on polished blocks highlights the great care that must be taken in vetting samples both for bulk and microanalysis of geochemistry

inter tidal fixed indicators of former holocene sea levels in australia a summary of sites and a review of methods and models abstract the reconstruction of mid to late holocene marine environments using the calcareous remains of inter tidal fixed biological indicators as sea level proxies is reviewed useful palaeo environmental information can be obtained from the fossil evidence of successive invasions and disappearances of tropical and temperate species within the sub fossil inter tidal biological sequences examples illustrating spatially synchronous late holocene sea level fluctuations are described from 3000 km of north south coastline along eastern australia the method uses tightly constrained species such as the tubeworm galeolaria caespitosa which allows for the precise measurement of relative sea level fluctuations by using the differential between emerged sub fossil encrustations and current distributions of the same species the error range can be defined according to the extent of preservation of the relic distributions particularly the extent that diagnostic boundaries between species limited to different inter tidal zones have been preserved the rapidity of sea level fluctuations is inferred by the preservation from erosion of emerged shell layers as well as discontinuities in the relic biological sequences and the relative preservation of fragile species this apparent rapidity of sea level fluctuations as well as evidence of near uniform synchronous sea level heights along the north south span of the entire australian coast and equally consistent variations australia wide in spencer gulf and rottnest island raises questions about the predicted poleward decline of sea level curves derived from hydro isostatic rebound modelling

global monsoons in the mid holocene and oceanic feedback the response of the six major summer monsoon systems the north american monsoon the northern africa monsoon the asia monsoon the northern australasian monsoon the south america monsoon and the southern africa monsoon to mid holocene orbital forcing has been investigated using a coupled ocean atmosphere general circulation model foam with the focus on the distinct roles of the direct insolation forcing and oceanic feedback the simulation result is also found to compare well with the ncar csm the direct effects of the change in insolation produce an enhancement of the northern hemisphere monsoons and a reduction of the southern hemisphere monsoons ocean feedbacks produce a further enhancement of the northern africa monsoon and the north american monsoon however ocean feedbacks appear to weaken the asia monsoon although the overall effect direct insolation forcing plus ocean feedback remains a strengthened monsoon the impact of ocean feedbacks on the south american and southern african monsoons is relatively small and therefore these regions especially the south america experienced a reduced monsoon regime compared to present however there is a strong ocean feedback on the northern australian monsoon that negates the direct effects of orbital changes and results in a strengthening of austral summer monsoon precipitation in this region a new synthesis is made for mid holocene paleoenvironmental records and is compared with the model simulations overall model simulations produce changes in regional climates that are generally consistent with paleoenvironmental observations

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

microatoll record for large century scale sea level fluctuations in the mid holocene coral microatolls have been long used as precise indicators of past sea level but their use for precise definition of detailed sea level fluctuations is still rare here we report twelve high precision thermal ionization mass spectrometric th 230 ages for twelve rims of five mid holocene microatolls from all emerged reef terrace at leizhou peninsula northern south china sea this is a tectonically stable area enabling lis to reconstruct both the timing and trajectory of local sea level fluctuations accurately the elevations of these microatoll rims and cores were accurately determined relative to the surface of modern livin microatolls at the same site the results indicate that the sea level during the period of 7050 6600 yr bp years before ad 1950 was about 171 to 219 cm above the present with at least four cycles of fluctuations over this 450 yr interval sea level fluctuated by 20 40 cm on century scales crown copyright c 2009 published by university of washington all rights reserved

oxygen isotopes sea level changes and the temperature history of a coral reef environment in new guinea over the last 105 years abstract coral reef terraces consisting of an upward succession of fringing and barrier reef types are preserved on land along the raising coast of huon peninsula new guinea seven coral reef units i vii from the coast landwards spaced at about 20 kyr interval provide a rather complete record of sea levels oxygen isotopes and temperature of teh surface tropical ocean over the duration of the high sea level events of the last glacial cycle the systematic sampling of the coral reefs was restricted to the massive tridacna gigas species the giant clam which are about 0 7 0 enriched in 18o relative to calcite equilibrium value and the presence of symbionts seems to have no effect on the 18o of their aragonitic skeleton sea levels rose rapidly to 5 6 5 m above present during the last interglacial which on stratigraphic grounds and 18o compositions can be separated into an early phase whose 18o is similar to modern reef viia dated at 138 kyr and a late phase that is 0 6 0 heavier reef viib dated at 118 kyr fringing reefs vi v iv iii and ii record short lived high sea levels stands at 107 85 60 45 to 40 and 31 kyr respectively that stopped short of the present sea level 12 19 28 32 to 42 m the general decline of the high sea level stands corresponds to an average 18o enrichment of 1 7 0 measured between the early interstadials of isotope stage 5 vi and v and the late interstadials of isotope stage 3 iv iiia iiib and ii the maximum 18o enrichment of 1 7 0 relative to present was registered during a regressive phase of reef iiia stratigraphic evidence indicates that sea level lows in the range of 37 to 55 m below present have occurred in between the high sea level stands but those are unlikely to represent the lowest sea levels of the last glacial cycle sea levels and 18o ddta pair offer important clues regarding the partitioning of ice volume and temperature in 18o records the results suggest that the ice volume effect accounts for the observed 18o changes during the early interstadial culminations but only for 29 46 during the late interstadial culminations sea water cooling beyond the threshold limit of coral reef growth 18 c did not occur during the last glacial cycle the temperature of the surface tropical ocean was similar to present during the early interstadials of isotope stage 5 and cooler by 3 c below present during the later interstadials of isotope stage 3

palaeoenvironmental records from fossil corals the effects of submarine diagenesis on temperature and climate estimates the geochemistry of coral skeletons may reflect seawater conditions at the time of deposition and the analysis of fossil skeletons offers a method to reconstruct past climate however the precipitation of cements in the primary coral skeleton during diagenesis may significantly affect bulk skeletal geochemistry we used secondary ion mass spectrometry sims to measure sr mg b u and ba concentrations in primary coral aragonite and aragonite and calcite cements in fossil porites corals from submerged reefs around the hawaiian islands cement and primary coral geochemistry were significantly different in all corals we estimate the effects of cement inclusion on climate estimates from drilled coral samples which combine cements and primary coral aragonite secondary 1 calcite or not vert similar2 aragonite cement contamination significantly affects sr ca sst estimates by 1 c and 0 4 to 0 9 c respectively cement inclusion also significantly affects mg ca b ca and u ca sst estimates in some corals x ray diffraction xrd will not detect secondary aragonite cements and significant calcite contamination may be below the limit of detection not vert similar1 of the technique thorough petrographic examination of fossils is therefore essential to confirm that they are pristine before bulk drilled samples are analysed to confirm that the geochemistry of the original coral structures is not affected by the precipitation of cements in adjacent pore spaces we analysed the primary coral aragonite in cemented and uncemented areas of the skeleton sr ca b ca and u ca of primary coral aragonite is not affected by the presence of cements in adjacent interskeletal pore spaces i e the coral structures maintain their original composition and selective sims analysis of these structures offers a route to the reconstruction of accurate ssts from altered coral skeletons however mg ca and ba ca of primary coral aragonite are significantly higher in parts of skeletons infilled with high mg calcite cement we hypothesise this reflects cement infilling of intraskeletal pore spaces in the primary coral structure

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

mid holocene sea level and coral reef demise u th dating of subfossil corals in moreton bay australia it is increasingly apparent that sea level data e g microfossil transfer functions dated coral microatolls and direct observations from satellite and tidal gauges vary temporally and spatially at regional to local scales thus limiting our ability to model future sea level rise for many regions understanding sealevel response at far field locations at regional scales is fundamental for formulating more relevant sea level rise susceptibility models within these regions under future global change projections fossil corals and reefs in particular are valuable tools for reconstructing past sea levels and possible environmental phase shifts beyond the temporal constraints of instrumental records this study used abundant surface geochronological data based on in situ subfossil corals and precise elevation surveys to determine previous sea level in moreton bay eastern australia a far field site a total of 64 u th dates show that relative sea level was at least 1 1 m above modern lowest astronomical tide lat from at least 6600 cal yr bp furthermore a rapid synchronous demise in coral reef growth occurred in moreton bay 5800 cal yr bp coinciding with reported reef hiatus periods in other areas around the indo pacific region evaluating past reef growth patterns and phases allows for a better interpretation of anthropogenic forcing versus natural environmental climatic cycles that effect reef formation and demise at all scales and may allow better prediction of reef response to future global change

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

seawater 234 u 238 u during the last 800 thousand years abstract constraining the history of seawater 234u 238u is important because this ratio is used to assess the validity of u th ages and because it provides information about the past rate of physical weathering on the continents this study makes use of u rich slope sediments from the bahamas in an attempt to reconstruct seawater 234u 238u for the last 800 kyr for the last 360 kyr u th dating of these sediments provides ages and initial 234u 238u values sixty seven samples largely from marine highstands have initial 234u 238u which scatter somewhat about the modern seawater value 1 145 but neither this scatter nor the average value increases with age of sample these data contrast with published coral data and suggest that seawater 234u 238u has remained within 15 of the modern value for the last 360 kyr this confirms the rejection of coral u th ages where the initial 234u 238u is significantly different from modern seawater data from older highstands dated with 18o stratigraphy or by the presence of the brunhes matuyama b m reversal at 780 kyr allow seawater 234u 238u to be assessed prior to the range of the 230th chronometer unfortunately diagenetic scatter in the data between the b m reversal and 360 kyr is rather large probably relating to low u concentrations for these samples but there is no indication of a trend in seawater 234u 238u with age high u samples from close to the b m reversal show less diagenetic scatter and an initial 234u 238u that averages 1 102 this lower value can be explained by lower seawater 234u 238u at the time of the b m reversal or by progressive loss of 234u from the sediment by recoil a simple box model is presented to illustrate the response of seawater 234u 238u to variations in riverine input such as might be caused by changes in continental weathering comparison of the bahamas 234u 238u data with model results indicates that riverine 234u 238u has not varied by more than 65 for any 100 kyr period during the last 360 kyr it also indicates that the ratio of physical to chemical weathering on the continents has not been higher than at present for any extended period during the last 800 kyr

coupled uranium isotope and sea level variations in the oceans abstract globally rivers supply uranium to the oceans with excess 234 u relative to secular equilibrium and 234 u taken up by corals can be used for dating in addition the 234 u abundance in sea water at the time the coral was growing can be measured independently the veracity of u series ages used in determining past sea level variations is dependent on selecting pristine corals free from diagenetic alteration a quantitative test for alteration assumes invariant 234 u abundances in the oceans for at least the past half a million years and results from samples outside of a narrow range in modern ocean 234 u abundance are excluded from data sets here we have used previously published data to show that 234 u in the oceans appears to be variable and directly related to changes in sea level not only over long glacial interglacial timescales but also at very short centennial timescales most of the previously discarded data can be used to provide valuable additional sea level information the process permits a unique insight into the interplay between sources and sinks of uranium in the oceans mediated by sea level changes at rates far faster than previously thought possible similar rapid sea level forcing of other trace element abundances in the oceans is likely

geomorphic evidence for mid late holocene higher sea level from southeastern australia an elevated sheltered pocket beach sequence at batemans bay nsw australia composed of shelly fine to medium grained sand provides geomorphic evidence of higher than present sea level during the mid late holocene the sequence is composed of a sand facies with variable amounts of shell and contains a number of well defined dipping reflectors identified in ground penetrating radar gpr profiles indicative of a small prograded beach system this beach succession is overlain by storm or tsunami deposits the beach deposit accumulated between 2500 and 5000 cal bp under relatively high energy conditions within a more open immature estuary during a period of higher sea level both deposits have been preserved by a low energy mangrove facies that accumulated after the recent fall in sea level cut off ocean wave activity from the area approximately 2000 2500 cal bp this beach sequence provides new evidence for a period of higher sea level 1 1 5 m higher than present that lasted until at least c 2000 2500 cal bp and adds complementary geomorphic evidence for the mid to late holocene sea level highstand previously identified along other parts of the southeast australian coast using other methods

millennial scale trends in west pacific warm pool hydrology since the last glacial maximum models and palaeoclimate data suggest that the tropical pacific climate system plays a key part in the mechanisms underlying orbital scale and abrupt climate change atmospheric convection over the western tropical pacific is a major source of heat and moisture to extratropical regions and may therefore influence the global climate response to a variety of forcing factors the response of tropical pacific convection to changes in global climate boundary conditions abrupt climate changes and radiative forcing remains uncertain however here we present three absolutely dated oxygen isotope records from stalagmites in northern borneo that reflect changes in west pacific warm pool hydrology over the past 27 000 years our results suggest that convection over the western tropical pacific weakened 18 000 20 000 years ago as tropical pacific and antarctic temperatures began to rise during the early stages of deglaciation convective activity as inferred from oxygen isotopes reached a minimum during heinrich event 1 ref 10 when the atlantic meridional overturning circulation was weak pointing to feedbacks between the strength of the overturning circulation and tropical pacific hydrology there is no evidence of the younger dryas event in the stalagmite records however suggesting that different mechanisms operated during these two abrupt deglacial climate events during the holocene epoch convective activity appears to track changes in spring and autumn insolation highlighting the sensitivity of tropical pacific convection to external radiative forcing together these findings demonstrate that the tropical pacific hydrological cycle is sensitive to high latitude climate processes in both hemispheres as well as to external radiative forcing and that it may have a central role in abrupt climate change events

speleothem derived asian summer monsoon variations in central china 54 46 ka the oxygen isotope signature delta o 18 of stalagmite si3 collected from shizi cave in north east sichuan province provides an asian summer monsoon asm record in central china for the period 54 46 ka the si3 delta o 18 record clearly shows a negative delta o 18 excursion centred around 49 4 ka which was reported in hulu cave in east china but not identified in the speleothem records from south west china as a whole this record displays a higher coherence with the two hulu records from east china than with the speleothem delta o 18 records from south west china suggesting that at 54 46 ka central china was influenced more by the east asian summer monsoon than by the indian summer monsoon it also displays a significant negative delta o 18 excursion at 47 5 46 6 ka which is not clearly documented in two other speleothem delta o 18 records previously reported from south west china this suggests that details of the greenland interstadial 12 warrant further investigations in future in monsoonal china the si3 delta o 18 record displays more significant centennial scale variations than the other four speleothem delta o 18 records from east and south west china which may be due to the fact that the study site is closer to the north west boundary of the asm and more sensitive to variations of the asm than east and south west china copyright c 2011 john wiley sons ltd

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

holocene evolution of coastal wetlands in wet tropical northeastern australia pollen in sediments drilled from the innisfail coastal plain northeast queensland australia was examined to reconstruct the evolution of holocene wetlands in a wet tropical environment in contrast to monsoonal australia stable environmental conditions created by year round rainfall and low tidal range caused abrupt unidirectional transitions in wetland zonation as marine influence changed this has enabled a detailed reconstruction of the marine transgression and subsequent progradation mangroves colonized in response to marine transgression at c 7400 bp as riverine mangroves of low salt tolerance migrated up the mulgrave river these were replaced around 7000 bp by extensive rhizophora dominated mangroves coinciding with the development of a rhizophora dominated community in wyvuri embayment mangroves reached their greatest extent as sea level rise slowed towards 6000 bp with a stillstand indicated by a brief return to terrestrial conditions at one site high freshwater input depressed salt i

holocene and late pleistocene relative sea level fluctuations along the east coast of india abstract hermatypic coral colonies and intertidal fossil bearing grainstone packstone and sandstone beds of holocene and of a late pleistocene highstand are exposed above the present high tide level htl at a number of locations along the east coast of india from cape comorin to rameswaram being a passive margin boundary free from indications of late quaternary seismogenic movements this sector provides a benchmark for defining minor relative sea level perturbations during the late pleistocene and holocene highstands along a tropical coast lying between latitudes 5 n and 10 n a series of marine terraces carved on and locally blanketted by late pleistocene biotic and terrigenous accumulations occur at different elevations up to 4 4 m above ltl at manappad point possibly signifying discrete stillstand episodes followed by abrupt intervals of rising falling sea level sea level indicators of the holocene highstand occur in this sector as well as along the fringes of the godavari delta further north the holocene highstand reached nearly 3 m above ltl at 7 3 ka remained stable for approximately 1 7 kyr and was followed by a relative sea level fall between 5 2 and 4 2 ka there was a second pulse of relative sea level rise of a few metres leading to a fresh spurt in coral growth along the northern coast of mandapam and rameswaram this was nearly contemporaneous with fresh melting of ice sheets of antarctica the little ice age lia witnessed a minor 1 m relative sea level fall along this coast resulting in rapid diagenetic hardening and infiltration of goethite into the emerged foreshore sand at karikovil and its neighbourhood this was followed by a rise of the sea level during the last few centuries

detailed history of holocene climate variability in australia from dust records in peat cores we present 8 to 10 ka long high resolution records of australian dust export extracted from peat cores in bogs from australia s snowy mountains and from new zealand the dust deposition history is reconstructed from the weight of ash after peat ignition we then determine the extended trace element chemistry on samples as small as 0 5 mg to discriminate between local sediment and far transported dust the origin of long travelled dust is established using a provenance model to fingerprint the source regions from where dust was entrained 1 2 this is achieved by matching the chemistry of dust with that from a database of samples collected from the major dust source regions in australia n 220 this is possible due to the remarkable homogeneity of trace elements within australia s many inland basins variability in the rates and sources of dust deposition through time are used to infer patterns of aridity and climate variability through the holocene in the younger layers of peat the deposition of anthropogenic aerosols also records a detailed history of european settlement in australia tracking early european development and industrialization as well as the advent of intensive agriculture

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

microatolls as sea level indicators on a mid ocean atoll microatolls are discoid corals with flat upper surfaces that develop when upward coral growth is constrained by exposure at low tide they have been widely viewed as important and relatively precise indicators of modern and paleo sea level positions because of their sensitivity to the water air interface though this has rarely been directly established by survey to a precise datum this study involved an accurate survey of 282 microatolls growing in a range of intertidal environments open reef flats interisland passages lagoons across the cocos keeling islands a mid ocean atoll in the indian ocean the upper surface elevation of modern microatolls was found to vary through more than 40 cm across the environments in which these corals occur on cocos representing more than 30 of the spring tide range much of the variation reflects subtle ponding at low water levels across extensive low gradient reef surfaces associated with interisland passages microatolls in open reef flat habitats are typically constrained within the narrowest and most consistent elevation range around the atoll the environment in which individual fossil microatolls occurred when they were alive is significant in reconstructing former sea levels

holocene sea level fluctuations inferred from the evolution of depositional environments of the southern langebaan lagoon salt marsh south africa a holocene sea level curve is constructed from the facies distribution and radiocarbon ages of sediment recovered from the distal southern salt marsh of langebaan lagoon on the southwest coast of south africa calibrated radiocarbon analyses of an oyster rich bioclastic gravel indicate that the flandrian transgression flooded the lagoon to 0 3 m above present day levels by 6750 years ago 6 8 ka organic matter and shell material dated in distal lagoonal sediments indicate that sea level returned to present day levels by 4 9 ka and have since remained within 61 m of present day levels bleached shell and a hiatus in sedimentation suggest an approximate 1 m sea level lowstand between 2 5 and 1 8 ka changes in the macrobenthos assemblage since 1 5 ka that include the loss of the oysterostrea atherstonei razor clamsolen capensis brown musselarcuatula capensis and periwinkleoxystele variegata reflect loss of hard substrate decreased tidal flow velocities as reworked sands prograded into the southern la

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

coral clues to rapid sea level change earth s climate can change substantially on time scales of 1000 years or so but given the time it takes for an ice sheet to grow or melt it has been unclear whether continental ice sheets and hence global sea levels mirror these rapid changes in his perspective henderson discusses the report by thompson and goldstein who have used a new correction method to date coral samples that are up to 250 000 years old the corals can be used to deduce past sea levels the resulting sea level record shows that sea levels have varied on millennial time scales even during times of high sea level and relative climate stability

a high precision record of mid late holocene sea level events from emergent coral pavements in the houtman abrolhos islands southwest australia early work on sea levels in southwest australia claimed to recognise a holocene sea level highstand which was not seen in better known sea level records elsewhere at the time more recent work has confirmed that a mid holocene highstand occurred about 6 kyr ago as new data on oscillating sea levels from the region have recently been published a high continuity precisely dated and accurately surveyed record was obtained from emergent coral pavements in the leeward houtman abrolhos islands serventy island a tectonically stable region from where good quality holocene sea level data have been previously obtained from corals from the mid holocene highstand ca 7 u th kyr ago sea level declined linearly during the remainder of the holocene as the carbonate platform prograded leewards hydro isostatic controls are probably significant in the record c 2005 elsevier ltd and inqua all rights reserved

the mid holocene sea level highstand at bogenfels pan on the southwest coast of namibia the radiocarbon ages of mollusc shells from the bogenfels pan on the hyper arid southern coast of namibia provide constraints on the holocene evolution of sea level and in particular the mid holocene highstand the bogenfels pan was flooded to depths of 3 m above mean sea level amsl to form a large subtidal lagoon from 7300 to 6500 calibrated radiocarbon years before present cal yr bp the mollusc assemblage of the wave sheltered lagoon includes nassarius plicatellus lutraria lutraria and the bivalves solen capensis and gastrana matadoa both of which no longer live along the wave dominated southern namibian coast the radiocarbon ages of mollusc shell from a gravely beach deposit exposed in a diamond exploration trench indicate that sea level fell to near or 1 m below its present day position between 6500 and 4900 cal yr bp the rapid emergence of the pan between 6500 and 4900 cal yr bp exceeds that predicted by glacio isostatic models and may indicate a 3 m eustatic lowering of sea level the beach deposits at bogenfels indicate that sea level rose to 1 m amsl between 4800 and 4600 cal yr bp and then fell briefly between 4600 and 4200 cal yr bp before returning to 1 m amsl since 4200 cal yr bp sea level has remained within one meter of the present day level and the beach at bogenfels has prograded seaward from the delayed arrival of sand by longshore drift from the orange river a 6200 cal yr bp coastal midden and a 600 cal yr bp midden 1 7 km from the coast indicate sporadic human utilization of the area the results of this study are consistent with previous studies and help to refine the holocene sea level record for southern africa