history of stage 5 sea level in bermuda review with new evidence of a brief rise to present sea level during substage 5a abstract oxygen isotope substage 5e is represented by the devonshire formation in bermuda the occurrence of these coastal marine deposits to about 5 m indicates pleistocene sea level data in bermuda do not need tectonic corrections a few published u series coral dates suggest that a conglomerate spencer s point formation may have formed during substage 5c geologic mapping however indicates that the eolianite beneath the conglomerate is pre rather than post devonshire formation in age as was previously thought and the aminostratigraphy of marine sheels also confirms the correlation of the spencer s point and devonshire formations substages 5c and 5a are represented by the southampton formation large eolianites comprise the bulk of this formation they are onlapped by a few small younger marine 1 m and eolian deposits aminostratigraphy confirms that these late southampton age deposits are significantly younger than the devonshire formation and u series dates indicate a substage 5a age the setting of some of these deposits along a protected shoreline precludes discounting their position as anomalous due to large storms this evidence that sea level in bermuda was at about present datum late in substage 5a agrees with interpretations of neotyrrhenian deposits of mediterranean shorelines but not with inferences from the deep sea oxygen isotope record or with data from uplifted coral reefs

late pleistocene coastal evolution of san giovanni di sinis west sardinia western mediterranean abstract the upper pleistocene succession of coastal deposits outcropping at san giovanni di sinis west sardinia has been studied since the 1960s however the absence of consistent radiometric ages has allowed the production of competing stratigraphic subdivisions of these deposits with different isotopic stage ois mis attributions the succession is composed of sandy to gravelly shallow marine coastal aeolian and alluvial fan plain deposits facies analysis and log correlations show the presence of three unconformities t1 t2 t3 always overlain by shallow marine deposits cutting through the substrate alluvial fan or aeolian sediments we have collected three samples for optically stimulated luminescence osl dating at the top of each shallow marine deposit the succession is composed of four unconformity bounded units u1 u2 u3 u4 and the new osl dates indicate the presence of three different sea level highstands the first unit u1 which is composed of shallow marine to aeolian deposits and overlies transgressive surface t1 is related to a marine transgression during ois 7 186 13 ky unit 2 is composed of continental deposits and formed during ois 6 unit 3 represents ois 5 and overlies a transgressive surface t2 more precisely subunit u3a is related to ois 5e 120 10 ky eu tyrrhenian or eemian sensu strictu and is characterized by shallow marine to aeolian deposits developed during both transgressive and highstand phases the following bay deposits of subunit 3b are associated with ois 5c 100 5 ky and record a second transgressive event t3 and highstand phase occurred during the neo tyrrhenian the succession of san giovanni di sinis ends with continental deposits of unit 4 associated to a sea level fall that took place at the beginning of the last glacial phase ois 4

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

chevron ridges and runup deposits in the bahamas from storms late in oxygen isotope substage 5e abstract landward pointing v shaped sand ridges several kilometers long are common along the windward margin of the bahama islands their axes share a northeast southwest trend internally the ridges contain low angle oolitic beds with few erosional truncations commonly interbedded are tabular fenestrae rich beds such as those formed by the sheet flow of water over dry sand defined here as chevron ridges these landforms appear to have originated in the rapid remobilization of bank margin ooid bodies by the action of long period waves from a northeasterly source deposits along adjacent coastlines also preserve evidence of the impact of large waves reworked eolian sand bodies preserve beach fenestrae and hydraulic scour traces up to 40 m on older ridges on cliffed coasts 1000 ton boulders have been thrown well inland recording the impact of large waves amino acid ratios confirm a correlation of the ridges across the archipelago while stratigraphy spacing and cross cutting relationships indicate emplacement as sea level fell rapidly from the substage 5e maximum at or above 6 m

late highstand patterns of shifting and stepping coastal barriers and washover fans late messinian sorbas basin se spain abstract the late messinian sorbas member up to 75 m thick consists in its type area of a parasequence set of three prograding coastal barriers sequences i iii associated with lagoon and washover sediments around the town of sorbas these strata can be studied exceptionally well due to absence of burrowing by raised messinian salinities and exposure along a network of up to 30 m deep canyons fifteen vertical sections were logged and carefully correlated this permits to reconstruct and discuss patterns of relative sea level movements between decimetres up to 15 m within a parasequence excellent examples of non tidal transgressive facies are characterized by lagoon and washover sediments instead of the usual combination of washover and tidal deposits channel and flood tidal delta implications for the sandstone connectivity are given the lower two sequences are deposited in a relatively large tectonically enhanced wedge shaped accommodation space they show both fining up deepening sequences followed by prograding coarsening up shoaling sequences and can be compared to the classical parasequences of the western interior basin usa progradation of sequence ii was interrupted by a major slide event most likely triggered by an earthquake which caused more than 400 m seaward slumping of a stretch of 1 km of coastal sands the architecture of sequence iii is more complex due to limited accommodation space characteristic for the late highstand so that this setting was very sensitive to sea level fluctuations this resulted in an intricate pattern of juxtaposed and superposed lagoonal muds washover fans and swash zones so called stranded coastal barriers occur which were left behind after seaward jump of the coastline over more than 1 5 km during forced regression the pattern of reconstructed sea level positions is well comparable to the sequential pattern shown by the correlated equivalents along the northern basin margin which belong to the so called terminal carbonate complex the problem of ranking the complex sequence iii as one or more parasequences and its consequences for cyclostratigraphy are shortly discussed two models of washover formation are given respectively during more rapid and more slow sea level rise the influence of synsedimentary folding on the location of barriers is discussed and also the source area of extra and intraclasts supplied to barriers and washovers after deposition of the sorbas member the sea withdrew from the sorbas basin probably as a result of the major downdrop in the mediterranean at the maximum isolation during the salinity crisis it is suggested that the semi enclosed setting of the basin resulted only in limited localized erosion in contrast to the deeper adjacent vera basin which was more open to the mediterranean

modelled atmospheric temperatures and global sea levels over the past million years the climate has passed through a series of glacials and interglacials over the past million years but the nature of this cyclicity in terms of temperature ice volume and sea level and the underlying causes are not well known bintanja et al use a new method to deduce a one million year time series of these variables the reconstructed records are much longer than other methods have provided for any of these variables individually the most intense glacial stages were 17 c colder than today and most of the continental ice was present in north america strong cooling in the beginning of glacials was found to precede ice sheet build up these findings may shed light on the causes of ice age cycles marine records of sediment oxygen isotope compositions show that the earth s climate has gone through a succession of glacial and interglacial periods during the past million years but the interpretation of the oxygen isotope records is complicated because both isotope storage in ice sheets and deep water temperature affect the recorded isotopic composition1 2 3 4 5 separating these two effects would require long records of either sea level or deep ocean temperature which are currently not available here we use a coupled model of the northern hemisphere ice sheets6 and ocean temperatures forced to match an oxygen isotope record for the past million years compiled from 57 globally distributed sediment cores to quantify both contributions simultaneously we find that the ice sheet contribution to the variability in oxygen isotope composition varied from ten per cent in the beginning of glacial periods to sixty per cent at glacial maxima suggesting that strong ocean cooling preceded slow ice sheet build up the model yields mutually consistent time series of continental mean surface temperatures between 40 and 80 n ice volume and global sea level we find that during extreme glacial stages air temperatures were 17 1 8 c lower than present with a 120 10 m sea level equivalent of continental ice present

some geological implications of average quaternary glacial conditions analyses of quaternary landscape evolution tend to focus on events associated with culminations of glacial and interglacial ages but for most of quaternary time environments were intermediate in character average quaternary glacial conditions based on assessment of the marine isotope record approximated those near the stage 2 stage 1 transition and during substages 5b and 5d isotope stages 3 and 4 and substages 5a d lie within one standard deviation of the mean value under average glacial conditions ice sheets lying over northern north america and europe were much more contracted than their full glacial counterparts and the distribution of mountain glaciers reflected a snowline depression of some 500 m geomorphic processes operating under average quaternary conditions contributed importantly to landscape evolution examples of landscapes that may represent such average conditions include cirques and fluvial deposits of the pacific northwest the fjords and strandflat of western norway and atolls of the tropical oceans by examining the geologic record from the perspective of average conditions rather than those of climatic extremes added insight can be gained regarding the evolution of quaternary landscapes

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

late pleistocene paleoclimates and sea level change in the mediterranean as inferred from stable isotope and u series studies of overgrowths on speleothems mallorca spain abstract phreatic overgrowths on speleothems form at the surface of brackish pools which are present in many coastal caves of mallorca spain unlike common vadose speleothems formed in subaerial environments their occurrence directly identifies the height of the sea level at the time of the carbonate deposition because such pools are physically connected with the sea these deposits from the late pleistocene have recorded the same global variations in oxygen isotopes as planktonic and benthonic foraminifera corals and cave deposits a number of phreatic overgrowths on speleothems have been dated using the th u method in order to determine the position of the sea level during late quaternary the same samples as well as some subaerial speleothems have been analysed for 18 o 16 o and 13 c 12 c ratios the former samples allow the analysis of variations in sea water component in the brackish pools associated with glacio eustatic mediterranean fluctuations and the latter permit inferences concerning past continental climate changes some high sea stands have been recognized in correspondence with oxygen isotope stages ois 9 or older 7 5e 5c and 5a phreatic overgrowths on speleothems have also been formed during a colder phase ois 4 demonstrating that also in that period there were environmental conditions favourable for this kind of carbonate precipitation vadose crystallizations have recorded a cold period at 36 ka corresponding with the end of ois 3

beach steps an evolutionary perspective abstract field observation of contrasting beach step behavior at canaveral national seashore on two subsequent days when incident wave conditions in the inner surf zone were similar prompted this re examination of our conceptual and quantitative understanding of beach steps these lower foreshore features are more complex than previously assumed evolving through erosional as well as accretional phases and displaying equifinality in geometric form but not necessarily internal sedimentary structure past and recent evidence is reviewed that links beach steps to incident waves at the surging plunging transition and to the action of a backwash vortex tides and low frequency waves likely play no direct role in beach step initiation although their presence can have pronounced influences on modulating nearshore hydrodynamics and thus on beach step maintenance and evolution a generalized conceptual model capturing these aspects of beach step dynamics is presented beach step initiation proceeds via step carving excavation or building depending on the erosional accretional character of the beach foreshore system subsequent evolution of the step form may take one of several alternative morphodynamic pathways including stepface retreat step drag down or step infilling elimination depending on tidal stage range or wave set up setdown additional data on equilibrium beach step forms and associated morphodynamic and hydrodynamic conditions in the field are necessary before quantitative models of beach step existence and evolution can be formulated with realistic results

joint inversion of lake floor electrical resistivity tomography and boat towed radio magnetotelluric data illustrated on synthetic data and an application from the aspo hard rock laboratory site sweden joint inversion of lake floor electrical resistivity tomography and boat towed radio magnetotelluric data illustrated on synthetic data and an application from the aspo hard rock laboratory site sweden

u and th concentrations and isotope ratios in modern carbonates and waters from the bahamas the short residence times of th and pa in seawater make them very responsive to changes in the ocean environment we use a new multi ion counting technique to make th and pa isotope measurements in seawaters from a near shore environment in which oceanic chemical tracers are not overwhelmed by terrestrial inputs the bahamas an unusual feature of the bahamas setting is the shallow depth of water residing on the bank tops these waters have significantly lower 232th 230th 10 000 than those immediately adjacent to the banks 24 000 31 000 and a 231pa 230th near the production ratio 0 1 the change in 232th 230th and 231pa 230th on the bank tops is explained by almost quantitative removal of th and pa by scavenging and their replacement with a mixture of 230th and 231pa alpha recoiled from the underlying carbonates together with th from dust dissolution analysis of a water profile in the tongue of the ocean which separates the great and little bahama banks allows us to trace the movement of bank top water to depth a distinct minimum in both 232th 230th 13 000 and 231pa 230th 0 5 is observed at 430 m and is interpreted to reflect density cascading of bank top water with entrained carbonate sediment these results suggest that th and pa can be used as water mass tracers in near shore environments uranium concentration measurements on the same waters demonstrate that u is conservative across a range in salinity of 2 psu with a concentration of 3 33 ppb at a salinity of 35 the incorporation of u and th isotopes into marine carbonates has also been assessed by analyzing carbonate samples from the same location as these bahamas waters such incorporation is critical for u th geochronology u isotope analyses demonstrate that seawater 234u averages 146 6 and does not vary by more than 2 5 o and that carbonates capture this value additional high precision measurements 1 o on modern carbonates confirm that all oceans have identical 234u modern marine carbonates are shown to have 232th 230th ratios that reflect the local seawater in which they formed

pleistocene coastal stratigraphy sea level highstands and neotectonism of the southern australian passive continental margin a review located in a tectonically stable intraplate setting and in the far field of former ice sheets the southern australian passive continental margin represents a globally important region for quantifying sea level during pleistocene highstands the stratigraphical record of the southern australian margin is dominated by geographically extensive coastal barrier estuarine and peritidal landforms of bioclastic temperate carbonate affinity a function of regional aridity siliciclastic successions dominate the eastern australian coastline despite the generally high level of tectonic stability regional contrasts are evident in the elevation of pleistocene shoreline deposits that largely relate to pre quaternary geotectonic setting the most complete record of pleistocene highstand deposits occurs in the murray basin coorong coastal plain region and indicates that interglacial sea level highstands for at least the past 11 interglacials did not deviate by more than 6 m from present sea level the pleistocene marginal marine record of southern australia is dominantly represented by coastal successions deposited during marine oxygen isotope stages 5e and 7 equating with relative sea level maxima of 2 6 m and greater than 1 m above present sea level apsl respectively intertidal facies of late pleistocene interstadial successions rarely occur above present sea level the most reliable record of glacio eustatic ice equivalent sea level is registered on coastlines developed on stable precambrian cratons such as the gawler craton eyre peninsula where a consistent elevation of 2 m apsl is registered for over 500 km for the last interglacial shoreline 125 ka copyright 2002 john wiley sons ltd

anomalous mis 7 sea level recorded on bermuda three new u series ages from coral fragments found in the belmont formation of bermuda fall in a range of 198 ka to 196 ka these late mis 7 ages are consistent with those of 201 ka and 199 ka measured in a previous study the disputed interpretation of the belmont formation as a unit that is allostratigraphically distinct from subsequent mis 5e deposits of the rocky bay formation is vindicated by a minimum age of 196 3 ka for the total of 6 coral fragments it has yielded emergent marine deposits of the belmont formation include sedimentary lithofacies that are considered to be reliable relative sea level indicators prominent among these is a facies representing the beach step a feature that develops sub tidally directly at the base of the swash zone from this facies and others preserved along 6 km of belmont formation coastal exposure it is concluded that mis 7 relative mean sea level reached 4 5 m and likely peaked at or above 6 0 m relative to present sea level at bermuda lower mis 7 sea level positions that are evidenced and that have been quoted in the past are considered transitory positions not maxima the mis 7 sea level elevations on bermuda reconstructed in this study are above the majority of those reported from elsewhere in the world this challenges the long standing notion of bermuda as a vertically stable tide gauge but is consistent with glacio hydroisostatic models which predict land mass subsidence at intermediate field sites such as bermuda at the end of long interglacials however because of evidence of instability at bermuda in the form of seismic activity and faulting which require further investigation judgement is reserved on the global implications of this palaeo sea level anomaly

variability in the uranium isotopic composition of the oceans over glacial interglacial timescales uranium series mass spectrometric analyses of corals from the uplifted last glacial terraces at huon peninsula papua new guinea that grew from 50 000 years ago to 30 000 years ago show systematically low values of 234u 238u at the time of coral growth compared with modern corals when combined with coral data from other studies a systematic trend emerges indicating shifts in the 234u 238u ratio at times of major glacial interglacial transitions that involve large variations in sea levels from last glacial to holocene the rate of change in 234u is approximately 1 per thousand years the variations in the u budget of the oceans appear to be due to accumulation of excess 234u in near shore areas in anoxic and suboxic sediments in salt marshes and mangroves in estuaries and in continental margins during periods of warm climate and high sea levels these near shore areas are exposed during periods of low sea level resulting in rapid oxidation of u into highly soluble phases the subsequent release of 234u enriched uranium into the oceans occurs over a sustained period in step with rising sea levels

a revised morpho and chronostratigraphy of the late and middle pleistocene coral reef terraces on southern barbados west indies the barbados coral reef terraces are one of the few type localities worldwide that provide insights into interglacial sea level change during the late and middle pleistocene several sea level estimates have been established since the late 1960s and each has contributed to the barbados model of sea level change this paper presents new morpho and chonostratigraphic data from the barbados coral reef terraces developed over the last 12 years the work is based on significant advances in electron spin resonance esr dating of fossil coral air photo interpretation and a greatly improved geomorphic map of preserved fossil beach formations and reef terraces above present sea level the need for a revision of past published morpho and chronostratigraphies is best demonstrated on the southern part of the island the morpho and chronostratigraphic sequence in this region is both more complex and diverse than has been assumed so far the revised morphostratigraphy presented here includes a differentiation of coral reef terraces wave cut platforms and other erosive features such as notches and cliffs our study of these geomorphic features combined with new numeric dating results esr u th enable a revised estimate of the spatial and temporal variation in tectonic uplift rate within south barbados these new rates are an essential requirement for more precise glacio eustatic sea level reconstructions during the late and middle pleistocene from this region

abrupt transitions during sustained explosive eruptions examples from the 1912 eruption of novarupta alaska plinian ignimbrite activity stopped briefly and abruptly 16 and 45 h after commencement of the 1912 novarupta eruption defining three episodes of explosive volcanism before finally giving way after 60 h to effusion of lava domes we focus here on the processes leading to the termination of the second and third of these three episodes early erupted pumice from both episodes show a very similar range in bulk vesicularity but the modal values markedly decrease and the vesicularity range widens toward the end of episode iii clasts erupted at the end of each episode represent textural extremes at the end of episode ii clasts have very thin glass walls and a predominance of large bubbles whereas at the end of episode iii clasts have thick interstices and more small bubbles quantitatively all clasts have very similar vesicle size distributions which show a division in the bubble population at 30 m vesicle diameter and cumulative number densities ranging from 107 109 cm 3 patterns seen in histograms of volume fraction and the trends in the vesicle size data can be explained by coalescence signatures superimposed on an interval of prolonged nucleation and free growth of bubbles compared to experimental data for bubble growth in silicic melts the high 1912 number densities suggest homogeneous nucleation was a significant if not dominant mechanism of bubble nucleation in the dacitic magma the most distinct clast populations occurred toward the end of plinian activity preceding effusive dome growth distributions skewed toward small sizes thick walls and teardrop vesicle shapes are indicative of bubble wall collapse marking maturation of the melt and onset of processes of outgassing the data suggest that the superficially similar pauses in the 1912 eruption which marked the ends of episodes ii and iii had very different causes through episode iii the trend in vesicle size data reflects a progressive shift in the degassing process from rapid magma ascent and coupled gas exsolution to slower ascent with partial open system outgassing as a precursor to effusive dome growth no such trend is visible in the episode ii clast assemblages we suggest that external changes involving failure of the conduit vent walls are more likely to have effected the break in explosive activity at 45 h

sea level history of the past two interglacial periods new evidence from u series dating of reef corals from south florida abstract as a future warm climate analog much attention has been directed to studies of the last interglacial period or marine isotope substage mis 5 5 which occurred 120 000 years ago nevertheless there are still uncertainties with respect to its duration warmth and magnitude of sea level rise here we present new data from tectonically stable peninsular florida and the florida keys that provide estimates of the timing and magnitude of sea level rise during the last interglacial period the last interglacial high sea stand in south florida is recorded by the key largo limestone a fossil reef complex and the miami limestone an oolitic marine sediment thirty five new high precision uranium series ages of fossil corals from the key largo limestone indicate that sea level was significantly above present for at least 9000 years during the last interglacial period and possibly longer ooids from the miami limestone show open system histories with respect to u series dating but show a clear linear trend toward an age of 120 ka correlating this unit with the last interglacial corals of the key largo limestone older fossil reefs at three localities in the florida keys have ages of 200 ka and probably correlate to mis 7 these reefs imply sea level near or slightly above present during the penultimate interglacial period elevation measurements of both the key largo limestone and the miami limestone indicate that local relative sea level was at least 6 6 m and possibly as much as 8 3 m higher than present during the last interglacial period

aminostratigraphy and ages of pleistocene limestones of bermuda the pleistocene stratigraphy of bermuda offers important information for sea level history corals are rare in bermuda pleistocene carbonates and so many deposits are not appropriate for u series dating we have extended the geochronological base in bermuda by determining the extent of isoleucine epimerization a i ratios in 1 marine shells glycymeris and others from deposits of sea level high stands 2 land snails poecilozonites from protosols associated with the eolianites that comprise the bulk of bermuda and 3 whole rock samples of bioclastic calcarenites the three distinct types of samples provide independent aminostratigraphies aminozones c e f g h j and k that are mutually consistent and in agreement with the mapped lithostratigraphy correlation of the amino acid ratios with ages based on previously published u series coral dates verifies the utility of the apparent parabolic kinetics model for estimation of amino acid racemization ages extrapolation of ages based on the model to deposits beyond the range of u series dating reveals that a significant middle pleistocene section is present in bermuda

u series and amino acid racemization geochronology of bermuda implications for eustatic sea level fluctuation over the past 250 000 years abstract bermuda is a stable mid oceanic carbonate platform for which a particularly complete record of late pleistocene eustatic sea level fluctuation has been reconstructed from a detailed study of geological field relationships combined with an extensive programme of u series and amino acid racemization geochronology only twice in the past 250 000 yr has sea level in bermuda been above its present level once at approximately 200 k y when it stood at about 2 m and most recently at 125 4 k y when it stood at 5 1 m these times of interglacial high sea level are characterized by the development of patch reefs and marine calcarenites at elevations above present sea level episodes of lower sea stand onto the bermuda platform at elevations higher than 20 m are observed within the two interglacial periods and are characterized by the deposition of eolianites by contrast glacial periods are times of residual soil formation and deposition of speleothems in caves at elevations below present sea level excellent correlation is observed between the bermuda glacio eustatic sea level record and other marine and terrestrial paleoclimate records

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

ice volume and sea level during the last interglacial during the last interglacial period 125 000 years ago sea level was at least several meters higher than at present with substantial variability observed for peak sea level at geographically diverse sites speculation that the west antarctic ice sheet collapsed during the last interglacial period has drawn particular interest to understanding climate and ice sheet dynamics during this time interval we provide an internally consistent database of coral u th ages to assess last interglacial sea level observations in the context of isostatic modeling and stratigraphic evidence these data indicate that global eustatic sea level peaked 5 5 to 9 meters above present sea level requiring smaller ice sheets in both greenland and antarctica relative to today and indicating strong sea level sensitivity to small changes in radiative forcing

antarctic temperature and global sea level closely coupled over the past five glacial cycles sea level has varied by over one hundred metres across glacial interglacial cycles over the past 520 000 years an extended sea level reconstruction shows a strong coupling between these sea level changes and antarctic surface temperatures over the past five glacial cycles

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

maximum sea levels for the last glacial period from u series ages of submerged speleothems pleistocene sea levels reflect changes in the surface distribution of land sea and ice which in turn significantly influence the earth s climate1 the most complete record of sea levels for the last glacial cycle has come from raised coral reef terraces of the huon peninsula papua new guinea2 4 but interpretation of this record is hampered by relatively large age uncertainties and the possibility of variation in the rate of tectonic uplift subaerial speleothems stalagmites stalactites and flowstones from submerged caves in tetonically stable areas provide an alternative source of data5 8 as their growth stops when rising sea levels flood the caves previous studies of speleothems have been limited by dating precision5 6 and sample availability5 7 here we present high precision thermal ionization mass spectrometric 230th ages9 11 for a comprehensive suite of speleothem samples from the bahamas our results provide a record of maximum elevation of sea levels for the period from 80 to 10 kyr before the present for much of which sea levels are poorly known we also find that regional palaeoclimatic change can be an important factor in the termination of speleothem growth

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

phasing and amplitude of sea level and climate change during the penultimate interglacial the penultimate interglacial period was punctuated by three sea level highstands uranium thorium ages obtained from speleothems in italian caves show that the relationship between the timing of the peaks in sea level and northern hemisphere insolation is dependent on the previous extent of continental ice sheets