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

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

searching for eustasy in deglacial sea level histories abstract perturbations to the earth s gravity field and solid surface associated with glacial isostatic adjustment gia cause the total observable sea level change to depart from the eustatic curve which is defined as a spatially uniform height shift of the ocean surface to accommodate any mass gained lost from grounded ice in this study we apply a state of the art model of gia induced sea level change to quantify the magnitude and spatial form of this departure at the global scale for a range of model parameters with an aim to identify regions that are well suited to obtain accurate and precise estimates of eustatic sea level and therefore past grounded ice volume in general our results indicate that eustatic sea level is not a directly measurable quantity and so must be estimated by subtracting a model derived estimate of non eustatic contributions from observations in this regard we use our results to isolate regions where this procedure can be applied with optimal accuracy and precision that is where 1 the gia predictions are relatively insensitive to plausible ranges in input parameters and 2 where the non eustatic contribution is small i e the predicted sea level closely approximates the eustatic value we present maps that can be employed by the field community to identify areas where sea level reconstructions would be well suited to arrive at robust estimates of eustatic sea level note that sea level changes associated with tectonic motion and changes in ocean water temperature salinity which also lead to departures from eustasy are not considered in this analysis

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

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

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

reconciliation of sea level observations in the western north atlantic during the last glacial cycle abstract a south to north gradient of increasing marine isotope substage mis 5a 80 ka bp sea level has been recorded across the caribbean and surrounding region relative to present mis 5a sea levels range from 19 m to more than 3 m between barbados haiti the bahamas florida bermuda and the us atlantic coast in contrast no gradient in sea level is observed for the last interglacial period mis 5e 128 118 ka bp at tectonically stable localities in the same region with deposits generally lying several metres above present we demonstrate here that these controversial observations are reconciled by taking into account the isostatic response of the earth to glacial loading and unloading a fundamental effect that is commonly overlooked in the interpretation of sea level observations from different locations to define a global sea level curve furthermore the observed gradient can be used to place constraints on earth rheology and is an important indicator of the behaviour of the north american ice sheets during the last glacial cycle

seismic hazard of the enriquillo plantain garden fault in haiti inferred from palaeoseismology the enriquillo plantain garden fault zone is the primary plate bounding fault system in haiti and was initially thought to be responsible for the 2010 earthquake palaeoseismic analyses of the fault system indicate that it ruptured during a large earthquake in either 1750 or 1770 but did not rupture during the 2010 earthquake the enriquillo plantain garden fault zone is recognized as one of the primary plate bounding fault systems in haiti1 2 the strike slip fault runs adjacent to the city of port au prince and was initially thought to be the source of the 12 january 2010 mw 7 0 earthquake haiti experienced significant earthquakes in 1751 and 1770 refs 3 4 5 but the role of the enriquillo plantain garden fault zone in these earthquakes is poorly known we use satellite imagery aerial photography light detection and ranging lidar and field investigations to document quaternary activity on the enriquillo plantain garden fault we report late quaternary left lateral offsets of up to 160 m and a set of small offsets ranging from 1 3 to 3 3 m that we associate with one of the eighteenth century earthquakes the size of the small offsets implies that the historical earthquake was larger than mw 7 0 but probably smaller than mw 7 6 we found no significant surface rupture associated with the 2010 earthquake the lack of surface rupture coupled with other seismologic geologic and geodetic observations6 7 suggests that little if any accumulated strain was released on the enriquillo plantain garden fault in the 2010 earthquake these results confirm that the enriquillo plantain garden fault remains a significant seismic hazard

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

a 20 m middle pleistocene sea level highstand bermuda and the bahamas due to partial collapse of antarctic ice marine deposits at 20 3 m on the tectonically stable coastlines of bermuda and the bahamas support the hypothesis of a partial collapse of the antarctic ice sheet during the middle pleistocene beach sediments fill a sea cave at 22 m in bermuda and horizontal fenestrae filled beds crop out on platforms at two sites as high as 21 m in eleuthera bahamas carbonate beach sands are bound by an early generation of isopachous fibrous cement that is characteristic of a phreatic marine environment amino acid racemization and tims thermal ionization mass spectrometry dates constrain the age of the deposits to between 390 and 550 ka while proxy evidence supports a correlation with oxygen isotope stage 11 this direct geologic evidence of a 20 decrease in polar ice during the middle pleistocene has important implications for the stability of ice sheets during warm interglaciations

climate an exceptionally long interglacial ahead today9s comparatively warm climate has been the exception more than the rule during the last 500 000 years or more if recent warm periods or interglacials are a guide then we may soon slip into another glacial period but berger and loutre argue in their perspective that with or without human perturbations the current warm climate may last another 50 000 years the reason is a minimum in the eccentricity of earth9s orbit around the sun

the laurentide and innuitian ice sheets during the last glacial maximum the late wisconsinan advance of the laurentide ice sheet started from a middle wisconsinan interstadial minimum 27 30 14 c ka bp when the ice margin approximately followed the boundary of the canadian shield ice extent in the cordillera and in the high arctic at that time was probably similar to present ice advanced to its late wisconsinan stage 2 limit in the northwest south and northeast about 23 24 14 c ka bp and in the southwest and far north about 20 21 14 c ka bp in comparison to some previous reconstructions of ice extent our current reconstruction has substantially more late wisconsinan ice in the high arctic where an innuitian ice sheet is generally acknowledged to have existed in the atlantic provinces where ice is now thought to have extended to the continental shelf edge in most places and on eastern baffin island where ice probably extended to the fiord mouths rather than to the fiord heads around most of the ice margin the late wisconsinan maximum ice extent either exceeded the extent of earlier wisconsinan advances or it was similar to the early wisconsinan advance ice marginal recession prior to 14 14 ck a bp occurred mainly in deep water and along the southern terrestrial fringe however heinrich event 1 probably drew down the entire central ice surface at 14 5 14 c ka bp sufficiently to displace the labrador sector outflow centre 900 km eastward from the coast of hudson bay the onset of substantial ice marginal recession occurred about 14 14 c ka bp in the northwest southwest and south but not until about 10 11 14 c ka bp in the northeast and in the high arctic thus the period of maximum ice extent in north america generally encompasses the interval from b24 21 to 14 14 c ka bp or considerably longer than the duration of the lgm defined as occurring during a period of low global sea level as well as during a time of relative climate stability b18 14 c ka bp the interval of advance of much of the laurentide ice sheet to its maximum extent between b27 14 c ka bp and b24 14 c ka bp coincides with a suggested interval of rapid fall in global sea level to near lgmlevels r 2001 elsevier science ltd all rights reserved

the anatomy of interglacial sea levels the relationship between sea levels and ice volumes during the last interglacial abstract the elevations and chronology of interglacial shorelines and other sea level indicators provide information on ice volumes for these earlier periods compared with today but as for the holocene the relationship between sea levels and ice volumes for earlier interglacials is not simple because of the planet s deformational gravitational and rotational response to changes in ice water loads glacio hydro isostasy in particular the pattern of global sea level for a particular interglacial will be a function of the earth and ocean response to ice loads applied before during and after the interglacial in question this paper examines the role of glacio hydro isostasy during these glacial cycles to make three key points the first is to demonstrate why interglacial sea levels cannot be interpreted directly in terms of ice volume the second is to illustrate the spatial variability that can be expected in interglacial sea levels because of the earth s isostatic response to changing ice and water loads and to demonstrate why observations from different localities should not be combined into a single sea level function without first correcting for differential isostatic effects the third addresses the question whether in the absence of perfect knowledge of the ice sheets and earth rheology inferences can be made about ice volumes during an interglacial we conclude that if these isostatic factors are ignored interpretations of interglacial sea levels can lead to serious errors in the inferences about ice volumes during the interglacials

sea level history during the last interglacial complex on san nicolas island california implications for glacial isostatic adjustment processes paleozoogeography and tectonics abstract san nicolas island california has one of the best records of fossiliferous quaternary marine terraces in north america with at least fourteen terraces rising to an elevation of 270 m above present day sea level in our studies of the lowest terraces we identified platforms at 38 36 m terrace 2a 33 28 m terrace 2b and 13 8 m terrace 1 uranium series dating of solitary corals from these terraces yields three clusters of ages 120 ka on terrace 2a marine isotope stage mis 5 5 120 and 100 ka on terrace 2b mis 5 5 and 5 3 and 80 ka mis 5 1 on terrace 1 we conclude that corals on terrace 2b that date to 120 ka were reworked from a formerly broader terrace 2a during the 100 ka sea stand fossil faunas differ on the three terraces isolated fragments of terrace 2a have a fauna similar to that of modern waters surrounding san nicolas island a mix of extralimital southern and extralimital northern species is found on terrace 2b and extralimital northern species are on terrace 1 on terrace 2b with its mixed faunas extralimital southern species indicating warmer than present waters are interpreted to be from the 120 ka high sea stand reworked from terrace 2a the extralimital northern species on terrace 2b indicating cooler than present waters are interpreted to be from the 100 ka sea stand the abundant extralimital northern species on terrace 1 indicate cooler than present waters at 80 ka using the highest elevations of the 120 ka platform of terrace 2a and assuming a paleo sea level of 6 m based on previous studies san nicolas island has experienced late quaternary uplift rates of 0 25 0 27 m ka these uplift rates along with shoreline angle elevations and ages of terrace 2b 100 ka and terrace 1 80 ka yield relative local paleo sea level elevations of 2 to 6 m for the 100 ka sea stand and 11 to 12 m for the 80 ka sea stand these estimates are significantly higher than those reported for the 100 ka and 80 ka sea stands on new guinea and barbados numerical models of the glacial isostatic adjustment gia process presented here demonstrate that these differences in the high stands are expected given the variable geographic distances between the sites and the former laurentide and cordilleran ice sheets moreover the numerical results show that the absolute and differential elevations of the observed high stands provide a potentially important constraint on ice volumes during this time interval and on earth structure

elevated marine deposits in bermuda record a late quaternary megatsunami deposits of coral bearing marine shell conglomerate exposed at elevations higher than 20 m above present day mean sea level msl in bermuda and the bahamas have previously been interpreted as relict intertidal deposits formed during marine isotope stage mis 11 ca 360 420 ka before present on the strength of this evidence a sea level highstand more than 20 m higher than present day msl was inferred for the mis 11 interglacial despite a lack of clear supporting evidence in the oxygen isotope records of deep sea sediment cores we have critically re examined the elevated marine deposits in bermuda and find their geological setting sedimentary relations and microfaunal assemblages to be inconsistent with intertidal deposition over an extended period rather these deposits which comprise a poorly sorted mixture of reef lagoon and shoreline sediments appear to have been carried tens of meters inside karst caves presumably by large waves at some time earlier than ca 310 360 ka before present mis 9 11 we hypothesize that these deposits are the result of a large tsunami during the mid pleistocene in which bermuda was impacted by a wave set that carried sediments from the surrounding reef platform and nearshore waters over the eolianite atoll likely causes for such a megatsunami are the flank collapse of an atlantic island volcano such as the roughly synchronous julan or orotava submarine landslides in the canary islands or a giant submarine landslide on the atlantic continental margin

electron spin resonance and radiocarbon dating of coral deposited by holocene tsunami events on curacao bonaire and aruba netherlands antilles abstract electron spin resonance esr dating of coral has become an efficient geochronological tool for studying the last 500 000 years this study presents results of esr dating of holocene coral from curacao bonaire and aruba leeward netherlands antilles the coral accumulated in rubble ridges and ramparts onshore and the depositional process is attributed to a series of tsunami events in addition to the calculation of equivalent dose d e values it is crucial for esr dating to obtain the correct d 0 value for each sample the annual dose rate d 0 estimation of the samples in this study is uncertain as the timing of the tsunami event and the residence time of a component of the dated sediment in different environments marine versus terrestrial is difficult to quantify assuming that the tsunami event deposited coral shortly after death the esr and 14 c ages of 22 samples reaching from 3650 to 128 years correspond well with each other this confirms the idea that the living coral reef was partly destroyed by tsunami events the esr dating uncertainties coincide with the variability of 14 c ages caused by the marine reservoir effect the local marine reservoir effect was estimated using four recent samples from 1920 and provided values between 375 and 595 yr bp

late quaternary sea level position evidence from bahamian carbonate deposition and dissolution cycles abstract the bahama islands offer a unique opportunity to examine late quaternary sea level position as the island group places significant constraints on the time and space boundary conditions for climatic events recorded there the bahamian archipelago extends as a series of large and small islands on shallow carbonate banks of various sizes for 1400 km across a climatic gradient wet in the northwest to dry in the southeast the entire island group is tectonically stable and consists solely of quaternary carbonate sediments with interspersed paleosols the islands reflect glacioeustatic sea level highstand positions in their eolian and subtidal suite of limestones a depositional record of platform flooding and carbonate sediment production a coeval record of phreatic cave development in the island s fresh water lenses also documents sea level highstand positions absolute dating of late pleistocene fossil corals and cave stalagmites by u th methods has produced an excellent record of the last interglacial marine isotope substage mis 5e holocene eolianites have been dated by 14 c to reveal platform flooding at 5000 ybp and sea level stabilization at 3000 ybp pleistocene eolianites have been dated by amino acid racemization analysis but subdivisons of the eolianites into separate mis 5a 5c and 5e deposits are controversial paleosols representing integrated aerosol dust deposition of 100 ka long platform exposure events during glaciations have been differentiated by paleomagnetic secular variation measurements previous interpretations of a beach unit to indicate a 20 m mis stage 11 sea level highstand and of large boulders to represent a mega tsunami appear to be incorrect phreatic caves in today s subaerial environment have been ascribed to mis 5e but some may have formed earlier carbonate deposition and dissolution cycles create a mass flux of co 2 sufficient to explain the atmospheric co 2 excursions of the quaternary

segmentation of the western taiwan active fault zone inferred from its structural analogy to the nankai trough region southwest japan abstract a west facing active fold and thrust structure is typified by the three thrust sheets soled by the frontal changhua central chelungpu and hindward shuangtung faults in the taichung area central western taiwan the least deformed changhua sheet comprises an n s trending frontal structural high and a parallel inner basin the chelungpu and shuangtung sheets deform an n s trending syncline that originates from an older basin the n s striking structures are traversed or overlain by ene wsw trending structures such as the ene striking tuntzuchiao fault and adjoining eastward bends of the northern tips of the chelungpu and shuangtung faults such transverse structures are located in three other areas of western taiwan near hsinchu north of chiayi and north of tainan the configuration of the island parallel and transverse structures mimics structural features of the rupture units of interplate earthquakes off southwest japan which are produced by right oblique subduction of the philippine sea plate along the nankai trough this suggests that the western taiwan active fault zone can be divided into five rupture areas 60 80 km long and may be controlled by left oblique convergent tectonics at the northern extension of the manila trench

on postglacial geoid subsidence over the equatorial oceans we develop two new spectral formalisms for the gravitationally self consistent solution of the sea level equation which governs the redistribution of glacial meltwater on a visco elastic earth the first is a purely spectral technique based on an extension of theory outlined by dahlen 1976 for determining the equilibrium oceanic tide on an elastic planet using this technique with a feasible spherical harmonic truncation level l 30 we can obtain convergence in the computed sea level variations within the degree range l 10 we also develop a second pseudospectral technique however which permits the construction of gravitationally self consistent solutions to much higher degree and order l 100 the pseudospectral formalism is employed here to develop a comprehensive physical explanation for the global pattern of present day sea level variations due to ongoing glacial isostatic adjustment in particular we focus upon a mechanism which we term equatorial ocean syphoning that acts to draw water toward the oceanic portion of the collapsing peripheral bulge that encircles previously glaciated regions the collapse of the forebulge induces a flow of water which is required to maintain hydrostatic equilibrium the syphoning mechanism dominates the relative sea level rsl variation in oceans in the far field of the ice sheets that is beyond the peripheral bulge during periods such as the interglacial of the past 4000 years during which the volume of the ice sheets has not apparently changed appreciably while at the same time isostatic adjustment persists the rsl change in the near field is in contrast dominated by the local vertical displacement of the solid surface finally comparison of gravitationally self consistent predictions of rsl change in the far field with the observational data at small pacific island sites has provided an upper bound of 1 to 2 m for the eustatic sea level rise produced by any recent last 3000 years melting of the antarctic ice sheet

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

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

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

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

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

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

neogene quaternary tectonic evolution of the leeward antilles islands aruba bonaire curacao from fault kinematic analysis aruba bonaire and curacao are islands aligned along the crest of a 200 km long segment of the east west trending leeward antilles ridge within the broad caribbean south america plate boundary zone presently characterized by east west right lateral strike slip motion the crust of the leeward antilles ridge represents the western segment of the cretaceous early cenozoic great arc of the caribbean which obliquely collided with the continental margin of northern south america in early cenozoic time following the collision the ridge was affected by folding and was segmented by oblique northwest striking normal faults that have produced steep sided northwest trending elongate islands and narrow shelves separated by deepwater sediment filled and fault controlled basins in this paper we present the first fault slip observations on the neogene carbonate rocks that cover large areas of all three islands our main objective is to quantify the timing and nature of neogene to quaternary phases of faulting and folding that have affected the structure and topography of this area including offshore sedimentary basins that are being explored for their petroleum potential these data constrain three fault phases that have affected aruba bonaire and curacao and likely the adjacent offshore areas 1 nw se directed late paleogene compression 2 middle miocene syndepositional nnw sse to nne ssw extension that produced deep rift basins transverse to the east west trending leeward antilles ridge and 3 pliocene quaternary nne trending compression that produced nw se trending anticlines present on aruba curacao and bonaire islands our new observations that include detailed relationships between striated fault planes paleostress tensors and bedding planes show that prominent bedding dips of neogene limestone on aruba bonaire and curacao were produced by regional tectonic shortening across the entire leeward antilles ridge rather than by localized syndepositional effects as proposed by previous workers we interpret pliocene quaternary nne directed shortening effects on the leeward antilles ridge as the result of northeastward extrusion or tectonic escape of continental areas of western venezuela combined with southeastward shallow subduction of the caribbean plate beneath the ridge

sea level history of past interglacial periods from uranium series dating of corals curacao leeward antilles islands curacao has reef terraces with the potential to provide sea level histories of interglacial periods ages of the hato upper unit of the lower terrace indicate that this reef dates to the last interglacial period marine isotope stage mis 5 5 on curacao this high sea stand lasted at least 8000 yr 126 to 118 ka elevations and age of this reef show that late quaternary uplift rates on curacao are low 0 026 0 054 m ka consistent with its tectonic setting ages of 200 ka for corals from the older cortalein unit of the lower terrace correlate this reef to mis 7 with paleo sea level estimates ranging from 3 3 m to 2 3 m the estimates are in agreement with those for mis 7 made from other localities and indicate that the penultimate interglacial period was a time of significant warmth on a par with the present interglacial period the 400 ka mis 11 middle terrace i on curacao dated by others may have formed from a paleo sea level of 8 3 to 10 0 m or less likely 17 m to 20 m the lower estimates are conservative compared to previous studies but still require major ice sheet loss from greenland and antarctica

comparison between holocene and marine isotope stage 11 sea level histories the exceptionally long interglacial warm period known as marine isotope stage 11 mis 11 428 397 ky ago vs ky vs kyr is often considered as a potential analogue for future climate development in the absence of human influence we use a new high resolution sea level record a globally integrated ice volume signal to compare mis 11 and the current interglacial holocene it is found that sea level rise into both interglacials started over similar timescales relative to the respective insolation increases and progressed up to 50 m at similar rates of 1 0 1 2 m per century subsequent weak insolation changes anomalously prolonged the mis11 deglaciation over more than 20 ky the main sea level highstand was achieved at the second mis 11 insolation maximum with a timing closely equivalent to that of the holocene highstand compared to its single insolation maximum consequently while mis 11 was an exceptionally long period of interglacial warmth its ice volume minimum sea level highstand lasted less than 10 ky which is similar to the duration of other major interglacials comparison of the ends of mis 11 and the holocene based on timings relative to their respective maxima in mean 21 june insolation at 65 n suggests that the end of holocene conditions might have been expected 2 0 2 5 ky ago instead interglacial conditions have continued with co2 temperature and sea level remaining high or increasing this apparent discrepancy highlights the need to consider that a comparisons may need to focus on other orbital control indices in which case the discrepancy can vanish and or b the feedback mechanisms that dominate the planetary energy balance may have become decoupled from insolation during the past 2millennia

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

early jurassic volcanic rocks in the xiongcun district southern lhasa subterrane tibet implications for the tectono magmatic events associated with the early evolution of the neo tethys ocean abstract early mesozoic late triassic to middle jurassic igneous rocks in the southern lhasa subterrane tibet record important information on the early tectono magmatic evolution of the neo tethys ocean this paper presents petrological geochronological and geochemical data for the xiongcun formation ignimbrites to constrain the petrogenesis and tectonic setting of these rocks in the southern lhasa subterrane the xiongcun formation is dominated by andesitic and dacitic rocks these rocks yield early jurassic 195 176 ma zircon u pb ages and display typical arc like geochemical signatures being enriched in large ion lithophile elements e g rb ba and u and depleted in high field strength elements e g nb ta and ti sr nd pb hf isotopic compositions are highly depleted these chemical and isotopic data suggest that the xiongcun formation ignimbrites probably formed in an intra oceanic island arc setting related to the northward subduction of the neo tethys oceanic slab the parental magmas were derived from a depleted mantle source modified by fluids released from the neo tethys oceanic slab combined with previously reported data we suggest that the volcanic rocks in the early jurassic xiongcun and yeba formations of the southern lhasa subterrane were generated by a single subduction system but developed on oceanic and continental crust respectively

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

a 300 000 yr coral reef record of sea level changes mururoa atoll tuamotu archipelago french polynesia abstract the accurate dating of fossil coral reefs is of prime importance in determining the timing of deglaciation events and thus understanding the mechanisms driving glacial interglacial cycles so far the most useful coral reef records of past sea level changes are those related to the last deglaciation and the last interglacial period u th ages for older isotopic stages are more limited due to the scarcity of datable material reflecting diagenetic alteration most data are from emergent parts of reefs and reef terraces in active subduction zones where relative sea level records may be biased by variations in rates of tectonic uplift new constraints on sea level changes over the past 300 000 yr are based on high precision u series age measurements of successive reef units on mururoa these have been cored in four continuous 300 m long drill holes with seaward inclinations of 30 to 45 on the northeastern rim of the atoll past sea level positions have been calculated from the radiometric ages of corals by correcting the present depth of subsurface horizons both for thermal subsidence and for depositional palaeodepth the location of this atoll at a considerable distance from former ice sheets far field minimises the influence of glacio isostatic rebound prominent units formed during four periods of relative sea level highstands including the holocene and stages 5 125 ka 7 212 ka and 9 332 ka these are primarily composed of coralgal frameworks that grew in very shallow water three periods of relative low stand correspond to stages 2 17 23 ka 4 60 ka and 8 270 ka during which small reefs developed in association with large bioclastic accumulations good agreement with the timing of sea level changes based on oxygen isotope measurements in deep sea cores is noted for most of the dated reef units we report here the first accurate coral record of the last glacial maximum in the pacific 135 143 m below the present sea surface suggesting that sea level may have been lower than expected during this period

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

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

sea level highstands over the last 500 000 years evidence from the ironshore formation on grand cayman british west indies abstract the ironshore formation up to 19 m thick in the rogers wreck point area of grand cayman is divided into the unconformity bounded units a b c and d the unconformities are highlighted by caliches and or terra rossa th u dates from aragonitic corals indicate that unit a formed at 400 ka unit b 346 ka unit c 229 ka and unit d 131 ka these ages correlate with the highstands of the last four interglacial periods and probably represent marine isotope stages 5 unit d 7 unit c 9 unit b and 11 unit a the limestones in units a d which have similar biotic and lithologic characteristics represent deposition in shallow water on a narrow coastal shelf unit a has a high faunal diversity and was deposited in open marine conditions whereas units b c and d were deposited in quieter water lagoons that probably had fringing reefs along their sea ward edges although grand cayman is located on the cayman ridge close to an active spreading center and transform fault the island has undergone little or no vertical movement over the last 500 ky available evidence indicates that sea level at the time of deposition of each unit relative to present sea level was unit a 9 0 to 5 5 m unit b 3 0 to 0 5 m unit c 2 5 to 1 1 m and unit d 2 5 to 6 0 m these data are good estimates of eustatic sea level highstands over the last 500 ky