evidence from u th dating against northern hemisphere forcing of the penultimate deglaciation milankovitch proposed that summer insolation at mid latitudes in the northern hemisphere directly causes the ice age climate cycles1 this would imply that times of ice sheet collapse should correspond to peaks in northern hemisphere june insolation but the penultimate deglaciation has proved controversial because june insolation peaks 127 kyr ago whereas several records of past climate suggest that change may have occurred up to 15 kyr earlier2 3 4 5 6 7 8 there is a clear signature of the penultimate deglaciation in marine oxygen isotope records but dating this event which is significantly before the 14c age range has not been possible here we date the penultimate deglaciation in a record from the bahamas using a new u th isochron technique after the necessary corrections for recoil mobility of 234u and 230th and a small age correction for sediment mixing the midpoint age for the penultimate deglaciation is determined to be 135 2 5 kyr ago this age is consistent with some coral based sea level estimates but it is difficult to reconcile with june northern hemisphere insolation as the trigger for the ice age cycles potential alternative driving mechanisms for the ice age cycles that are consistent with such an early date for the penultimate deglaciation are either the variability of the tropical ocean atmosphere system or changes in atmospheric co2 concentration controlled by a process in the southern hemisphere

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

recognition of non milankovitch sea level highstands at 185 and 343 thousand years ago from u th dating of bahamas sediment abstract thirty one new bulk sediment u th dates are presented together with an improved 18o stratigraphy for odp site 1008a on the slopes of the bahamas banks these ages supplement and extend those from previous studies and provide constraints on the timing of sea level highstands associated with marine isotope stages mis 7 and 9 ages are screened for reliability based on their initial u and th isotope ratios and on the aragonite fraction of the sediment twelve reliable dates for mis 7 suggest that its start is concordant with that predicted if climate is forced by northern hemisphere summer insolation following the theory of milankovitch but u th and 18o data indicate the presence of an additional highstand which post dates the expected end of mis 7 by up to 10 ka this event is also seen in coral reconstructions of sea level it suggests that sea level is not responding in any simple way to northern hemisphere summer insolation and that tuned chronologies which make such an assumption are in error by 10 ka at this time u th dates for mis 9 also suggest a potential mismatch between the actual timing of sea level and that predicted by simple mid latitude northern hemisphere forcing four dates are earlier than that predicted for the start of mis 9 although the most extreme of these dates may not be reliable based on the low aragonite content of the sediment the other three appear robust and suggest that full mis 9 interglacial conditions were established at 343 ka this is 8 ka prior to the date expected if this warm period were driven by northern hemisphere summer insolation

open system coral ages reveal persistent suborbital sea level cycles sea level is a sensitive index of global climate that has been linked to earth s orbital variations with a minimum periodicity of about 21 000 years although there is ample evidence for climate oscillations that are too frequent to be explained by orbital forcing suborbital frequency sea level change has been difficult to resolve primarily because of problems with uranium thorium coral dating here we use a new approach that corrects coral ages for the frequently observed open system behavior of uranium series nuclides substantially improving the resolution of sea level reconstruction this curve reveals persistent sea level oscillations that are too frequent to be explained exclusively by orbital forcing

neogene quaternary slow coastal uplift of western europe through the perspective of sequences of strandlines from the cotentin peninsula normandy france abstract the cotentin peninsula normandy france displays sequences of marine terraces and rasas the latter being wide late cenozoic coastal erosion surfaces that are typical of western european coasts in portugal spain france and southern england remote sensing imagery and field mapping enabled reappraisal of the cotentin coastal sequences from bottom to top the n cotentin sequence includes four previously recognized pleistocene marine terraces t1 to t4 at elevations

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

records of cosmogenic radionuclides 10be 26al and 36cl in corals first studies on coral erosion rates and potential of dating very old corals we present results of measurements of cosmogenic 10 be 26 al and 36 cl and the indigenous intrinsic concentrations of the stable elements be al and cl in 120 200 kyr old corals from barbados and puerto rico the concentration levels of these radionuclides in the corals lie in the range 10 4 to 10 8 atoms g a comparison of the measured nuclide concentrations with those expected to be produced in the corals by nuclear interactions of energetic cosmic radiation shows that i the radionuclides 26 al and 36 cl are derived from in situ cosmic ray interactions in the corals after their formation but that ii the radionuclide 10 be owes its provenance in the coralline lattice primarily due to incorporation of dissolved beryllium in seawater in the lattice structure of the corals copyright 2005 elsevier ltd we discuss production rates and potential uses of cosmogenic radionuclides in corals and the implications of the measure ments reported here on the concentration of the cosmogenic radionuclides 10 be 26 al and 36 cl we show that the latter two radionuclides serve as gauges of coral terrace erosion rates whereas the cosmogenic 10 be is suitable for determining the ages of old corals of ages exceeding a few million years up to 10 myr the erosion rates of the corals range from 0 7 to 5 10 3 cm yr corresponding to an appreciable surface loss after aerial exposure 1 3 m since the last interglacial and 8m since the penultimate interglacial

quantitative analysis of the extensional tectonics of tharsis bulge mars geodynamic implications about 10 of the tharsis bulge surface is intensely faulted with a fault density up to 1 fault km in these intensely faulted areas 54 impact craters which exhibit faulted walls and floor are now elliptical in shape these ellipticities indicate an average strain value of 10 inside these provinces this strain value is 4 times greater than the strain deduced from normal fault morphometric analysis this high value indicates that the strain is not only due to 60 dip normal faults and that some additional tectonic processes exist such as boudinage this important strain value corresponds to an elongation of about 50 km across thaumasia and tempe mareotis provinces and 20 km across alba patera regio the amount of elongation for the entire tharsis region is 2 orders of magnitude higher than the strains and motions related to standard models of bulge formation these intensely faulted areas are restricted areas where faults are both radial to the bulge and perpendicular to the topographic slope the stretching does not influence the regional topography and there are no topographic shoulders or important level differences between faulted and nonfaulted areas which would indicate that the crust is not thinned under the stretched provinces outside these intensely faulted areas the graben width is remarkably constant all over the tharsis bulge indicating the existence of a brittle ductile transition or an incompetent level at about 1 2 km below the surface a new origin for the tharsis tectonic features is proposed as a preliminary hypothesis the intensely faulted areas correspond to the uphill parts and to denudation zones of gravity slidings which move on a 2km deep incompetent level the gliding of the slab on the very low dipping flanks of tharsis needs three conditions 1 the viscosity of the incompetent layer must be equal to the viscosity of the ice 2 the brittle layer must have been previously faulted by the bulging itself 3 these preexisting radial fault directions must be perpendicular to topographic slope the ridged plain units in lunae palus and coprates provinces thus correspond to a zone of blocking inside the gliding slab due to an interruption of the decollement level

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

late quaternary molluscs from the northern san matias gulf northern patagonia argentina southwestern atlantic faunistic changes and paleoenvironmental interpretation the late quaternary in the coastal area of south america is represented mostly by littoral ridges cliffs and tidal plains with associated remains of gastropods and bivalves currently used as paleoclimatic indicators the aim of this study is to characterize the assemblages of molluscs bivalves and gastropods both pleistocene mis 9 mis 7 mis 5e and holocene mis 1 from the northern san matias gulf northern patagonia argentina in the southwestern atlantic ocean in order to assess whether faunal change occurred together with late quaternary climatic change twenty localities were studied seven from different interglacial stages of the pleistocene six holocene and seven modern beaches in which 42 species were recorded 20 bivalves and 22 gastropods among bivalves euryhaline infaunal from sandy substrates and filter feeders prevail amiantis purpurata is the dominant species of the whole mollusc assemblage among gastropods although also euryhaline the epifaunal species of rocky and sandy substrates and carnivores prevail on the basis of descriptive statistical analyses bray curtis and ac methods the localities formed three groups according to ages modern vs pleistocene and holocene and or presence abundance of species 70 of the marine malacofauna of mis 7 remains during mis 5e decreasing to 60 during mis 1 and to 27 when compared to the modern beaches the most notable changes in the distribution of the species were tegula atra currently extinct in the argentine atlantic coast but recorded in pleistocene interglacials mis 7 and mis 5e anomalocardia brasiliana which only appeared in mis 5e and mesodesma mactroides in mis 1 mis 5e was likely the warmest stage within the period considered followed by mis 7 both with higher sst temperatures than the present ones and since mis 1 molluscs of temperate cold lineages of the magellan malacological province are recorded

234u 238u mass spectrometry of corals how accurate is the uth age of the last interglacial period direct measurement of u and th by mass spectrometry recently provided a spectacular improvement in the precision of coral dating by the uth disequilibrium method 1 mass spectrometric data also provide a much better resolution for the examination of subtle diagenetic effects revealed by small variations of the 234u 238u ratio such perturbations may strongly affect the accuracy of the uth chronometer a compilation of all the corals analyzed to date by mass spectrometry shows that most of the corals from terraces of the last interglacial have initial 234u 238u ratios higher than present day seawater in contrast to modern holocene and last glacial corals some samples that have very high 234u 238u initial ratios up to 1 2 and high u concentrations up to 4 ppm were probably contaminated by continental groundwaters however even apparently pristine samples have 234u 238u initial ratios which are still slightly higher than present day seawater mean value 1 160 compared to 1 140 1 150 2 with little overlap between the two distributions this difference in the u initial ratio raises some uncertainty about the accuracy of the uth age determinations of these corals in spite of the fact that the 234u230th ages cluster in a narrow range between 122 and 133 kyr the data could also be interpreted as resulting from slight contamination of corals that are significantly older than 125 kyr two possible explanations may explain these data 1 all these samples may have been diagenetically altered since they all come from surface outcrops which have been directly exposed to precipitations or soil waters for 125 kyr in this case the true age of these corals remains uncertain depending on the timing of the alteration process i e initial late or continuous 2 the second possibility is that some of the differences in 234u 238u ratios measured in 125 kyr cold corals compared to modern seawater may be due to a higher 234u 238u ratio in seawater 125 kyr ago this could result from temporal variations in the weathering regimes of continental land masses

hypocentral relocation using clustering along planes constraints implications for fault geometry summary hypocentre location is an ill posed inverse problem even assuming that the velocity model is known because different sets of hypocentre locations may satisfy the fitting criterion we present a regularized hypocentre inversion in which the constraints of spatial proximity of the hypocentres to target planes are used this constraint introduces the geological bias that earthquakes might occur along fault planes here the target planes may be either 1 planes specified by the interpreter or 2 planes fitting groups of events we assume also that initial estimates of hypocentres and origin times are available then the initial hypocentre estimates origin times and target planes are used as input to an inversion problem to relocate the hypocentres so that the maximum possible clustering of events along the given planes is attained matching the observed traveltimes we use l1 norm for data fitting l2 norm for the plane proximity criterion and a polytope algorithm to minimize the functional results from synthetic and real data indicate that the plane proximity constraint allows for hypocentre relocation presenting a high degree of clustering along planes the real data example is an intraplate earthquake sequence in ne brazil our methodology defined the geometry and strike of fault segments close to known geology and focal mechanism data in addition the new method indicates that the fault is characterized by a splay geometry in its southern end and that more than three fault segments are necessary to explain the hypocentre distribution

start of the last interglacial period at 135 ka evidence from a high alpine speleothem a detailed study of growth periods of a flowstone from spannagel cave in the zillertal alps austria at 2500 m above sea level a site highly sensitive to climate changes offers unprecedented new insights into pleistocene climate change in central europe flowstone sample spa 52 has a high u content to 116 ppm analyses of this sample reveal that episodes of calcite deposition started at 204 3 ka 135 1 2 ka and 122 ka suggesting that at these times the mean air temperature at this high alpine site was within 1 5 c of the present day condition the beginning of growth at 135 ka corresponds to the ending of the last glaciation and is concordant with a midpoint age for the penultimate deglaciation at 135 2 5 ka as deduced from the absolutely dated oxygen isotope curve in sediments from the bahamas as well as with recent coral evidence from barbados indicating a high sea level already by 135 8 0 8 ka this set of data supports evidence against northern hemisphere forcing of termination ii because the insolation maximum is at 127 ka

early mid holocene climatic variations in tasmania australia multi proxy records in a stalagmite from lynds cave mass spectrometric uranium series dating and c o isotopic analysis of a stalagmite from lynds cave northern tasmania australia provide a high resolution record of regional climate change between 5100 and 9200 yr before present bp combined delta 18 o delta 13 c growth rate initial u 234 u 238 and physical property color transparency and porosity records allow recognition of seven climatic stages stage i 9080 yr bp a relatively dry period at the beginning of stalagmite growth evidenced by elevated u 234 u 238 stage ii 9080 8600 yr bp a period of unstable climate characterized by high frequency variability in temperature and bio productivity stage 111 8600 8000 yr bp a period of stable and moderate precipitation and stable and high bio productivity with a continuously rising temperature stage iv 8000 7400 yr bp the warmest period with high evaporation and low effective precipitation rainfall less evaporation stage v 7400 7000 yr bp the wettest period with highest stalagmite growth and enhanced but unstable bio productivity stage vi 7000 6600 yr bp a period with a significantly reduced precipitation and bio productivity without noticeable change in temperature stage vii 6600 5100 yr bp a period of lowest temperature and precipitation marking a significant climatic deterioration overall the records suggest that the warmest climate occurred between 8000 and 7400 yr bp followed by a wettest period between 7400 and 7000 yr bp these are broadly correlated with the so called mid holocene optimum previously proposed using pollen and lake level records however the timing and resolution of the speleothem record from lynds cave are significantly higher than in both the pollen and lake level records this allows us to correlate the abrupt change in physical property delta 18 o delta 13 c growth rate and initial u 234 u 238 of the stalagmite at similar to8000 yr bp with a global climatic event at early mid holocene transition c 2001 elsevier science b v all rights reserved

climate and vegetation changes 180 000 to 345 000 years ago recorded in a deep sea core off portugal a new high resolution combined marine proxy pollen sequence from the portuguese margin md01 2443 enables direct comparison of ocean and ice volume changes with vegetation development in south west iberia during marine isotope stages mis 7 8 and 9 changes in sea surface conditions on both orbital and millennial time scales are closely mirrored by forest extent indicating a coherence of climate variability between the north atlantic and south west iberia deglacial warming at the start of mis 7 and 9 was interrupted by incursions of subpolar water masses at the site accompanied by reversals in tree population expansion during mis 7e and 9e the close relationship in timing and amplitude between vegetation and offshore conditions broke down early forest collapse points to pronounced cooling and aridification on land which although not accompanied by a change in water masses at the portuguese margin appears to have coincided with abrupt decreases in atmospheric methane concentration recorded in antarctic ice cores the most extreme glacial conditions of mis 8 occurred during the early part followed by an interval of warmer conditions and tree population expansion similar to 263 ka this has sometimes been considered as indicating an early deglaciation but the data presented here show that it was distinct from termination iii which occurred later in line with milankovitch forcing a sub orbital oscillation in both isotopic and pollen records is observed at the end of mis 7 ca 184 ka which appears to be coeval with a recently identified sea level high stand c 2006 elsevier b v all rights reserved

comparison of changes in vegetation in northeast greece with records of climate variability on orbital and suborbital frequencies over the last 450 000 years abstract a new direct pollen orbital tuning procedure based on a correspondence between changes in certain vegetation elements and march and june perihelion configurations is applied to the tenaghi philippon record northeast greece the development of a refined chronological scheme allows comparisons to be made with records of climate variability from the north atlantic as well as of global sea level ice volume and atmospheric co2 content on orbital frequencies the comparison reveals a close correspondence between relative ice volume extent and tree population size during glacial intervals during interglacial and interstadial periods the degree of forest development is more closely associated with high latitude insolation and related climate regimes rather than extent of residual ice volume on suborbital frequencies the greek record shows similar repeat times in peaks of steppe vegetation with north atlantic ice rafting events but the amplitude of this variability in the two records is not always proportional overall what emerges is that the major shifts in the relative abundance of forest v open vegetation communities at tenaghi philippon on orbital and suborbital frequencies over the last 450 000 years are coherent with high latitude changes affecting atmospheric and oceanic circulation glacial decreases in atmospheric co2 content contributed to the elimination of tree populations by exacerbating water stress conditions during arid intervals but do not appear to be the primary driver of the observed vegetation changes at this latitude variations in co2 levels in the order of 40 ppmv between different interglacial interstadials periods with adequate moisture availability appear to have had a limited effect on the nature and size of tree populations

234u 238u ratios and230th ages for hateruma atoll corals implications for coral diagenesis and seawater234u 238u ratios published results for corals that are more than ca 50 ka old from for example barbados and vanuata often yield initial 234u 238u activity ratios that are significantly greater than 1 144 0 004 the value for modern seawater this study reports results for corals from hateruma atoll japan and investigates the effects of diagenesis on the initial 234u 238u ratios of the corals hateruma consists of over 95 reef material of less than 500 ka in age because groundwaters associated with recent carbonates tend not to have elevated 234u 238u ratios the scope for increasing the 234u 238u ratios of hateruma corals through groundwater interaction should be minimal the corals examined range from those which show no petrographic or x ray evidence for diagenetic alteration and are pristine to those containing secondary cements of either aragonite or high or low mg calcite these various phases have been mechanically separated and analysed in agreement with previous assertions the analyses of these separates demonstrates that the presence of calcite should be a cause for rejection of coral samples it is also shown that aragonite cement can form later than coral death and may bias estimates of age and initial 234u 238u ratios of the six pristine corals three have anomalous 230th 238u ratios requiring u loss and or230th addition the remaining fifteen of the eighteen total analyses reported here yield ages from 1 6 ka to 260 ka no evidence for an increase in 234u 238u ratios in past seawater from this period has been found the best estimates for 234u 238u ratios are close to the current seawater value

sea level during the penultimate interglacial period based on a submerged stalagmite from argentarola cave italy accurate constraints are presented for the absolute age duration and sea level for the highstand corresponding to marine isotope stage mis 7 1 our work is based on a stalagmite collected in a currently submerged cave from italy argentarola cave flooding of this coastal cave is clearly marked within the stalagmite by a thick marine overgrowth of serpulid worms precise uranium thorium u th ages measured by thermal ionization mass spectrometry suggest that the stalagmite growth varied in phase with climate during mis 7 2 and mis 6 the penultimate glacial period in addition the period of marine transgression is bracketed between 202 and 190 kyr bp defining a mis 7 1 duration of 11 2 kyr comparison with previous studies provides a new constraint on the sea level during mis 7 1 that has approximately remained between 318 and 39 m relative to present sea level the timing of the mis 7 1 highstand is in full agreement with the specmap chronology which contrasts with the growing body of evidence showing a significant phase difference for mis 5 5 a tempting conclusion is that second order sea level highstands such as mis 7 1 may be purely driven by astronomical changes in contrast with major terminations such as termination ii atmospheric co2 levels may partly explain this contrast since the two sea level transitions mis 7 2 7 1 and mis 6 5 5 are characterized by very different co2 rises 20 vs 100 ppm fl 2002 elsevier science b v all rights reserved

did glacials start with global warming abstract correlation of paleoclimatic evidence with orbital changes shows that the build up of polar ice accelerated when low obliquity coincided with perihelion in northern hemisphere winter under low obliquity the insolation was channeled to the tropics at the expense of both polar caps as perihelion moved from winter solstice toward spring equinox the solar beam in astronomic winter and spring became stronger than in summer and autumn this orbital configuration under climate conditions like today would lead to warming of tropical oceans but cooling of the polar regions the areally weighted global mean surface temperature which is dominated by the low latitudes would increase consequently during the first millennia the early glacial ice build up was most likely accompanied by global warming it was the associated increase of meridional insolation and temperature gradients which were instrumental in the transition to a glacial a significant part of the current global warming is due to the gradual temperature increase of the tropical oceans as the changing orbital configuration today resembles that of the last interglacial glacial transition the warming is likely to have a natural component

uranium series dating of fossil coral reefs extending the sea level record beyond the last glacial cycle abstract absolutely dated records of past sea level change are extremely important for understanding the advance and retreat of the large ice sheets when combined with other complementary climate archives and climate models such records offer the potential to gain an improved understanding of earth s natural climate cycles providing a firmer basis for assessing the role of anthropogenic effects such as greenhouse gas emissions in modifying climate the u series dating of fossil coral reefs has been widely utilized to provide absolutely dated records of past sea level change and numerous observations now exist for the past 130 000 years spanning the last glacial cycle despite this controversies still exist regarding the exact timing and character of sea level events within this time interval and extending the sea level history further back in time on the basis of robust and independent age constraints for older fossil reefs remains very elusive this is primarily due to a progressive loss in the resolution of the u series chronometer as one goes further back in time coupled to a lack of well preserved dateable coral in older fossil reefs to overcome these limitations the primary challenges are three fold first new analytical protocols are required to improve the resolution of the u series chronometer enhanced analytical precision must be coupled to accuracy through continued refinement of the u series decay constant determinations and via the implementation of rigorous inter laboratory calibration exercises second efforts should continue to be focussed on gaining an improved understanding of the mechanisms controlling open system exchange of the u series isotopes in fossil reef systems this will allow the number of reliable u series observations to be extended third alternative dateable archives of past sea level change must continue to be emphasized to further complement the coral reef database these limitations are discussed in the context of current developments that further advance the application of u series chronology to older fossil reef systems formed prior to the last glacial cycle

links between climate and sea levels for the past three million years the oscillations between glacial and interglacial climate conditions over the past three million years have been characterized by a transfer of immense amounts of water between two of its largest reservoirs on earth the ice sheets and the oceans since the latest of these oscillations the last glacial maximum between about 30 000 and 19 000 years ago approximately 50 million cubic kilometres of ice has melted from the land based ice sheets raising global sea level by approximately 130 metres such rapid changes in sea level are part of a complex pattern of interactions between the atmosphere oceans ice sheets and solid earth all of which have different response timescales the trigger for the sea level fluctuations most probably lies with changes in insolation caused by astronomical forcing but internal feedback cycles complicate the simple model of causes and effects

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

mass spectrometric 230th 234u 238u dating of the devils hole calcite vein the devils hole calcite vein contains a long term climatic record but requires accurate chronologic control for its interpretation mass spectrometric u series ages for samples from core dh 11 yielded 230 th ages with precisions ranging from less than 1 000 years 2 for samples younger than 140 ka thousands of years ago to less than 50 000 years for the oldest samples 566 ka the 234 u 238 u ages could be determined to a precision of 20 000 years for all ages calcite accumulated continuously from 566 ka until 60 ka at an average rate of 0 7 millimeter per 10 3 years the precise agreement between replicte analyses and the concordance of the 230 th 238 u 234 u 238 u ages for the oldest samples indicate that the dh 11 samples were closed systems and validate the dating technique in general

orbital tuning chronology for the vostok climate record supported by trapped gas composition abstract we present data on the o2 n2 ratios of trapped gas samples for the entire length of the vostok climate record as in other cores o2 n2 ratios in these samples are less than the atmospheric ratio by a small and variable amount because o2 is selectively excluded during the gas trapping process and because o2 is also preferentially lost in poorly preserved core samples samples younger than 150 ka have large and variable o2 depletions samples older than 200 ka have o2 n2 ratios that replicate well and vary smoothly with depth we plot o2 n2 ratios of well replicated samples older than 160 ka using a chronology derived by matching the 18o of paleoatmospheric o2 18oatm to northern hemisphere june insolation on this timescale o2 n2 varies coherently with local 78 s summertime insolation based on time series analysis of the o2 n2 record and the dynamics of snow metamorphism at the surface we conclude that summertime insolation influences physical properties of ice grains that control the degree of o2 exclusion during bubble closeoff o2 n2 in vostok is thus arguably a property that records local summertime insolation and can be used to test independent chronologies for the core we show that the 18oatm chronology supported by the coincidence of o2 n2 ratios with insolation is also compatible with recent radiometric dating of corals from high sea stands we further successfully test the 18oatm tuning chronology by showing that it predicts a chronology for the gisp2 core which is essentially indistinguishable from the standard gisp2 chronology and therefore in excellent agreement with the radiometric chronology of hulu cave china an accurate chronology for the vostok ice core is now in place

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

insights into north atlantic deep water formation during the peak interglacial interval of marine isotope stage 9 mis 9 foraminifera abundance and stable isotope records from odp site 984 61 25 n 24 04 w 1648 m in the north atlantic are used to reconstruct surface circulation variations and the relative strength of the north atlantic deep water nadw formation over the period spanning the peak warmth of marine interglacial stage mis 9e 324 336 ka this interval includes the preceding deglaciation termination 4 t4 and the subsequent glacial inception of mis 9d the records indicate a greatly reduced contribution of nadw during t4 as observed in more recent deglaciations in contrast with the most recent deglaciation the lack of a significant nadw signal extended from t4 well into the peak interglacial mis 9e and persisted nearly until the transition to the subsequent glacial stage mis 9d although nadw formation resumed during mis 9e only depths greater than 2000 m appear to have been ventilated the poorly ventilated intermediate depth of site 984 2000 m may have resulted on one hand from a general reduction of deep water ventilation by nadw during the study interval or on the other hand from different pathways of the spread of newly formed nadw that bypassed the study location the intermediate depths may have also been invaded by southern sourced waters as the formation of intermediate depth nadw weakened the absence of any significant nadw signal at the water depth of site 984 during the climatic optimum contrasts sharply with subsequent interglacial peaks mis 5e and the holocene despite the perturbed intermediate depth circulation oceanic heat transport northeastward was not interrupted and may have contributed to the relatively mild interglacial conditions of mis 9e

an open system model for u series age determinations of fossil corals the source of excess 234u in fossil corals and its relationship to u series age determinations has been an outstanding problem in geochronology for more than 20 years with increasing numbers of u series isotope measurements in corals and significant improvements in analytical precision through mass spectrometry it is increasingly apparent that a substantial fraction of observed isotope ratios cannot be reasonably explained by closed system decay moreover observations of a positive correlation between 234u 238u and 230th 238u ratios in corals from the same terrace are difficult to explain however the decay of dissolved uranium and recoil mobilization of uranium daughters produce particle reactive 234th and 230th and the coupled addition of these th isotopes could simultaneously increase coral 234u 238u and 230th 238u here we present a quantitative model based on decay dependent redistribution of 234th and 230th permitting calculation of open system coral ages these equations provide a general solution to the recoil redistribution problem applicable to any alpha decay series while measured isotope ratios of corals from the three youngest stratigraphically defined barbados terraces are inconsistent with closed system decay they fall in broadly linear arrays agreeing with model predictions isotopic arrays of older barbados corals and corals from terraces around the world are also consistent with model predictions suggesting the open system model is generally applicable corals with extreme isotopic compositions that are impossible to produce by closed system decay are consistent with the limited range of isotopic compositions predicted by the model at ages older than 600 ka for corals from a single terrace 234th and 230th redistribution appears to be a source of systematic conventional age error even for corals with slightly elevated 234u however open system ages are consistent even for corals with extremely elevated 234u for the youngest three barbados terraces mean open system terrace ages are consistent with mean conventional terrace ages calculated from pristine samples if the most accurate conventional ages are from corals with an initial 234u 238u identical to modern seawater then the open system model will improve the accuracy of coral u series age determinations and dramatically increase the number of reliable ages

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

uranium series dating of marine and lacustrine carbonates of the possible uranium series dating schemes the most important and most widely applied to marine carbonates is 230th dating with 231pa dating playing an increasingly important role for this reason this review will focus on these two methods 230th dating also referred to as u th dating or 238u 234u 230th dating involves calculating ages from radioactive decay and ingrowth relationships among 238u 234u and 230th 232th is also typically measured as a long lived essentially stable index isotope over the time scales relevant to 230th dating at present 230th dating can in principle be used to date materials as young as 3 years and in excess of 600 000 years edwards et al 1987a 1993 edwards 1988 see stirling et al 2001 for an example of dating corals in excess of 600 000 years old 231pa dating also referred to as u pa dating involves calculating ages from the ingrowth of 231pa from its grandparent 235u at present 231pa dating can be used to date materials as young as 10 years and as old 250 000 years edwards et al 1997 230th dating covers all of the 231pa time range and more with somewhat higher precision and is therefore the method of choice if a single method is applied however the combination of 231pa and 230th dating is of great importance in assessing possible diagenetic mobilization of the pertinent nuclides and thereby the accuracy of the ages allegre 1964 ku 1968 even if the primary age exceeds the 250 000 year limit of 231pa dating the combined methods can be used to assess the degree to which the samples have remained closed over the past 250 000 years e g edwards et al 1997 thus

u th systematics and 230th ages of carbonate chimneys at the lost city hydrothermal field the lost city hydrothermal field lchf is a serpentinite hosted vent field located 15 km west of the spreading axis of the mid atlantic ridge in this study uranium thorium u th geochronological techniques have been used to examine the u th systematics of hydrothermal fluids and the 230th ages of hydrothermally precipitated carbonate chimneys at the lchf fluid sample analyses indicate that endmember fluids likely contain only 0 0073 ng g u or less compared to 3 28 0 03 ng g of u in ambient seawater for fluid samples containing only 2 21 ambient seawater 1 1 11 mmol kg mg th concentration is 0 11 0 13 pg g and surrounding seawater concentrations average 0 133 0 016 pg g the 230th 232th atomic ratios of the vent fluids range from 1 10 10 6 to 11 5 10 6 are less than those of seawater and indicate that the vent fluids may contribute a minor amount of non radiogenic 230th to the lchf carbonate chimney deposits chimney 238u concentrations range from 1 to 10 g g and the average chimney corrected initial 234u is 147 2 0 8 which is not significantly different from the ambient seawater value of 146 5 0 6 carbonate 232th concentrations range broadly from 0 0038 0 0003 to 125 16 ng g and 230th 232th atomic ratios vary from near seawater values of 43 8 10 6 up to 530 25 10 3 chimney ages corrected for initial 230th range from 17 6 yrs to 120 13 kyrs the youngest chimneys are at the intersection of two active steeply dipping normal faults that cut the atlantis massif the oldest chimneys are located in the southwest portion of the field vent deposits on a steep fault bounded wall on the east side of the field are all 4 kyrs old indicating that mass wasting in this region is relatively recent comparison of results to prior age dating investigations of submarine hydrothermal systems shows that the lchf is the most long lived hydrothermal system known to date it is likely that seismic activity and active faulting within the atlantis massif and the atlantis fracture zone coupled with volumetric expansion of the underlying serpentinized host rocks play major roles in sustaining hydrothermal activity at this site the longevity of venting at the lchf may have implications for ecological succession of microorganisms within serpentinite hosted vent environments

high precision u series measurements of more than 500 000 year old fossil corals robust independent age constraints on the absolute timing of climate events based on the u series dating of fossil coral are sparse before the last glacial cycle using multiple collector inductively coupled plasma mass spectrometry with multiple faraday protocols we are able to date 600 ka samples with an uncertainty of better than 15 ka 2 representing a three fold improvement in precision compared with previous techniques using these methods we report u series measurements for a suite of 500 thousand year old ka corals from henderson island an emergent atoll in the south central pacific ocean the fossil corals show extraordinarily little diagenetic alteration for their age and the best preserved sample yields a u series age of 600 15 ka 2 which overlaps with the timing of the warm marine isotope stage mis 15 interglacial the open system model of villemant and feuillet villemant b and feuillet n 2003 dating open systems by the 238u 234u 230th method application to quaternary reef terraces earth and planetary science letters 210 1 2 105 118 and the linear regression or open system isochron is clearly limited for such old samples however the open system model developed by thompson et al thompson w g spiegelman m w goldstein s l and speed r c 2003 an open system model for u series age determinations of fossil corals earth and planetary science letters 210 1 2 365 381 appears to reliably correct for open system effects in roughly half of the corals giving a mis 15 origin for these thus the data provide evidence that the systematic addition of 230th and 234u through recoil is a dominant open system process occurring in the henderson island fossil reef system several coral samples yield significantly older thompson et al open system ages between 650 and 750 ka the uncertainty on these ages typically 30 kyrs is too great for precise assignment but most data overlap with the mis 17 interglacial the reliability of these ages is currently unclear it is shown that separate aliquots of the same coral can yield different thompson model ages therefore there appear to be additional diagenetic mechanisms that create further anomalous excursions in the u series systematics limiting the reliability of the thompson et al open system model

quaternary atoll development new insights from the two dimensional stratigraphic forward modelling of mururoa island central pacific ocean knowledge about the quaternary evolution of mid ocean atolls comes mainly from drilling and field observations carried out on a number of pacific carbonate islands however little is known about the early to mid pleistocene atoll development history especially at margin and foreslope settings using previous field and subsurface data from mururoa atoll and a process based modelling software dionisos a two dimensional forward stratigraphic model of atoll development is proposed for the past 1 8 million years myr observational data from vertical to inclined coring seismic and bathymetric surveys indicate that from approximately 0 45 to 0 40 million years before present ma carbonate deposition at mururoa atoll resulted in a series of mostly prograding reef units the model is first constrained at the base by the shape and topography of the pre quaternary basement a number of sensitivity tests were performed to define the respective influence of variant parameters the best fit development scenario that accounts for the overall geometry and stratigraphic architecture of the quaternary sediment packages is obtained by using the sea level curve by miller et al 2005 uniform subsidence rate of 105 m myr 1 and carbonate production rates gradually increasing from 0 50 to 8 mm yr 1 between 1 80 ma and the present additional controlling parameters include subaerial erosion at a constant rate of 0 25 m kyr wave energy and sediment transport processes the stratigraphic forward model predicts a succession of three distinct types of carbonate systems that have developed since the earliest pleistocene toe of slope systems from 1 80 ma to about 0 80 ma open platform systems from 0 80 ma to 0 50 ma and framework reef systems from about 0 50 ma to the present the development of these different systems is most likely to be controlled by climate and changes in sea level cycles during the low amplitude 41 kyr cycle periods of the earliest pleistocene ambient conditions were not conducive to framework reef growth shallow water carbonate sedimentation was dominantly gravity driven operating along the platform foreslopes only during the mid pleistocene climate transition narrow open platform units have developed at the upper parts of the pre quaternary basement flanks with the onset of the high amplitude 100 kyr sea level modes and climate restoration reef frameworks started to be generated these models from mururoa agree with a number of previous studies suggesting that most of the true framework reefs were not initiated prior to 0 50 ma mururoa atoll is demonstrated to be a robust analogue for providing more realistic interpretations of the development history of pacific atolls further modelling with three dimensional dionisos could generate better predictions by taking into account hydrodynamic and transport parameters more accurately

sr ca and δ18o seasonality in a porites coral from the mis 9 339 303 ka interglacial abstract past changes in the seasonal distribution of insolation across the earth s surface are thought to play a critical role in quaternary climate cycles in this study we use sr ca and 18 o as geochemical proxies in the skeleton of a fossil porites coral to reconstruct the seasonal cycle of sea surface temperature sst at henderson island southeast pacific 24 s 128 w during the marine isotope stage mis 9 interglacial 339 303 ka previously published closed system u series ages provide broad age constraints for the timing of reef growth for this unit on henderson island ranging between 334 and 306 ka we apply published 18 o sst slope relationships to the stacked 18 o annual cycle in the fossil porites and find the amplitude of the seasonal cycle of sst recorded by the mis 9 coral to be 4 1 0 57 c which agrees within error with the modern seasonal cycle of sst 4 1 c sr ca sst slope relationships applied to the fossil porites stacked sr ca annual cycle suggest the amplitude of the seasonal cycle of sst was 4 7 0 75 c exceeding the modern cycle by 15 but within error of the modern value taken together these results suggest the seasonal cycle of sst at henderson island during mis 9 equaled or exceeded the modern amplitude using modern latitudinal relationships between insolation seasonality and sst seasonality we present a new application for sst amplitudes reconstructed from fossil corals that can be used in conjunction with u series ages to provide additional geochronological constraints on the development of open ocean interglacial reefs

pleistocene raised marine terraces of the spanish mediterranean and atlantic coasts records of coastal uplift sea level highstands and climate changes detailed geological mapping morphostratigraphic palaeontological and geochronological uranium series analyses were undertaken on the raised marine terraces and interbedded terrestrial deposits along the spanish peninsular and insular atlantic and mediterranean coasts several sets of pleistocene shallow marine to coastal deposits exposed in a staircase arrangement are interpreted as being emplaced during sea level highstands coeval with interglacials or interstadials correlating with marine oxygen isotopic stages ois 5a 5c 5e 7 9 11 and older up to three highstands have been identified in deposits formed during ois 5e close to the end of ois 5e there is a record of sudden changes in sea surface conditions and climate marked by the disappearance of a major proportion of the warm senegalese fauna switches from oolitic to non oolitic facies and accumulation of boulder beaches dating of the coral cladocora caespitosa found in a layer that also contains strombus bubonius confirms the occurrence of warm fauna in the mediterranean basin during ois 7 as previously suggested by hillaire marcel et al 1986 goy et al 1986a b zazo and goy 1989 also the occurrence of warm faunas in deposits corresponding to an older interglacial probably ois 9 or 11 in the balearic islands suggests similar oceanographic conditions sea surface temperature assuming constant salinity during the last interglacial and at least two interglacials of the middle pleistocene in the western mediterranean a 2002 elsevier science b v all rights reserved

a global compilation of coral sea level benchmarks implications and new challenges i present a quality controlled compilation of sea level data from u th dated corals encompassing 30 studies of 13 locations around the world the compilation contains relative sea level rsl data from each location based on both conventional and open system u th ages i have applied a commonly used age quality control criterion based on the initial 234u 238u activity ratios of corals in order to select reliable ages and to reconstruct sea level histories for the last 150 000 yr this analysis reveals scatter of rsl estimates among coeval coral benchmarks both within individual locations and between locations particularly during marine isotope stage mis 5a and the glacial inception following the last interglacial the character of data scatter during these time intervals imply that uncertainties still exist regarding tectonics glacio isostacy u series dating and or coral position to elucidate robust underlying patterns with confidence limits i performed a monte carlo style statistical analysis of the compiled coral data considering appropriate age and sea level uncertainties by its nature such an analysis has the tendency to smooth obscure millennial scale and finer details that may be important in individual datasets and favour the major underlying patterns that are supported by all datasets this statistical analysis is thus functional to illustrate major trends that are statistically robust what we know trends that are suggested but still are supported by few data what we might know subject to addition of more supporting data and improved corrections and which patterns data are clear outliers unlikely to be realistic given the rest of the global data and possibly needing further adjustments prior to the last glacial maximum and with the possible exception of the 130 120 ka period available coral data generally have insufficient temporal resolution and unexplained scatter which hinders identification of a well defined pattern with usefully narrow confidence limits this analysis thus provides a framework that objectively identifies critical targets for new data collection improved corrections and integration of coral data with independent stratigraphically continuous methods of sea level reconstruction

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

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

u th dating of marine isotope stage 7 in bahamas slope sediments in order to understand the driving forces for pleistocene climate change more fully we need to compare the timing of climate events with their possible forcing in contrast to the last interglacial marine isotope stage mis 5 the timing of the penultimate interglacial mis 7 is poorly constrained this study constrains its timing and structure by precise u th dating of high resolution n 18 o records from aragonite rich bahamian slope sediments of odp leg 166 sites 1008 and 1009 the major glacial interglacial cycles in n 18 o are distinct within these cores and some mis 7 substages can be identified these sediments are well suited for u th dating because they have uranium concentrations of up to 12 ppm and very low initial 230 th contributions with most samples showing 230 th 232 th activity ratio of s 75 u and th concentrations and isotope ratios were measured by thermal ionisation mass spectrometry and multiple collector inductively coupled plasma mass spectrometry with the latter providing dramatically better precision twenty nine of the 41 samples measured have a n 234 u value close to modern seawater suggesting that they have experienced little diagenesis ages from 27 of the 41 samples were deemed reliable on the basis of both their u and their th isotope ratios ages generally increase with depth although we see a repeated section of stratigraphy in one core extrapolation of constant sedimentation rate through each substage suggests that the peak of mis 7e lasted from v237 to 228 ka and that 7c began at 215 ka this timing is consistent with existing low precision radiometric dates from speleothem deposits the beginning of both these substages appears to be slightly later than in orbitally tuned timescales the end of mis 7 is complex but also appears to be somewhat later than is suggested by orbitally tuned timescales although this event is not particularly well defined in these cores fl 2002 elsevier science b v all rights reserved

millennial scale variability to 735 ka high resolution climate records from santa barbara basin ca 1 determining the ultimate cause and effect of millennial scale climate variability remains an outstanding problem in paleoceanography partly due to the lack of high resolution records predating the last glaciation recent cores from santa barbara basin provide 2500 5700 year windows of climate with 10 50 year resolution ages for three cores determined by seismic stratigraphic correlation oxygen isotope stratigraphy and biostratigraphy date to 293 ka mis 8 450 ka mis 12 and 735 ka mis 18 these records sample the late pleistocene during which the 100 kyr cycle strengthened and the magnitude of glacial interglacial cyclicity increased thus these records provide a test of the dependence of millennial scale behavior on variations in glacial interglacial cyclicity the stable isotopic 18o composition of planktonic foraminifera shows millennial scale variability in all three intervals with similar characteristics duration cyclicity to those previously documented during mis 3 at this site stadial g bulloides 18o values are 2 75 1 75 average 2 25 and interstadial values are 1 75 0 5 average 1 with rapid decadal scale interstadial and stadial initiations of 1 2 as in mis 3 interstadials lasted 250 1600 years and occurred every 650 1900 years stadial paleotemperatures were 3 5 9 5 c and interstadial paleotemperatures were 7 5 13 c upwelling evidenced by planktonic foraminiferal assemblages and 13c increased during interstadials similar to mis 3 high productivity during some stadials was reminiscent of the last glacial maximum this study builds upon previous records in showing that millennial scale shifts were an inherent feature of northern hemisphere glacial climates since 735 ka and they remained remarkably constant in the details of their amplitude cyclicity and temperature variability

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

the timing of sea level high stands during marine isotope stages 7 5 and 9 constraints from the uranium series dating of fossil corals from henderson island direct dating of fossil coral reefs using the u series chronometer provides an important independent test of the milankovitch orbital forcing theory of climate change however well dated fossil corals pre dating the last interglacial period 130 thousand years ago ka are scarce due to 1 a lack of sampling localities 2 insufficient analytical precision in u series dating methods and 3 diagenesis which acts to violate the assumption of closed system u series isotopic decay in fossil corals here we present 50 new high precision u series age determinations for fossil corals from henderson island an emergent coral atoll in the central south pacific u series age determinations associated with the marine isotope stage mis 9 interglacial and mis 7 5 interstadial periods are reported the fossil corals show relatively little open system u series behaviour in comparison to other localities with fossil coral reefs formed prior to the last glacial cycle however open system u series behaviour is still evident in most of the dated corals in particular percent level shifts in the 230th 238u act composition are observed leading to conventional u series ages that are significantly younger or older than the true sample age this open system u series behaviour is not accounted for by any of the open system u series models indicating that new models should be derived the new u series ages reported here support and extend earlier findings reported in stirling et al 2001 providing evidence of prolific coral reef development on henderson island at not vert similar320 ka most likely correlated with mis 9 3 and subsequent reef development at not vert similar307 ka during mis 9 1 while relative sea level was potentially not vert similar20 m lower than during mis 9 3 the u series ages for additional well preserved fossil corals are suggestive of minor reef development on henderson island during mis 7 5 245 230 ka at 240 3 0 8 and 234 7 1 3 ka all u series observations are consistent with the milankovitch theory of climate change in terms of the timing of onset and termination of the dated interglacial and interstadial periods the best preserved samples also suggest that the oceanic 234u 238u during mis 9 and mis 7 5 was within five permil of the modern open ocean composition

terminations and their correlation with solar insolation in the northern hemisphere a record from a loess section in northwest china a high resolution loess section in northwest china is analyzed for the major climate terminations and their correlation with solar insolation over the past 0 8 ma based on age controls and a grain size age model proposed by porter and an porter s c an z s 1995 correlation between climate events in the north atlantic and china during the last glaciation nature 375 305 308 a timescale for the shagou loess section is constructed which is independent of orbital tuned results the timescale is similar to other loess sections and the mid point ages of the boundary between a paleosol and its underlying loess layer are very close to that of terminations recorded in the marine record shagou section records indicate that grain size changed sharply during the termination process terminations occurred at the time of the maximum or increase of july radiation in the northern hemisphere at high latitudes suggesting that insolation might be a factor affecting terminations in the chinese loess this result supports the milankovitch hypothesis however variations in the amplitude of the insolation and grain size records are not proportionally matched so that the mechanism remains unsolved

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

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

centennial scale cycles in middle holocene sea level along the southeastern swedish baltic coast submerged sea grasses and stoneworts growing in the immediate nearshore of the baltic sea are sensitive indicators of sea level the alternating changes in concentrations of sea grass and stonewort macrofossils obtained from an ancient lagoon of the baltic sea are ascribed to middle holocene sea level fluctuations along the southeastern swedish coast abundances of stonewort and sea grass macrofossils between 7500 and 6000 cal calibrated yr b p were lower and less variable indicating high and relatively stable sea level low frequency fluctuations of sea level with a 1470 yr period during this time may have been forced by tidal action in the millennial band after 6000 cal yr b p sea level was lower and exhibited strong fluctuations at centennial time scales as evident in the stonewort and sea grass macrofossil records such a high frequency oscillatory mode of sea level may have been regulated by centennial scale solar activities or tidal actions or both the modest variation in solar irradiance is unlikely to have resulted in large scale oscillations of sea level by directly changing the steric component instead it governed sea level fluctuations by changing the regional storminess through a north atlantic oscillation nao like system storms embedded in the nao induced southwesterly winds played a major role in the centennial scale fluctuations of the baltic sea level by pushing saltwater from the north sea into the baltic basin less

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

quaternary marine terraces on sal island cape verde archipelago abstract the quaternary sedimentary record of sal island includes marine and related aeolian and alluvial fan deposits the substratum of the island is volcanic with ages between 25 and 0 6 ma quaternary marine units generally occur as raised marine terraces forming a broad staircase between elevations of 55 60 m and present sea level terraces include a basal conglomerate overlaid by calcarenite both host corals algae and molluscs a chronostratigraphic framework for the middle pleistocene to holocene units has been generated based on a geomorphologic map of the quaternary landforms and associated deposits and morphosedimentary analysis with support of laboratory dating u series by tims in corals 14 c analyses palaeomagnetic measurements and k ar ages from other literature u series dating of corals from marine terraces provides benchmarks for the last interglacial oxygen isotope substage 5e and holocene deposits the present elevation of the marine terraces and their staircase arrangement suggest a change in vertical movement trend around 330 ka from an uplift to either subsidence or stabilization

u series evidence for widespread reef development in shark bay during the last interglacial field observations and u series ages reveal that shark bay western australia wa has been inundated by the sea on at least three occasions during the late pleistocene holocene resulting in a succession of marine deposits around the bay the exact age of these deposits has until now been problematic due to a lack of reliable and accurate age data this study reports 16 new u series coral dates from emergent reef deposits around shark bay and point to an extended period of coral reef development during the peak of the last interglacial marine isotope stage mis 5e this is attributed to enhancement of marine circulation within the reaches and basins a result of higher sea levels and an absence of major sill and bank structures stromatolites are absent from the geological record within shark bay until the late holocene suggesting that sea levels and marine sedimentary processes that have operated during the present sea level highstand are unique to this period there is little direct evidence of fossil reef development occurring during interglacials of the middle late pleistocene mis 9 11

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

reconstruction of quaternary temperature fields by dynamically consistent smoothing conventional methods of palaeoclimate reconstruction provide estimates of climatic parameters using proxy data which have originated from individual sites these reconstructions yield information on the local environment but only limited information on spatial scales that are required for model data intercomparisons we present here a new approach that connects these different scales by an upscaling of the local palaeoinformation together with a dynamically consistent spatial smoothing a probabilistic data based method for local reconstructions is combined with a dynamic constraint on the reconstructed climate parameter which stabilises the reconstruction on the target scale the variational analysis leads to climatological fields being optimised with respect to the proxy data and to the prescribed dynamics in a statistically consistent way this method allows a probabilistic approach of quality control of the palaeodata in terms of their spatial consistency and homogeneity and for an estimation of reconstruction errors the method was applied to palaeobotanical data to reconstruct near surface temperature fields constrained by simple linear dynamics an approximate approach was used to estimate the magnitude of reconstruction errors in terms of standard deviations reconstructed january and july mean temperature of the early eemian 125 000 years bp have errors with a median value of about 1 8 c in january and about 1 1 c in july reconstructions across europe show positive temperature anomalies for scandinavia and near the east coast of the baltic sea in contrast early eemian temperatures were apparently quite similar to those found today in central europe as no drastic differences were reconstructed between the eemian and modern 1961 1990 climate this implies somewhat stronger temperature gradients in the eemian than are observed today

dating open systems by the 238 u 234 u 230 th method application to quaternary reef terraces abstract the sedimentation conditions and diagenetic processes of biogenic and inorganic carbonates are such that the assumptions of a closed system evolution and the absence of initial th invoked in classical 238 u 234 u 230 th dating methods are very often not fulfilled for such material this problem is of interest for all studies requiring accurate dating of corals or aragonite rich sediments as in palaeoclimatology or neotectonics extending the approach of henderson and slowey nature 404 2000 61 66 we propose a consistent model that takes into account possible initial 230 th excess and where continuous selective redistribution gain or loss of 234 u 234 th and 230 th is controlled by recoil processes this model applied to quaternary marine terraces in barbados marie galante lesser antilles arc and pacific islands is able to explain the large scatter in isotopic compositions observed in the series of cogenetic corals or sediments we show that recoil processes generally tend to increase the 234 u 238 u and 230 th 234 u ratios with time leading to an overestimation of the apparent ages calculated using classical methods on the basis of simple assumptions identical marine initial 234 u 238 u 0 and 230 th 232 th 0 ratios we propose a method for calculating a best estimate of the age of cogenetic series our model offers an alternative way to date old reef terraces where corals are almost systematically altered and where classical dating methods do not apply it may also explain the apparent variations of the 234 u 238 u seawater initial ratio estimated from corals formed in the last 300 ka and the apparent uncoupling between sea level highstands and high latitude northern hemisphere summer insolation our set of equations can be applied to all weathering processes where the mobility of u series isotopes is controlled by recoil

history of the greenland ice sheet paleoclimatic insights abstract paleoclimatic records show that the greenland ice sheet consistently has lost mass in response to warming and grown in response to cooling such changes have occurred even at times of slow or zero sea level change so changing sea level cannot have been the cause of at least some of the ice sheet changes in contrast there are no documented major ice sheet changes that occurred independent of temperature changes moreover snowfall has increased when the climate warmed but the ice sheet lost mass nonetheless increased accumulation in the ice sheet s center has not been sufficient to counteract increased melting and flow near the edges most documented forcings and ice sheet responses spanned periods of several thousand years but limited data also show rapid response to rapid forcings in particular regions near the ice margin have responded within decades however major changes of central regions of the ice sheet are thought to require centuries to millennia the paleoclimatic record does not yet strongly constrain how rapidly a major shrinkage or nearly complete loss of the ice sheet could occur the evidence suggests nearly total ice sheet loss may result from warming of more than a few degrees above mean 20th century values but this threshold is poorly defined perhaps as little as 2 c or more than 7 c paleoclimatic records are sufficiently sketchy that the ice sheet may have grown temporarily in response to warming or changes may have been induced by factors other than temperature without having been recorded

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

errors in hypocenter location picking model and magnitude dependence abstract the location procedures of seismic events are influenced by two major classes of errors the error in picking individual seismic phases and modeling error due to the departure of the real earth from the reference model used in the location both classes of error influence the estimate of location and it is difficult to separate them the role of picking errors can be assessed by a nonlinear analysis using a monte carlo procedure arrivals times are perturbed with random numbers drawn from a normal distribution and the event is relocated using these perturbed arrival times by repeating the procedure many times a cluster of locations is obtained which can be used to investigate the effects of picking errors on the hypocenter this analysis is insensitive to velocity model errors as these are fixed for a given combination of stations and phases some care must be exercised when analysing multidimensional distributions in two dimensional slices because of a projection effect the modeling error due to the influence of lateral heterogeneity in the earth is examined by comparing the locations of the same event using different combinations of phases and network geometries which reinforces the need to use arrivals other than p for accurate depth resolution the sensitivity of p arrivals to changes in depth are swamped by model errors and inclusion of depth sensitive phases such as pp is highly recommended the effect of picking errors on location is found to be much smaller than the mislocation caused by neglecting lateral heterogeneity when only p arrivals are used consequently the monte carlo analysis which is primarily aimed at picking errors only is most appropriate when multiple phases have been used to more accurately constrain the hypocenter especially for the depth component altering the type of phase data used in the location plays a similar role in changing the network geometry in that both are mechanisms that influence the nature of the constraint on the hypocenter by relocating events with network geometries corresponding to the different magnitudes it is found that the location of the event can be affected significantly by the magnitude and when using robust statistics to describe earthquake residuals the mislocation can occur in a systematic manner the effect is marked in regions with significant lateral variations in seismic velocities for example low magnitude events in the flores sea are found to be dragged toward australia as a result of the fast paths to australian stations relative to the iasp 91 reference velocity model

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

sediment transport time measured with u series isotopes results from odp north atlantic drift site 984 abstract high precision uranium isotope measurements of marine clastic sediments are used to measure the transport and storage time of sediment from source to site of deposition the approach is demonstrated on fine grained late pleistocene deep sea sediments from ocean drilling program site 984a on the bjorn drift in the north atlantic the sediments are siliciclastic with up to 30 carbonate and dated by 18o of benthic foraminifera nd and sr isotopes indicate that provenance has oscillated between a proximal source during the last three interglacial periods volcanic rocks from iceland and a distal continental source during glacial periods an unexpected finding is that the 234u 238u ratios of the silicate portion of the sediment isolated by leaching with hydrochloric acid are significantly less than the secular equilibrium value and show large and systematic variations that are correlated with glacial cycles and sediment provenance the 234u depletions are inferred to be due to recoil loss of 234th and are used to calculate comminution ages of the sediment the time elapsed between the generation of the small 50 m sediment grains in the source areas by comminution of bedrock and the time of deposition on the seafloor transport times the difference between comminution ages and depositional ages vary from less than 10 ky to about 300 to 400 ky for the site 984a sediments long transport times may reflect prior storage in soils on continental shelves or elsewhere on the seafloor transport time may also be a measure of bottom current strength during the most recent interglacial periods the detritus from distal continental sources is diluted with sediment from iceland that is rapidly transported to the site of deposition the comminution age approach could be used to date quaternary non marine sediments soils and atmospheric dust and may be enhanced by concomitant measurement of 226ra 230th 230th 234u and cosmogenic nuclides

reply to comment on errors in hypocenter location picking model and magnitude dependence by c lomnitz the comment by lomnitz 1995 on our article billings et al 1994a points out that there are a number of potential causes of earthquake mislocations that are not dealt with in our treatment we entirely agree with him our article as is suggested by the title deals with just three potential sources of earthquake location error it was never intended nor did we claim that it was an exhaustive analysis of hypocentral mislocations in our view the sources of mislocation outlined by lomnitz 1995 are all important in response to the specific comments and suggestions made by lomnitz 1995 we have only two points to add first the dependence of earthquake location on the station distribution is dealt with in our paper under the heading magnitude dependence billings et al 1994b pointed out that events with different magnitudes from the same source region will often be detected by a different number and distribution of seismic stations around the world each event is therefore located with a different configuration of stations and so the dependence of the mislocation on the distribution of receivers will lead to a dependence on the magnitude of the event in our article we illustrated this with an example from the flores sea but it is equally applicable in other parts of the world therefore the dependence of mislocation on magnitude and station distribution are essentially the same second lomnitz 1995 suggests that earthquake location procedures might perform better if they decouple the estimation of the focal depth parameter from the epicentral parameters we would like to point out that this is one of the features of the genetic algorithm hypocenter location procedure described by billings et al 1994a they found it was possible to improve performance and stability of the location algorithm by exploiting two types of decoupling the first between spatial and temporal parameters and the second between depth and epicentral parameters we would like to thank dr lomnitz for the opportunity to clarify these issues

foredeep tectonics and carbonate platform dynamics in the huon gulf papua new guinea hawaii mr1 side scan sonar and six channel seismic reflection data reveal a history of carbonate platform growth drowning and back stepping in the huon gulf papua new guinea this is one of the few modern sites where active carbonate platform development and foredeep subsidence are linked 230 th methods date aragonitic shallow water corals recovered from a modern depth of 2000 m at 348 10 ka this documents rapid subsidence of the huon gulf in response to the encroaching finisterre mountains at an average rate of 5 7 mm yr for the past 348 k y the highest subsidence rate reported from any foredeep setting carbonate deposition has moved toward the foreland at an average rate of 110 mm yr over the same period comparisons of the measured age with sea level history derived from the oxygen isotope record suggest that the reefs may have formed during sea level lowstands and drowned during rapid rates of sea level rise

evidence for the timing and duration of the last interglacial period from high precision uranium series ages of corals on tectonically stable coastlines the last interglacial period has a timing and duration that can be estimated from u series dating of emergent coral bearing deposits on tectonically stable coastlines high precision dating from bermuda the bahamas hawaii and australia suggests that the last interglacial period had a sea level at least as high as present from 128 000 to 116 000 yr b p sea level reached a near present level more quickly after the close of the penultimate glacial period than at the close of the last glacial period and the duration of high sea level is longer than that implied by the deep sea record c 2002 university of washington

on the long lasting sequences of coral reef terraces from se sulawesi indonesia distribution formation and global significance many islands of the eastern indonesian archipelago exhibit late cenozoic sequences of coral reef terraces in se sulawesi on the tukang besi and buton archipelagos we identified 23 islands bearing such sequences remote sensing imagery and field mapping combined to u th and 14c dating enable to establish a chronologic framework of the reef terrace sequences from wangi wangi buton as well as on the neighbouring smaller islands of ular siumpu and kadatua we identified the terraces from the last interglacial maximum mis 5e at elevations lower than 20 m except on w kadatua where it is raised at 34 5 m such elevations yield low to moderate upper pleistocene uplift rates 0 3 mm yr 1 on se buton island a sequence culminates at 650 m and includes at least 40 undated strandlines next to this exceptional sequence on the sampolawa peninsula 18 strandlines culminate at 430 m dated samples at the base of this sequence 40 m yield mean middle pleistocene uplift rates of 0 14 0 09 mm yr 1 extrapolation of these uplift rates compared to the geological setting suggests that the sequences of the sampolawa peninsula provide a record of sea level high stands for the last 3 8 0 6 ma the sequences on se buton island therefore constitute the best preserved long lasting geomorphic record of plio quaternary sea level stands worldwide

early diagenesis impact on precise u series dating of deep sea corals example of a 100 200 year old lophelia pertusa sample from the northeast atlantic deep sea coral has proved useful for paleoceanographic reconstructions and for documenting 14 c ages of water masses using 230 th ages however for precise and accurate u series dating further information on coral age structure growth rate and diagenetic evolution is still needed to document such processes we used u th 226 ra systematics in a 40 cm diameter lophelia pertusa specimen collected in 1912 from the eastern atlantic sea of the hebrides external parts of the specimen are thought to have been alive when collected whereas more internal parts were likely dead the live collected and dead parts of the skeleton were sampled and analyzed for their 230 th 232 th 234 u 238 u 226 ra and ba contents by thermal ionization and multicollector inductively coupled plasma mass spectrometry 230 th 234 u ratios in the most recent parts yielded ages of 86 6 a and 92 9 a in agreement with the date of recovery the older parts yielded 230 th ages ranging from 169 15 to 211 10 a n 5 but had a 31 higher u content than more recent parts of the skeleton this raises concerns about the possibility of secondary diagenetic u uptake although an environmentally controlled u ca shift between coral growth stages cannot be ruled out 226 ra ba measurements were made and model 226 ra ba ages averaging 250 12 yr were calculated for the older part assuming a constant initial 226 ra ba ratio in bottom waters these ages are slightly older than 230 th ages suggesting either that 226 ra ba ratios of ambient seawater changed over time or that a diagenetic phenomenon have affected the u series system or both scanning electron microscope observations revealed bioerosion and secondary biomineralization in the older part of the coral skeleton supporting the hypothesis that diagenetic processes may have influenced the ages obtained by the u series toolbox modeled u series ages for such an open system are discussed however a comparison between 14 c and 230 th ages performed on both pristine and bioeroded parts of the coral gives coherent values ca 450 a for the preindustrial 14 c reservoir age of north atlantic waters it remains to be determined however whether diagenesis occurs rapidly over a short period of time or whether it continues for longer periods in the latter case diagenetic processes would hamper paleoceanographic interpretations as well as the precise calculation of 14 c ages of deep water masses based on comparative u th and 14 c chronologies copyright 2005 elsevier ltd

coral indicators of past sea level change a global repository of u series dated benchmarks fossil corals provide valuable data for reconstructing past sea levels as they are often well preserved in the fossil record and can be dated with u series methods here we present a global and internally consistent database of usingle bondth dated fossil coral sea level indicators including full consideration of all known associated uncertainties both vertical and chronological we include carefully determined taxon specific depth distributions rather than blanket depth uncertainty terms as used in most previous work this is based on a synthesis of extensive modern ecological information on depth ranges these ranges are found to be spatially variable between ocean basins between regions and on sub regional scales because depth itself is not limiting instead depth distributions arise from complex physical chemical and biological interactions with coral reef growth distribution and composition one of the main causes for recognition of the greater depth variability of coral taxa has been the routine inclusion of deep diving and rov surveys in coral ecological studies over the past few decades which has broken through the shallow water bias of early surveys by adding frequent observations on deeper occurrences although more are needed it is also clear from our assessment that coral habitat depth distributions must be determined on the species level to reduce uncertainties in reconstructions of past sea levels and that application to sea level studies then requires these studies also to identify fossil corals to the species level samples identified only to the genus level give rise to wide uncertainties in habitat depth and hence sea level our database contains extensive metadata to assist evaluations of dating quality as well as geomorphic and stratigraphic metadata we demonstrate with examples how such metadata can help to evaluate sea level reconstructions for example by identifying outlier points one example discusses the last interglacial lig where we use the available data with their uncertainties to assess probabilistically the time at which local sea levels exceed that of the present which yields a mean age of 124 6 ka with 95 probability bounds at 118 5 and 129 5 ka we conclude with identification of key outstanding issues relating to i current incomplete understanding of tectonic setting including the current lack of independent verification of uplift subsidence rates and reliance of somewhat unsatisfactory and circular use of the elevation of last interglacial deposits ii the depth distributions of coral taxa and iii the complete documentation of stratigraphic geomorphological and other contextual information with suggestions for strategies to address these issues

pleistocene sea levels and tectonic uplift based on dating of corals from sumba island indonesia we collected and dated fossil corals from the uplifted reef tracts of sumba island mass spectrometry tims and ams was used to obtain reliable and precise radiochronological results it is possible to identify outcrops corresponding to major sea level high stands isotope stage 1 starting at 7 1 kyr bp 5a c a 86 kyr bp 5c c a 105 kyr bp 5e between 119 and 132 kyr bp and 9 c a 305 kyr bp the radiochronological data are thus broadly consistent with the timing of sea level fluctuations predicted by the astronomical theory of paleoclimates comparison with similar data from other terrace sequences and from benthic 18o records indicates that the average tectonic uplift rate at cape laundi sumba is on the order of 0 2 0 5m kyr the lowest values 0 3m kyr lead to the build up of polycyclic topographic terraces in which it is possible to find corals grown during different interstadial or even interglacial times

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

open system modelling for u series and esr dating of teeth abstract the study of the constituents of teeth dentine and enamel by a combination of esr and u series techniques offer unique constraints on the history of uranium migration into these materials our results imply that it is inappropriate to assume a simplified u uptake model for neither the components of a single tooth nor for the faunal remains of a given site however the combination of both methods may provide a new technique for establishing reliable chronologies for archaeological quaternary sites of up to several hundred thousand years

the sea level conundrum case studies from palaeo archives uncertainties in sea level projections for the 21st century have focused ice sheet modelling efforts to include the processes that are thought to be contributing to the recently observed rapid changes at ice sheet margins this effort is still in its infancy however leaving us unable to make reliable predictions of ice sheet responses to a warming climate if such glacier accelerations were to increase in size and frequency the geological record however has long identified examples of nonlinear ice sheet response to climate forcing shackleton nj opdyke nd 1973 oxygen isotope and paleomagnetic stratigraphy of equatorial pacific core v28 239 late pliocene to latest pleistocene geological society of america memoirs145 449 464 fairbanks rg 1989 a 17 000 year glacio eustatic sea level record influence of glacial melting rates on the younger dryas event and deep ocean circulation nature342 637 642 bard e hamelin b arnold m montaggioni l cabioch g faure g rougerie f 1996 sea level record from tahiti corals and the timing of deglacial meltwater discharge nature382 241 244 thus suggesting an alternative strategy for constraining the rate and magnitude of sea level change that we might expect by the end of this century copyright 2009 john wiley sons ltd

coral reefs and sea level change abstract coral reefs provide significant evidence for former sea level positions because of their geological preservation and suitability for dating interpretation of this evidence presumes an understanding of reef geomorphology modern reef organism distributions and environmental factors influencing them fossil reef terraces formed during the last interglacial marine oxygen isotope mis substage 5e 128 116 ka are prevalent on many tropical shorelines and there has been ongoing debate as to the height reached by sea level during that highstand observations from numerous last interglacial sites suggest that sea level was at least 3 m above present sea level implying less extensive icesheets than at present an elevation of 6 m has commonly been adopted when correcting tectonically active sites for uplift recent compilations suggest elevations up to 8 9 m but incorporate few observations from reefs where the last interglacial is found below sea level oscillation of sea level during mis 5e has been interpreted from several sites with recent studies inferring rapid rise of several metres at the end of the interglacial these interpretations are at the limits to the precision with which corals can currently be dated and their palaeo water depths inferred it is not surprising that constraining last interglacial sea level changes within uncertainties of less than 1 2 m remains controversial considering sea level variations recognised between reef sites in the holocene and observed geographical variation in isostatic or flexural adjustments fossil coral reefs on uplifting margins also provide clear evidence for mis substages 5c and 5a and those on huon peninsula indicate fluctuations related to heinrich events mis 3 interpretations show considerable variability between sites with still greater uncertainties about sea level timing and elevation during previous interglacials future study of extensive sequences of fossil reefs preserved on rapidly subsiding margins could address these uncertainties submerged reefs have already yielded important information about sea level rise during the last deglaciation coring around barbados and tahiti as well as on the huon peninsula has produced a broadly consistent picture of ice melt reflecting eustatic change since the last glacial maximum these studies have shown the sensitivity of reefs to rapid sea level rise associated with meltwater pulses with some reefs drowning while others back stepped integrated ocean drilling program iodp expeditions to tahiti and recently the great barrier reef extended these records but details of timing nature and impact of deglacial meltwater pulses remain elusive studies of holocene reefs have indicated different growth strategies some kept up with sea level while others caught up when sea level decelerated holocene sea level appears to have experienced a gradual rise up to present across the caribbean providing accommodation space for reefs to accrete vertically whereas in the indo pacific sea level has been near its present level since 7 ka with many reef flats emergent following a slight fall of sea level caused by ocean siphoning microatolls on reef flats provide perhaps the clearest evidence of past sea level position but in their absence novel biological or other sea level indicators are required to better constrain palaeo water depths there is an urgent need for further research from additional key reef locations not only to decipher processes driving past sea level change and its geographical variability but also to better understand how coral reefs will respond in the context of future sea level rise

accelerated pleistocene coral extinctions in the caribbean basin shown by uranium lead u pb dating ages of corals and shallow marine sequences define rates of marine invertebrate evolution tectonic uplift and paleoclimate change yet accurate ages are difficult to obtain prior to the late pleistocene we report a new approach for combining uranium lead u pb and uranium series dating for middle pleistocene corals from the caribbean side of costa rica two corals have 230 th 238 u in secular equilibrium small excesses in 234 u and 206 pb 238 u ages of 1 02 0 07 ma and 1 288 0 034 ma the latter coral age dates a recognized geomagnetic event to ca 1 3 ma a time at which no polarity events had been identified the new ages also show that the major coral extinction in the caribbean basin occurred shortly after 1 0 0 9 ma much more recently than previously thought this coral extinction now coincides with the global change at 1 0 0 8 ma to the current pattern of glacial interglacial cycles and amplified changes in sea level these factors may have provided a new strong environmental mechanism for rapid habitat modification and coral extinction

two middle pleistocene warm stages in the terrace deposits of the apulia region southern italy abstract we studied two middle pleistocene terraced deposits exposed along the trani cliff and at coppa nevigata in the apulia region southern italy in particular our study focused on stromatolitic units that are present at two sites at the trani cliff unit i consists of cemented whitish fine grained massive or bedded limestone the limestone grades upwards into massive porous bioconstructed calcareous bodies composed of in situ charophyta stems and or stromatolites the uppermost part of the unit is composed of whitish calcarenite calcisiltite layers with characeae the interpreted sedimentary environment for this unit is a hypersaline brackish lagoon at coppa nevigata the nvi unit is composed of tawny or yellow ochre sand with rare polygenic centimetric pebbles the sand grades upwards into light yellow and ochre sandy clayey silt or clay some layers are cemented and form marly limestones which contains columnar stromatolites the uppermost part of the unit consists of yellow ochre or tawny marly limestones and marls that are rich in external moulds of abra sp and cerastoderma glaucum the interpreted sedimentary environment for this unit is a brackish lagoon unit i and the nvi unit have been dated to mis 9 and mis 11 respectively by applying the amino acid racemisation aar method to ostracod shells the stromatolites of the nvi unit are ascribable to sh type whereas those of unit i are ascribable to sh and llh types and to colloform type in particular the stromatolites at the trani cliff are similar in shape and sedimentary environment to the modern stromatolites in shark bay australia the water temperature and salinity conditions under which the current stromatolites live indicate that tropical subtropical conditions were present in the mediterranean sea during mis 11 and mis 9 our reconstructions suggest that 1 during mis 11 the sea surface temperatures ssts were consistent with literature data that indicate ssts 3 c higher than the current ones 2 during mis 9 the lagoon in which unit i formed had a mean water temperature of the coldest month at least 10 12 c higher than that in modern southern adriatic and at least 3 4 c higher than that in some modern north african lagoons therefore our study supports the hypothesis that the mediterranean sea experienced tropical subtropical conditions during mis 9 that were similar to those of mis 11

carbonate sedimentation on subtropical shelves around lord howe island and balls pyramid southwest pacific abstract lord howe island and balls pyramid are mid oceanic basaltic islands 20 km apart in the tasman sea subaerial carbonates dating back at least 350 ka and a holocene fringing reef occur on lord howe island no reefs or subaerial carbonate deposits occur on balls pyramid both islands sit near the centre of wide shelves that are on average 40 50 m deep with a distinct break of slope between 70 and 100 m depth the lord howe shelf is characterised by a discontinuous drowned ridge which rises to 30 m depth and is located between the mid shelf and shelf edge it is composed of limestone and is interpreted as a fossil reef being veneered by holocene coralline algae early to middle holocene branching coral gravel is found in the lee of the fossil reef indicating limited give up reef growth during the postglacial transgression the surface sediments across the shelf are calcareous except in close proximity to the island where volcanic content is significant coralline algae represent the dominant grain type with minor amounts of coral bryozoans halimeda and foraminifera are common however they are not volumetrically important rhodoliths and molluscs occur near the shelf edge and appear to have accumulated at times of lower sea level these subtropical shelves are mid oceanic examples of the transition between tropical and temperate carbonate sedimentation they indicate the potential for carbonate production on broad planated shelves outside reef forming seas