oxygen and carbon isotope record of east pacific core v19 30 implications for the formation of deep water in the late pleistocene north atlantic abstract a detailed oxygen and carbon isotope record has been obtained from benthic foraminifera in core v19 30 from the carnegie ridge on the south side of the panama basin expressing these records and the oxygen and carbon isotope records previously published for atlantic core m 12392 on a common timescale it is apparent that the oxygen isotope records are very similar but that the carbon isotope records are quite different by obtaining the carbon isotope gradient between the two sites as a function of time we show that the production of north atlantic deep water has varied over a wide range during the late pleistocene and that the pattern of variation is not simply related to the well known oxygen isotope record although the two oxygen isotope records are very similar changes in the interoceanic gradient are detectable and support the hypothesis that in the glacial mode the north atlantic was colder and less oxygenated than it is today shackleton s 1 1977 interpretation whereby the carbon isotope record from the atlantic core reflects changes in the terrestrial biomass is an over simplification however the record from the pacific core v19 30 probably can be explained in these terms since it probably approximates the carbon isotope record of global mean oceanic dissolved co 2

variations in mode of formation and temperature of oceanic deep waters over the past 125 000 years marked changes in the deep water temperature of the different oceanic basins during the past 125 kyr are revealed by a detailed comparison of the oxygen isotopic composition ofbenthicforaminiferafrom sediment cores taken from the norwegian sea and the pacific atlantic and southern oceans the last interglacial deep water temperatures were similar to the modern ones at the 5e 5d transition around 115 kyr bp the deep water temperatures dropped below approximately 0 c in the pacific and southern indian oceans in the atlantic ocean the deep water temperature dropped in 2 successive steps at 115 and 75ky bp the global ocean deep water temperatures were in the 0 to 1 c range for the whole of the last ice age isotope stages 4 2

direct determination of the timing of sea level change during termination ii an outcrop within the last interglacial terrace on barbados contains corals that grew during the penultimate deglaciation or termination ii we used combined 230th and231pa dating to determine that they grew 135 8 0 8 thousand years ago indicating that sea level was 18 3 meters below present sea level at the time this suggests that sea level had risen to within 20 of its peak last interglacial value by 136 thousand years ago in conflict with milankovitch theory predictions orbital forcing may have played a role in the deglaciation as may have isostatic adjustments due to large ice sheets other corals in the same outcrop grew during oxygen isotope 18o substage 6e indicating that sea level was 38 5 meters below present sea level about 168 0 thousand years ago when compared to the 18o signal in the benthic v19 30 v19 28 record at that time the coral data extend to the previous glacial cycle the conclusion that deep water temperatures were colder during glacial periods

u th ages obtained by mass spectrometry in corals from barbados sea level during the past 130 000 years the study of the sea level record during the last glacial cycle has primarily proceeded indirectly by means of oxygen isotope measurements on foraminifera from deep sea sediments1 2 the direct approach of dating sea level indicators stagnated during the past decade mainly because the samples required to complete our knowledge of the past glaciations are below the present day sea level3 7 using the 14c ages of acropora palmata samples collected by drilling offshore the island of barbados fairbanks8 presented the first detailed chronology for the last deglaciation this radiocarbon chronology is limited to the past 30 kyr because of the short half life of 14c 5 730 yr we must therefore rely on other dating methods to obtain information for the whole last glacial cycle during the past four years 230th 234u dating of corals by thermal ionization mass spectrometry has been shown to be significantly more precise and accurate than the classical counting method9 14 we have used this technique to measure u th ages in coral samples from the barbados collection and from subaerially exposed outcrops see also ref 15 here we present results bearing on the sea level record for the past 130 000 years we conclude that the last deglaciation started 3 000 years earlier than previously thought and confirm that there were two surges in melt water8 at about 11 kyr and 14 kyr bp before present

pore fluid constraints on deep ocean temperature and salinity during the last glacial maximum pore water records of 18 o and cl from odp site 1063a on the bermuda rise constrain the change in seawater 18 o and salinity from the last glacial maximum lgm to the holocene to be 0 75 0 05 and 2 5 0 1 respectively coupled with a measured benthic foraminiferal 18 o change this result means that bottom waters were 4 6 0 8 c cooler than the holocene at the lgm and therefore at or near the seawater freezing point coupled 18 o and chlorinity results give an extrapolated mean ocean lgm to holocene change in 18 o of 0 95 0 09 these data also constrain the past southern source deep water salinity to be 35 76 0 04 psu which is within error of the mean deep ocean value for this time

geoid and topography for infinite prandtl number convection in a spherical shell geoid anomalies and surface and lower boundary topographies are calculated for numerically generated thermal convection in an infinite prandtl number boussinesq axisymmetric spherical fluid shell with constant gravity and viscosity calculations were done for heating entirely from below hfb and entirely from within hfw convective solutions were obtained for rayleigh numbers ra up to 20 times the critical ra in the hfb case and 27 times critical in the hfw case bifurcations that occur with varying ra are associated with different convective patterns boundary topography is positive at upwellings and negative at downwellings absolute topography is greater at the poles than at the equator due to poleward compression of the flow field lower boundary topography is greater than at the surface due to radial compression of the flow field the geoid is primarily dominated by the gravitational potential of surface masses due to surface boundary deformations hence the geoid parallels surface undulations in general boundary deformation increases with increasing cell wavelength this property may elucidate whether core mantle boundary cmb topography is due to mantle convection or mantle dregs chemically dense material which are only indirectly of dynamic origin and hence are unlikely to have the same wavelength dependence in its associated topography the ratios of boundary deformation and geoid to td coefficient of thermal expansion t characteristic temperature drop across the fluid shell and d shell thickness maximize with increasing ra at approximately 10 times ra critical and then steadily decrease out to the maximum ra calculated dimensionless geoid and topography in the hfb case are approximately 5 times greater than in the hfw case at the highest rayleigh numbers investigated dimensionless peak to trough amplitudes of geoid and topography are weak functions of ra which lends some justification to estimating the dimensional values of these quantities with earthlike parameters for parameter values characteristic of the earth s mantle the geoid and upper and lower boundary topograpies are approximately 1 km 10 km and 15 km for the hfb case and approximately 200 m 2 km and 3 km for the hfw case respectively the hfw values correlate with geophysical data more closely than the hfb values suggesting a predominance of internal heating in the mantle although this result is qualfied by the low rayleigh numbers and axisymmetry of the model calculations our study emphasizes that dynamically induced topography and geoid are sensitive to the mode of heating in the earth s mantle

influence of the great lakes on the dynamics of the southern laurentide ice sheet numerical experiments a time dependent flow line ice sheet model is used to explore interactions between last glacial climate the laurentide ice sheet and the great lakes we seek to understand perturbations in the ice flow field that caused three neighboring lobes to leave different geomorphic and sedimentary records driven by reconstructed air temperature variations from 65 to 18 ka the simulated lobe dynamics are consistent with constraints from loess and till chronologies till stratigraphy and ice surface profiles contrasts in lobe dynamics are best explained by the geometry of lakes along each flow line as ice entered these lakes calving influenced glacier mass balance in particular deep water in lake superior likely delayed ice advance into northern wisconsin by promoting large calving losses whereas lobes to the east that encountered shallower water were less affected by calving the driftless area of wisconsin may thus owe its existence at least in part to the presence of lake superior our results suggest that morainal bank evolution should be treated in ice sheet models in lacustrine and shallow marine settings determining the sediment flux to the morainal bank remains a difficult task for example ice advance across central lake superior was probably sediment flux limited otherwise the driftless area would have been glaciated

sea level records at 80 ka from tectonically stable platforms florida and bermuda studies from tectonically active coasts on new guinea and barbados have suggested that sea level at 80 ka was significantly lower than present whereas data from the atlantic and pacific coasts of north america indicate an 80 ka sea level close to that of the present we determined ages of corals from a shallow submerged reef off the florida keys and an emergent marine deposit on bermuda both localities are on tectonically stable platforms distant from plate boundaries uranium series ages show that corals at both localities grew during the 80 ka sea level highstand and geologic data show that sea level at that time was no lower than 7 9 m below present florida and may have been 1 2 m above present bermuda the ice volume discrepancy of the 80 ka sea level estimates is greater than the volume of the greenland or west antarctic ice sheets comparison of our ages with high latitude insolation values indicates that the sea level stand near the present at 80 ka could have been orbitally forced

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

tims u series dating and stable isotopes of the last interglacial event in papua new guinea the extensive flight of uplifted reef terraces which occurs along the vitiaz strait on the northern flank of the huon peninsula in png papua new guinea contains a particularly good record of sea level changes in the last 250 ky the huon terraces were the target of an international expedition which took place in july august 1988 in particular we searched for suitable samples for u series dating in a reef complex designated as vii which is correlated with the last interglacial episode and high sea level stand this complex is composed of a barrier reef viib a lagoon and a fringing reef viia twelve corals from these terraces and two corals from the older reef complex viii were selected for analysis the petrography oxygen and carbon isotope compositions and magnesium and strontium concentrations were determined along with the concentrations and isotopic compositions of uranium and thorium 230 th 234 u ages of the corals with 99 aragonite having primary textures and which show u sr ratios around 0 4 10 3 and initial 234 u values close to that of present seawater appear to be reliable the most reliable ages from complex vii corals fall in two tight groups centered at 118 ky and 134 ky corals with 234 u t values higher than 160 and u sr ratios substantially lower than seawater are assumed to have undergone diagenetic alteration which appears to be common in this area the simplest model for sea level height for terrace vii is a continuous rise between 134 and 118 ky alternatively there may have been two periods of rapid sea level rise in contrast in the bahamas there is evidence that sea level remained rather constant over the time interval 132 to 120 ky the absence of ages between 132 and 120 ky in png could be the result of changes in the local tectonic uplift rates during that time or erosion that disrupted the continuous record in any event we find no basis for accepting a single brief time for the age of the last interglacial and applying this age as a precise chronometer for worldwide correlation or as a test of climatic models the older ages reported here precede the milankovitch solar insolation peak at 128 ky and the younger ages are 10 ky after this peak if the present high precision data are correct then it will be necessary to reassess the validity of the milankovitch theory of climatic changes the fundamental issue which must now be resolved is a means of identifying coral samples that have not been disturbed by diagenetic processes

synchronous high frequency oscillations in tropical sea surface temperatures and north atlantic deep water production during the last glacial cycle stable isotopic measurements of g sacculifer and c wuellerstorfi in a core from the western equatorial atlantic imply that there are parallel suborbital oscillations in surface water hydrography and deep water circulation occurring during oxygen isotope stages 2 and 3 low values of g sacculifer 18o accompany high values of c wuellerstorfi 13c linking warmer sea surface temperatures ssts in the tropics with increased production of lower north atlantic deep water nadw the amplitude of the 18o oscillations is 0 6 or 2 3 c which is superimposed on a glacial interglacial amplitude of about 2 1 using the g sacculifer 18o data we calculate that surface waters were colder during stage 2 than calculated by climap 1976 1981 the longer period 2 kyr oscillations in air temperature recorded in the greenland and antarctic ice cores appear to correlate with oscillations in sea surface temperature in the equatorial atlantic the magnitude of these oscillations in tropical sst is too large to have resulted from changes in meridional heat transport caused by the global conveyor alone the apparent synchroneity of equatorial sst and polar air temperature changes as well as the amplitude of the sst changes at the equator are consistent with the climate effects expected from changes in the atmosphere s greenhouse gas content h2ovapor co2 and ch4

oxygen isotopes and sea level from the time that detailed oxygen isotope records derived from foraminifera living in the constant temperature environment of the abyssal ocean became available there has been a discrepancy between the ice volume record that these records imply and that derived from the altitude of dated coral terraces around the world here we re examine the data and conclude that the temperature of the abyssal ocean has been an actively varying component of the climate system

ice age paleotopography a gravitationally self consistent theory of postglacial relative sea level change is used to infer the variation of surface ice and water cover since the last glacial maximum lgm the results show that lgm ice volume was approximately 35 percent lower than suggested by the climap reconstruction and the maximum heights of the main laurentian and fennoscandian ice complexes are inferred to have been commensurately lower with respect to sea level use of these ice age boundary conditions in atmospheric general circulation models will yield climates that differ significantly from those previously inferred on the basis of the climap data set

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

drowned coralline algal dominated deposits off lanai hawaii carbonate accretion and vertical tectonics over the last 30 ka we present detailed bathymetry remotely operated vehicle rov and submersible observations and sedimentary and radiocarbon age data from carbonate deposits recovered from two submerged terraces at 150 m t1 and 230 m t2 off lanai hawaii the tops of the terraces are veneered by relatively thin b5 m in situ accumulations of coralline algal nodule coralgal nodule halimeda and a derived oolitic facies deposited in intermediate 30 60 m to deep fore reef slope settings 60 120 m the data are used to develop a sedimentary facies model that is consistent with eustatic sea level variations over the last 30 ka both nodule facies on t1 and t2 initiated growth 30 29 ka following a fall in sea level of 50 m and increase in bottom currents during the transition from marine isotope stage 3 to 2 the nodules accreted slowly throughout the last glacial maximum when sea level was relatively stable drowning occurred during the early deglaciation 17 16 ka and was marked by the complete drowning of coralline algal nodules facies on t2 and incipient drowning of coralgal facies on t1 abrupt sea level rise during the middle deglaciation perhaps associated with global meltwater pulse 1a 14 15 ka finally drowned the coralgal facies on t1 which in turn was overlain by a deep water halimeda facies or an oolitic facies derived from upslope our data indicates that lanai has experienced relatively little vertical tectonic movement over the last 30 ka using paleobathymetric data derived from the sedimentary facies age vs depth relationships and published sea level curves we estimate that lanai could be either slowly uplifting or subsiding but at rates b0 1 m kyr uplift or b0 4 m kyr subsidence over this 30 kyr period d 2005 elsevier b v all rights reserved

subglacial drainage eskers and deforming beds beneath the laurentide and eurasian ice sheets glaciological theory predicts that the subglacial drainage network at the base of gently sloping ice sheets resting on deforming sediment should consist of many wide shallow probably braided canals distributed along the ice sediment interface rather than an arborescent network of relatively few large tunnels as would develop over a rigid substrate a corollary prediction examined here is that eskers which form in large subglacial tunnels should be rare where subglacial bed deformation occurred but they may be relatively common where the bed was rigid bed deformation would be most likely where subglacial till was relatively continuous fine grained and of low permeability that is in regions where till is derived primarily from underlying sedimentary bedrock but unlikely where discontinuous coarse grained high permeability till was derived from underlying crystalline bedrock the observed distribution of eskers in areas covered by the laurentide and eurasian british scandinavian and barents sea ice sheets during the last glaciation shows that most eskers occur over crystalline bedrock overlain by discontinuous high permeability till but are rare or absent over sedimentary bedrock overlain by fine grained low permeability till thus matching reasonably well our prediction glaciological theory and geologic evidence indicate that esker systems on a subcontinental scale are time transgressive sedimentological evidence for a canal drainage system appears to be present in fine grained tills where eskers are largely absent

quaternary deep sea temperature histories derived from benthic foraminiferal mg ca abstract we have generated benthic foraminiferal mg ca records from eastern tropical atlantic core m16772 3 9 km and eastern tropical pacific core tr163 31p 3 2 km to assess the potential for using benthic mg paleothermometry to reconstruct quaternary bottom water temperature histories variations in mg ca records from both the atlantic and pacific show a significant correlation with climatic oscillations of the last 330 kyr shell mg ca peaks during interglacial episodes with marine isotope stage mis 5e mg ca nearly matching holocene values in both cores lower mg ca values occur during glacial intervals to estimate temperatures from downcore mg ca we have augmented the published cibicidoides sp mg ca temperature dataset rosenthal et al geochim cosmochim acta 61 1997 3633 3643 with new data to include the temperature range of deep waters applying the 10 9 change in mg ca per c defined by the expanded calibration to the deep atlantic data implies glacial interglacial shifts in deep water temperature of 2 4 c over the last 300 kyr temperature estimates are comparable to deep atlantic temperature changes proposed by labeyrie et al nature 327 1987 477 482 there is greater uncertainty in deriving temperatures from the tropical pacific core due to a limited uvigerina spp core top calibration set however glacial interglacial temperature oscillations appear to be on the order of 2 3 c in addition core tr163 31p records clear millennial scale mg ca and 18 o oscillations in mis 3 corresponding to temperature fluctuations of 0 5 c additional calibration studies are needed to address potential secondary effects on mg ca

north atlantic deepwater temperature change during late pliocene and late quaternary climatic cycles variations in the ratio of magnesium to calcium mg ca in fossil ostracodes from deep sea drilling project site 607 in the deep north atlantic show that the change in bottom water temperature during late pliocene 41 000 year obliquity cycles averaged 1 5 c between 3 2 and 2 8 million years ago ma and increased to 2 3 c between 2 8 and 2 3 ma coincidentally with the intensification of northern hemisphere glaciation during the last two 100 000 year glacial to interglacial climatic cycles of the quaternary bottom water temperatures changed by 4 5 c these results show that glacial deepwater cooling has intensified since 3 2 ma most likely as the result of progressively diminished deepwater production in the north atlantic and of the greater influence of antarctic bottom water in the north atlantic during glacial periods the ostracode mg ca data also allow the direct determination of the temperature component of the benthic foraminiferal oxygen isotope record from site 607 as well as derivation of a hypothetical sea level curve for the late pliocene and late quaternary the effects of dissolution on the mg ca ratios of ostracode shells appear to have been minimal

high precision u series dating of corals from western australia and implications for the timing and duration of the last interglacial abstract u series ages using methods of thermal ionisation mass spectrometry tims are reported for last interglacial fossil reefs along the stable coastal margin of western australia thorium isotope ratios were measured with superior precision using methods of charge collection high levels of precision in the measurement of both uranium and thorium isotopes has reduced the age uncertainty due to analytical errors excluding the uncertainty in the decay constants by a factor of four over the precisions reported by many earlier tims workers uncertainties in 234u t determined from both 230th 238u and 234u 238u are also significantly smaller than previously reported allowing samples which have undergone diagenetic exchange of uranium and thorium to be more easily identified strict criteria were adopted to screen the new western australian data reliable ages range from 127 to 122 ka published tims observations from other localities have been assessed using the same strict criteria when these are combined with glacio hydro isostatic sea level models they indicate that the last interglacial period occurred from at least 130 to 117 ka however these age constraints are largely determined from single data points and need to be verified with additional ages before considering them to be robust estimates for the timing of onset and termination of the last interglacial globally the main episode of reef growth appears to be confined to a narrow interval occurring from 127 to 122 ka in direct agreement with the narrow range in ages obtained from the western australian sites this may indicate that the last interglacial was of short duration extending from 127 to 122 ka only alternatively this interval may reflect a major reef building event in the middle of a longer duration 130 117 ka interglacial interval

provenance sea level and monsoon climate controls on silicate weathering of yellow river sediment in the northern okinawa trough during late last glaciation abstract high resolution multi proxy records including geochemical and grain size data from detrital sediments of iodp site u1429 in the northern okinawa trough provide reliable evidence for constraining sediment source and transport processes they also allow silicate weathering and erosion controlled by sea level change and east asian summer monsoon evolution since 34 ka to be reconstructed provenance proxies indicated that sediments in the northern okinawa trough were mainly supplied by the yellow river middle reach at 34 8 ka the low sea level and proximity of paleo yellow river mouth to the northern okinawa trough were the causes of the dominant yellow river input after 8 ka a retreated yellow river mouth coupled with the blocking effect of the kuroshio current and its branches together with strong east asian summer monsoon precipitation resulted in relatively strong sediment input from kyushu to the northern okinawa trough meanwhile yellow river upper reach supplied more sediments to the study site than that during the 34 8 ka on glacial interglacial scale silicate weathering proxies indicate that the core sediment was more weathered during the last glacial and deglacial than that in the modern yellow river we attribute this to the increased upper reach sediment input which supplied more weak weathered sediment to the study site during the holocene besides composite effect of weathering during glacial and deglacial sediment production and additional weathering upon subaerial exposure of shelf deposits during low sea level stage as well as older weathered sediments reworking during sea level rise could also account for this weathering regime on multi millennial scale from 34 to 18 5 ka silicate weathering was mainly controlled by the east asian summer monsoon with a cooling and drying climate associated with weakened summer monsoon activity this is consistent with the reduced alteration of sediments eroded from the yellow river basin from 18 5 to 8 ka strong reworking of older weathered sediments overwhelmed the east asian summer monsoon in controlling silicate weathering which induced a continuous increase in chemical alteration of the sediments during this period

coupled climate and sea level changes deduced from huon peninsula coral terraces of the last ice age abstract huon peninsula papua new guinea is a tectonically unstable uplifting shoreline ringed by emergent coral terraces the terraces were formed during episodes of rapid sea level rise when corals constructed large discrete coral platforms that were subsequently uplifted uranium series ages of four prominent huon peninsula last glacial ois 3 coral terraces coincide with the timing of major north atlantic climate reversals at intervals of 6000 7000 yr between 30 000 yr and 60 000 yr ago terrace elevations when combined with uplift indicate 10 15 m high sea level excursions at these times we attribute the growth of the terraces directly to sea level rises arising from ice calving episodes from major north atlantic ice sheets and the antarctic ice sheet that precipitated extremes of cold climate called heinrich events these periods are associated with major discharges of land based ice and enhanced concentrations of ice rafted debris in deep sea cores sea levels at this time were 60 90 m lower than present

submerged late pleistocene reefs on the tectonically stable s e florida margin high precision geochronology stratigraphy resolution of substage 5a sea level elevation and orbital forcing abstract a well preserved submerged in situ fossil reef tract lies offshore of the southeast florida carbonate margin in the florida keys cores in two transects enabled reconstruction of reef stratigraphy and paleoenvironments paleo water depths and paleo sea levels because florida is tectonically stable the elevation data required correction only for the known minor subsidence rate twenty eight pristine aragonitic corals were dated via high precision tims u series methods to produce a comprehensive late pleistocene and early holocene geochronology the pleistocene section of the fossil reef includes a thick section of substage 5a reef growth recorded from 15 to 11 m msl spanning an age range of 86 2 80 9 ka paleoenvironmental reconstruction local water quality constraints and elevations of concurrent bahamian speleothem growth combine to limit sea level to 9 0 m msl at 83 ka this coincides unlagged with the 82 ka 65 n july insolation peak the absence of any lag suggests that the earlier peak in obliquity at 92 ka also controls paleoclimate and sea level a below present sea level estimate for substage 5a from the florida fossil reef data coincides more closely with uplift corrected reef data estimates of 15 to 13 m msl from tectonic margins such as barbados and haiti than with higher than present sea levels derived from detrital corals from bermuda and the u s atlantic coastal plain the best tims dates on corals and speleothem constraining sea level combine to produce a new regional sea level curve for the atlantic caribbean region for late isotope stage 5 and early stage 4

holocene growth history of a reef complex on a cool water carbonate margin easter group of the houtman abrolhos eastern indian ocean the houtman abrolhos reefs situated on the western continental margin of australia occupy a transitional position between cool water shelf carbonate sediments to the south and more tropical environments to the north their existence at the outer limits of the geographical range for coral reef growth is a result of the warm poleward flowing leeuwin current though the modern reefs differ ecologically from tropical reefs their geological characteristics have been little known until recently each of the three island groups in the abrolhos consists of a central platform of last interglacial reefs about which windward and leeward holocene reefs have developed asymmetrically in the easter group the subtidal windward reef in the west is ca 10 m thick and is backed by a leeward prograding lagoon sand sheet which is 0 3 m thick the emergent parts of the leeward reefs in the east consist of an upward shallowing sequence comprising reef facies peritidal rudstone facies and coral rubble storm ridges this is underlain by over 26 m of holocene reef facies coring and dating of the holocene reefs using both u th tims and 14 c methods in the easter group has shown significantly different lithofacies in the windward and leeward reefs and has allowed reconstruction of holocene reef growth and sea level history coralline algal bindstones and interbedded coral framestone facies characterise the relatively slow growing windward holocene reefs whereas the fast growing leeward reefs consist of coral framestone facies which are dominated by acropora the leeward reefs commenced growth about 10 000 u th years ago and the morley reef grew to 0 3 m above present sea level by 6400 u th years b p recording a relative high sea level event this generated holocene constructional topography characterised by blue hole terrain windward holocene reef growth commenced after 8200 u th years b p following erosion of the windward part of the last interglacial platform high wave energy and competition with macroalgae limited coral growth and the coralline algal dominated windward reefs grew more slowly to sea level the holocene sea level record provided by dates from the 26 m core of the morley reef a keep up reef is the first such record from the western continental margin of australia

protactinium 231 dating of carbonates by thermal ionization mass spectrometry implications for quaternary climate change measurement of protactinium 231 231pa in carbonates by thermal ionization mass spectroscopy yields 231pa ages that are more than 10 times more precise than those determined by decay counting carbonates between 10 and 250 000 years old can now be dated with 231pa methods barbados corals that have identical 231pa and thorium 230 230th ages indicate that the timing of sea level change over parts of the last glacial cycle is consistent with the predictions of the astronomical theory two devils hole calcite subsamples record identical 231pa and 230th ages suggesting that the chronology of this climate record is accurate

mis 5a and mis 3 relatively high sea level stands on the hatay samandag coast eastern mediterranean turkey abstract the coastal belt of hatay samandag in the east mediterranean is marked by the intersection of the african arabian and eurasian anatolian platelet plates where several quaternary shorelines related to relative sea level changes can be seen above the current sea level in this study the most common and best preserved high sea level markers of the marine isotope stage mis 5 and mis 3 shorelines were dated for the first time using the mollusc based electron spin resonance esr method as a result of this research the age of the late mis 5 and mis 3 sea level highstands in the eastern mediterranean the elevation of the corresponding shoreline at samandag coast and the vertical component of the late quaternary tectonic movements which has an impact on shoreline were determined the shorelines at 48 43 m elevations between cevlik and samandag at 58 6 m in tekebasi and at 21 m at keldag have been dated to approximately 72 ka and therefore are correlated with mis 5a the shoreline at 40 39 m elevations between cevlik and samandag has been dated to approximately 53 ka and therefore is correlated with mis 3 according to the position of the mis 5a shorelines the uplift rate over the last 72 ka was 0 88 mm y between cevlik and samandag 1 08 mm y in tekebasi and 0 56 mm y in keldag yielding a 0 84 mm y average this rather fast uplift appears to be related to the vertical component of the strike slip active faults in the samandag antakya fault zone

pore fluid constraints on the temperature and oxygen isotopic composition of the glacial ocean pore fluids from the upper 60 meters of sediment 3000 meters below the surface of the tropical atlantic indicate that the oxygen isotopic composition 18 o of seawater at this site during the last glacial maximum was 0 8 0 1 per mil higher than it is today combined with the 18 o change in benthic foraminifera from this region the elevated ratio indicates that the temperature of deep water in the tropical atlantic ocean was 4 c colder during the last glacial maximum extrapolation from this site to a global average suggests that the ice volume contribution to the change in 18 o of foraminifera is 1 0 per mil which partially reconciles the foraminiferal oxygen isotope record of tropical sea surface temperatures with estimates from barbados corals and terrestrial climate proxies

precise chronology of the last interglacial period 234u 230th data from fossil coral reefs in the bahamas a detailed study of 238 u 234 u 230 th ages was made for different coral species from two bahamian reefs to determine the time scale of the sea level high during the last interglacial period using recently developed mass spectrometric techniques for the measurement of u and th isotopes thirty seven coral samples were analyzed in replicate typical errors at 125 ky are 1 5 ky 2 and 3 ky time intervals appear to be well resolved this high precision permits detailed chronologic study with time resolution adequate to define stages of the reef s history these data demonstrate that the time between transgression and regression of the ocean in the last interglacial was about 12 ky after which sea level fell rapidly at more than 2 m ky the high sea level stand began possibly by 132 ky and certainly by 129 ky ago when sea level reached 6 m above present mean low sea level high sea level was sustained until 120 ky and then fell rapidly this time period covers the milankovitch insolation peak at 65 n but is not sharply defined and the sea level high lasted from about 4 ky before the insolation peak to 8 ky after it we find no evidence for a double peak of sea level rise in the last interglacial episode that is high stands at both 125 and 142 ky there appears to be some discrepancy between this precise chronology for a coral reef on a tectonically stable platform and the chronology assigned to deep sea sediments the present results show that the duration of the last interglacial led to a 12 ky period of high sea level stand which is much longer than the insolation peak the study area consists of two sizeable bank barrier coral reefs of sangamon age that crop out along the coast northwest of cockburn town on san salvador island and at devil s point on great inagua island the initial stage of reef development is not revealed at either site but the main parts of both reefs are well preserved at cockburn town the beginning of the reef was marked by colonization of acropora palmata on hardground areas and possibly other corals at 132 ky ago patch reefs at the southeastern flank of the developing reef were growing by 129 to 126 ky ago by 126 to 123 ky ago the crest of the reef was formed by the frame building coral a palmata and associated patch reefs flourished along its flanks a palmata coral heads grew upward to a mean low sea level 6 m above the present one the reef began to decline as sea level dropped at about 123 to 120 ky ago near two measured profiles at devil s point the top of a rubblestone dominated by a cervicornis and patch reef corals preserved in growth position have been beveled off and represent an ancient wave cut surface 230 th ages on corals below and above this surface indicate that it was cut at about 125 1 ky ago

controls on architecture of the late cretaceous to cenozoic southern middle magdalena valley basin colombia the maastrichtian cenozoic southern middle magdalena valley basin of colombia contains a unique record of unconformities strata and structure from which we extract the histories of exhumation of the central cordillera to the west and evolution of the eastern cordillera fold and thrust belt to the east this study integrates field based analyses of stratigraphy laboratory analyses of provenance fission track thermochronology vitrinite reflectance data volcanic ash geochronology and studies of synorogenic geometries and structure displayed in seismic data a major unconformity the middle magdalena valley unconformity formed by eastward migration of central cordillera uplift during late cretaceous to early eocene time which transformed a maastrichtian marine basin into a paleocene depositional piedmont area this transformation is recorded by a coarsening upward sequence of marine shales to alluvial fan conglomerates which was partly eroded during further early eocene propagation of central cordillera deformation cessation of this phase of uplift led to formation of a pediment surface the middle magdalena valley unconformity which was buried by westward onlapping middle eocene to neogene alluvial deposits middle eocene to neogene facies paleoflow and unconformities were controlled by eastern cordillera deformation in the eastern cordillera foot hills growth strata and thermal history reveal two phases of folding of middle eocene oligocene and late miocene ages prior to intense pliocene pleistocene uplift two unconformities of early late miocene and pliocene pleistocene ages occur to the west of the eastern cordillera and record flexural tilting related to episodes of eastern cordillera loading

orbital forcing of the marine isotope stage 9 interglacial milankovitch orbital forcing theory has been used to assign time scales to many paleoclimate records however the validity of this theory remains uncertain and independent sea level chronologies used to test its applicability have been restricted largely to the past approximately 135 000 years here we report u series ages for coral reefs formed on henderson island during sea level high stands occurring at approximately 630 000 and approximately 330 000 years ago these data are consistent with the hypothesis that interglacial climates are forced by northern hemisphere summer solar insolation centered at 65 degrees n latitude as predicted by milankovitch theory

uranium thorium protactinium dating systematics abstract with precise 234u 230th and 231pa data available 230th and 231pa ages can now be tested rigorously for concordancy if the material is not concordant the isotopic characteristics of this material may be examined in some detail here models similar to those used to describe the u pb system are evaluated for use in u th pa studies for the case in which initial 230th and 231pa concentrations are effectively zero the systematics of concordia plots in relation to models of variation in 234u episodic u loss or gain continuous u loss or gain and continuous 234u 230th and 231pa gain or loss are considered for the case in which initial u concentration is significant for example in many carbonate deposits we also examine linear u uptake models for the case in which initial u concentration is effectively zero for example in teeth and bones such models should prove useful in interpreting data from materials that have behaved as open systems in particular these models may help constrain the nature of diagenetic processes and in some situations it may be possible to determine or constrain true ages with materials that have behaved as open systems

precise timing of the last interglacial period from mass spectrometric determination of thorium 230 in corals the development of mass spectrometric techniques for determination of 230 th abundance has made it possible to reduce analytical errors in 238 u 234 u 230 th dating of corals even with very small samples samples of 6 x 10 8 atoms of 230 th can be measured to an accuracy of 3 percent 2 and 3 x 10 10 atoms of 230 th can be measured to an accuracy of 0 2 percent the time range over which useful age data on corals can be obtained now ranges from about 50 to about 500 000 years for young corals this approach may be preferable to 14 c dating the precision with which the age of a coral can now be determined should make it possible to critically test the milankovitch hypothesis concerning pleistocene climate fluctuations analyses of a number of corals that grew during the last interglacial period yield ages of 122 000 to 130 000 years the ages coincide with or slightly postdate the summer solar insolation high at 65 n latitude which occurred 128 000 years ago this supports the idea that changes in pleistocene climate can be the result of variations in the distribution of solar insolation caused by changes in the geometry of the earth s orbit and rotation axis

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

climate impact of late quaternary equatorial pacific sea surface temperature variations magnesium calcium data from planktonic foraminifera in equatorial pacific sediment cores demonstrate that tropical pacific sea surface temperatures ssts were 2 8 0 7 c colder than the present at the last glacial maximum glacial interglacial temperature differences as great as 5 c are observed over the last 450 thousand years changes in sst coincide with changes in antarctic air temperature and precede changes in continental ice volume by about 3 thousand years suggesting that tropical cooling played a major role in driving ice age climate comparison of sst estimates from eastern and western sites indicates that the equatorial pacific zonal sst gradient was similar or somewhat larger during glacial episodes extraction of a salinity proxy from the magnesium calcium and oxygen isotope data indicates that transport of water vapor into the western pacific was enhanced during glacial episodes

timing and duration of the last interglacial evidence for a restricted interval of widespread coral reef growth abstract we report new mass spectrometric u series ages for eight last interglacial fossil reefs along the continental margin of western australia corals were selected in growth position from localities that are characterized by apparently low levels of diagenesis and relative tectonic stability so that the fossil reefs provide critical information on last interglacial sea levels without requiring corrections for tectonic movements in addition we have improved the constraint on the timing of onset of reef growth by recovering drill core coral from the base of the reefs uranium and thorium isotopes were measured with high levels of precision leading to improvements in age resolution and allowing samples which have undergone diagenetic exchange of uranium and thorium to be more easily identified and discarded these data supplement our previous results for rottnest island and leander point leading to more than seventy mass spectrometric u series ages from which constraints can be placed on the timing duration and character of the last interglacial sea level highstand reliable ages show that reef growth started contemporaneously at 128 1 ka along the entire western australian coastline while relative sea levels were at least 3 m above the present level because western australia is located far from the former penultimate glacial maximum ice sheets and are not significantly effected by glacial unloading these data constrain the timing of onset of the last interglacial period to 128 1 ka assuming reef growth started soon after sea level approached interglacial levels a unique regressive reef sequence at mangrove bay constrains the timing of termination of the last interglacial period to 116 1 ka the major episode of reef building however both globally and locally along the western australian coast is restricted to a very narrow interval occurring from 128 ka and 121 ka suggesting that global ocean surface temperatures were warm and or sea levels were stable enough to allow prolific reef growth only during the earlier part of the last interglacial

a radiometric calibration of the specmap timescale the astronomical theory of climate change asserts that earth s climate is affected by changes in its orbit which vary the seasonal and latitudinal distribution of solar radiation this theory is the basis of the orbitally tuned specmap timescale a key constraint for this important chronology was the mid point of the penultimate deglaciation initially dated to 127 000 years ago recent work suggests this event may be considerably older casting doubt on the astronomical theory the specmap timescale and the accuracy of orbitally tuned chronologies difficulties with u th coral dating of sea level events have impeded progress on this problem because most corals are not closed systems here we use a new approach to u th dating that corrects for open system behavior and produces a sea level curve of sufficient resolution to confidently correlate with specmap over the last 240 000 years permitting a reassessment of both this critical chronology and a central tenet of climate change theory high precision ages for 24 oxygen isotope events provide a 240 000 year chronology for marine 18o records that is independent of orbital tuning assumptions although there appear to be significant differences between the radiometric and orbitally tuned timescales near the lastglacial maximum and at the marine isotope stage 7 6 boundary a comparison of radiometric and specmap ages for identical isotope events suggest that the specmap timescale is quite accurate and that its errors were in general overestimated despite suborbital complexity orbital cyclicity is clearly evident in our record high amplitude sea level oscillations at periods greater than 20 000 years are very close in phase to summer insolation in the northern hemisphere although sea level changes cannot be uniquely tied to a specific season or latitude of insolation forcing the simplest explanation is that long period high amplitude sea level change is linked to northern hemisphere insolation forcing these results validate the principles of orbital tuning and suggest such timescales are generally robust

rock varnish microlamination dating of late quaternary geomorphic features in the drylands of western usa abstract varnish microlamination vml dating is a correlative age determination technique that can be used to date and correlate various geomorphic features in deserts in this study we establish a generalized late quaternary i e 0 300 ka varnish layering sequence for the drylands of western usa and tentatively correlate it with the specmap oxygen isotope record we then use this climatically correlated varnish layering sequence as a correlative dating tool to determine surface exposure ages for late quaternary geomorphic features in the study region vml dating of alluvial fan deposits in death valley of eastern california indicates that during the mid to late pleistocene 5 15 ky long aggradation events occurred during either wet or dry climatic periods and that major climate shifts between glacial and interglacial conditions may be the pacemaker for alteration of major episodes of fan aggradation during the holocene interglacial time however 0 5 1 ky long brief episodes of fan deposition may be linked to short periods of relatively wet climate vml dating of alluvial desert pavements in death valley and the mojave desert reveals that pavements can be developed rapidly

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

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

rapid fluctuations in sea level recorded at huon peninsula during the penultimate deglaciation about 140 000 years ago the breakup of large continental ice sheets initiated the last interglacial period sea level rose and peaked around 135 000 years ago about 14 meters below present levels a record of last interglacial sea levels between 116 000 years to 136 000 years ago is preserved at reef vii of the uplifted coral terraces of huon peninsula in papua new guinea however corals from a cave situated about 90 meters below the crest of reef vii are 130 000 2000 years old and appear to have grown in conditions that were 6 c cooler than those at present these observations imply a drop in sea level of 60 to 80 meters after 130 000 years sea level began rising again in response to the major insolation maximum at 126 000 to 128 000 years ago the early about 140 000 years ago start of the penultimate deglaciation well before the peak in insolation is consistent with the devils hole chronology

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

the timing of high sea levels over the past 200 000 years the 230 th ages and 234 u 238 u ratios were determined for barbados corals that grew during periods of high sea level within the last 200 000 years the similarity of the initial 234 u 238 u ratios of some of the corals to the modern marine value suggests that these samples are pristine and that the marine 234 u 238 u ratio 83 000 and 200 000 years ago was within 2 per mil of the modern value the accuracies of the 230 th ages are evaluated on the basis of the 234 u 238 u values and a model of the behavior of uranium and thorium isotopes during diagenesis for the last three interglacial and two intervening interstadial periods sea level peaked at or after peaks in summer insolation in the northern hemisphere this overall pattern supports the idea that glacial interglacial cycles are caused by changes in earth9s orbital geometry the sea level drop at the end of the penultimate interglacial the last interglacial and a subsequent interstadial period lagged behind the decrease in insolation by 5 000 to 10 000 years

pleistocene sea level fluctuations and human evolution on the southern coastal plain of south africa abstract humans evolved in africa but where and how remain unclear here it is proposed that the southern coastal plain scp of south africa may have served as a geographical point of origin through periodic expansion and contraction isolation in response to glacial interglacial changes in sea level and climate during pleistocene interglacial highstands when sea level was above 75 m human populations were isolated for periods of 360 3400 25 yr generations on the scp by the rugged mountains of the cape fold belt climate and vegetation barriers the scp expands five fold as sea level falls from 75 to 120 m during glacial maxima to form a continuous unobstructed coastal plain accessible to the interior an expanded and wet glacial scp may have served as a refuge to humans and large migratory herds and resulted in the mixing of previously isolated groups the expansive glacial scp habitat abruptly contracts by as much as one third in 300 yr during the rapid rise in sea level associated with glacial terminations rapid flooding may have increased population density and competition on the scp to select for humans who expanded their diet to include marine resources or hunted large animals successful adaptations developed on an isolated scp are predicted to widely disperse during glacial terminations when the scp rapidly contracts or during the initial opening of the scp in the transition to glacial maxima the hypothesis that periodic expansion and contraction of the scp as well as the coastal plain of north africa contributed to the stepwise origin of our species over the last 800 thousand years kyr is evaluated by comparing the archeological dna and sea level records these records generally support the hypothesis but more complete and well dated records are required to resolve the extent to which sea level fluctuations influenced the complex history of human evolution

quaternary hinterland evolution of the active banda arc surface uplift and neotectonic deformation recorded by coral terraces at kisar indonesia abstract coral terrace surveys and u series ages of coral yield a surface uplift rate of 0 5 m ka for kisar island which is an emergent island in the hinterland of the active banda arc continent collision based on this rate kisar first emerged from the ocean as recently as 450 ka these uplifted terraces are gently warped in a pattern of east west striking folds these folds are strike parallel to more developed thrust related folds of similar wavelength imaged by a seismic reflection profile just offshore this deformation shows that the emergence of kisar is influenced by forearc closure along the south dipping kisar thrust however the pinnacle shape of kisar and the protrusion of its metamorphic rocks through the forearc basin sediments also suggest a component of extrusion along shear zones or active doming coral encrusts the island coast in many locations over 100 m above sea level terrace morphology and coral ages are best explained by recognizing major surfaces as mostly growth terraces and minor terraces as mostly erosional into older terraces all reliable and referable coral u series ages determined by mc icp ms correlate with marine isotope stage mis 5e 118 128 ka the only unaltered coral samples are found below 6 m elevation however an unaltered tridacna giant clam shell in growth position at 95 m elevation yields a u series age of 195 31 ka which corresponds to mis 7 this age agrees with the best fit uplift model for the island loose deposits of unaltered coral fragments found at elevations between 8 and 20 m yield u series ages of

sea level changes forced ice breakouts in the last glacial cycle new results from coral terraces abstract sea level cycles recorded by coral terraces at huon peninsula hp in papua new guinea match rapid climate changes that occurred between 30 000 and 65 000 years ago seen in greenland ice cores and marine sediments each cycle of 6000 7000 years ended with a sea level rise of 10 15 m lasting 1000 2000 years following a longer period of falling sea level precise dating shows that each rise corresponds to a heinrich episode of ice rafted detritus in north atlantic signalling massive ice outbreak from north america sea level may be the trigger that forced near synchronous breakouts of ice from north america and eastern greenland the hp sea level changes also correspond to similar cycles in benthic oxygen isotopes reported from the north atlantic which are too large to be explained entirely in terms of ice volumes jointly the sea level and isotope records suggest that the north atlantic deep ocean cooled as sea level fell and warmed as sea level rose in each 6000 year cycle

rapid sea level fall and deep ocean temperature change since the last interglacial period we have dated huon peninsula papua new guinea and barbados corals that formed at times since the last interglacial period applying both 230 th and 231 pa dating techniques as a test of age accuracy we show that marine isotope stage mis 5e ended prior to 113 1 8 0 7 kyr when sea level was 319 m during mis 5b sea level was 357 m at 92 6 8 0 5 kyr having dropped about 40 m in approximately 10 kyr during the mis 5c 5b transition sea level then rose more than 40 m during the mis 5b 5a transition also in about 10 kyr mis 5a lasted until at least 76 2 8 0 4 kyr at a level of 324 m at that time combined with earlier data that places mis 4 sea level at 381 m at 70 8 kyr our late mis 5a data indicate that sea level fell almost 60 m in less than 6 kyr 10 6 m kyr during the mis 5 4 transition the magnitude of the drop is half that of the glacial interglacial amplitude and approximatelyequivalent to the volume of the present dayantarctic ice sheet during this interval the minimum average rate of net continental ice accumulation was 18 cm yr likely facilitated by efficient moisture transport from lower latitudes at three specific times 60 6 8 0 3 50 8 8 0 3 and 36 8 0 2 kyr during mis 3 sea level was between 385 and 374 m sea level then dropped to 3107 m at 23 7 8 0 1 kyr early in mis 2 before dropping further to last glacial maximum lgm values and then rising to present values during the last deglaciation times of rapid sea level drop correspond to times of high winter insolation at low northern latitudes and high winter latitudinal gradients in northern hemisphere insolation supporting the idea that these factors mayhave resulted in high water vapor pressure in moisture sources and efficient moisture transport to high latitude glaciers therebycontributing to glacial buildup we combined our sea level results with deep sea n 18 o records as a means of estimating the temperature and ice volume components in the marine n 18 o record this analysis confirms large deep ocean temperature shifts following mis 5e and during termination i deep ocean temperatures changed bymuch smaller amounts between mis 5c and 2 maximum temperature shift in the deep pacific is about 2 whereas the shift at a site in the atlantic is 4 under glacial conditions temperatures at both sites are near the freezing point the shift in the atlantic is likelycaused bya combination of changing proportions of northern and southern source waters as well as changing temperature at the sites where these deep waters form

comment on younger dryas sea level and meltwater pulse 1b recorded in barbados reefal crest coral acropora palmata by n a abdul et al based on new u th ages of corals drilled offshore barbados abdul et al 2016 have confirmed the existence of the abrupt stratigraphic feature called meltwater pulse 1b mwp 1b which they interpret as being due to a very large and global sea level step change dated at about 11 3 kyr before present approximately 15 m and equivalent to twice the amount of water stored in the present greenland ice sheet this contrasts with the tahiti record in which mwp 1b is essentially absent or very small as carlson and clark 2012 and lambeck et al 2014 also conclude in their recent reviews of deglacial sea levels at the global scale however the evidence provided by abdul et al and their main conclusions are not convincing as they are affected by the following three main problems which may explain the apparent discrepancies problem 1 barbados is located in a subduction zone which was also active throughout the late glacial period furthermore the barbados cores studied by abdul et al were drilled on both sides of the extension of a tectonic feature identified at the southern tip of barbados south point as underlined by several studies of the barbados stratigraphy problem 2 fossil samples of acropora palmata may not be reliable sea level markers during rapid and large sea level rises indeed the asexual reproduction strategy of this species may not be optimal to keep up when the water depth is increasing very rapidly this may in part explain why the living depth of a palmata at barbados was significantly greater than 5 m during some periods of the last deglaciation notably between 14 5 and 14 kyr b p and possibly between 14 and 11 5 kyr b p problem 3 the slow glacio isostatic adjustment and the rapid responses due to gravitational changes of ice and water masses complicate the interpretation of individual relative sea level rsl records at specific locations therefore the barbados and tahiti record cannot be compared directly in terms of absolute sea level values as done by abdul et al in addition different glaciohydroisostatic adjustments at the two sites may also have contributed to the observed discrepancy between their deglacial rsl records

new precipitation and accumulation maps for greenland annual total precipitation and the annual accumulation on the greenland ice sheet are evaluated and presented in two maps the maps are based on accumulation measurements of 25 1 pits and cores obtained from the upper accumulation zone and precipitation measurements made at 35 meteorological stations in the coastal region to construct the accumulation map the annual precipitation was split into solid and liquid precipitation components annual total precipitation exceeding 2500 mm w e occurs on the southeastern tip of greenland while the minimum precipitation is estimated to occur on the northeastern slope of the ice sheet the mean annual precipitation for all of greenland is 340 mm w e the largest annual accumulation of about 1500 mm w e is found on the glaciers in the southeastern corner of greenland while the smallest accumulation is found on the northeastern slope of the ice sheet west of danmarkshavn the mean accumulation on the greenland ice sheet is estimated at 310 mm w e the regional difference in accumulation is examined with respect to the 850 hpa m bar level circulation the present surface topography is found to play an important role in determining regional accumulation on the ice sheet

late quaternary evolution of coral reefs on a cool water carbonate margin the abrolhos carbonate platforms southwest australia late quaternary coral reefs have developed on the southwestern australian margin which has otherwise been characterised by cool water carbonates since the eocene the houtman abrolhos coral reefs are at the limits of existence extending with the assistance of the leeuwin current a poleward flowing warm water stream into a region dominated by more temperate communities coring in the easter group reefs supported by high precision dating by both view the mathml source tims and 14 c methods has shown vigorous coral growth with reefs over 26 m thick in the holocene and over 15 m thick in the last interglacial each of the three abrolhos platforms consists of a central platform composed of last interglacial reefs about which windward and leeward holocene reefs developed asymmetrically reef peritidal and eolian facies comprise the emergent last interglacial limestones which are extensively calcretized with reef facies up to 5 m above msl the last interglacial high stand lasted for at least 10 ka from 130 to 120 ka and possibly 15 ka from 132 to 117 ka holocene reef facies are also emergent by 0 5 m and are overlain by peritidal and storm ridge facies in an upward shallowing sequence windward 10 m thick and leeward 26 m thick holocene reefs in the easter group show contrasting lithofacies the wave exposed windward reefs consist of a slow growing association of coralline algal bindstones and coral framestones whereas fast growing coral framestones dominate the more protected leeward reefs the leeward reefs commenced growth 10 000 years ago and grew to the present sea level by 6500 years ago generating holocene constructional topography consisting of blue hole terrain in the leeward parts of the platforms

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