esr dating of raised coral reefs from kish island persian gulf electron spin resonance esr dating of raised coral reefs from kish island persian gulf iran was used for the calculation of uplift rates from the methodological point of view it has been demonstrated that concentrations of uranium as needed for the calculation of dose rates determined by instrumental neutron activation analyses were significantly lower than the results of inductively coupled plasma mass spectrometry and are probably systematically underestimated the esr ages for the corals show no increase with elevation as was expected due to field observations this apparent discrepancy is explained by the dicyclic nature of the palaeo reef average uplift rates for kish island are between 0 13 and 0 24 mm a 1 this is consistent with previous estimates based on 230th 234u dating of raised marine deposits from the nearby iranian mainland and qeshm island strait of hormuz but contrary to results based on 14c dating that predicted uplift rates as high as 3 mm a 1 in that area it is once more demonstrated that 14c dates 20 ka from this context often have to be interpreted as minimum ages

comparison of esr ages of corals from marine terraces with 14c and 230th 234u ages the ages of corals from marine terraces in the ryukyu islands of japan have been determined by electron spin resonance esr esr ages deduced from the total dosage of natural radiation taking the time dependent dose rate due to 238 u series disequilibrium into account agreed fairly well with those determined by 14 c and 230 th 234 u dating the esr age can be extended well beyond the limits of 14 c dating 50 000 years and the 230 th 234 u method 300 000 years to a million years

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

forcing mechanisms for mid cretaceous black shale formation evidence from the upper aptian and lower albian of the vocontian basin se france calcareous nannoplankton palynomorph benthic foraminifera and oxygen isotope records from the supraregionally distributed niveau paquier early albian age oceanic anoxic event 1b and regionally distributed niveau kilian late aptian age black shales in the vocontian basin se france exhibit variations that reflect paleoclimatic and paleoceanographic changes in the mid cretaceous low latitudes to quantify surface water productivity and temperature changes nutrient and temperature indices based on calcareous nannofossils were developed the nutrient index strongly varies in the precessional band whereas variations of the temperature index reflect eccentricity since polar ice caps were not present during the mid cretaceous these variations probably result from feedback mechanisms within a monsoonal climate system of the mid cretaceous low latitudes involving warm humid and cool dry cycles a model is proposed that explains the formation of mid cretaceous black shales through monsoonally driven changes in temperature and evaporation precipitation patterns the lower albian niveau paquier which has a supraregional distribution formed under extremely warm and humid conditions when monsoonal intensity was strongest bottom water ventilation in the vocontian basin was diminished probably due to increased precipitation and reduced evaporation in regions of deep water formation at low latitudes surface water productivity in the vocontian basin was controlled by the strength of monsoonal winds the upper aptian niveau kilian which has a regional distribution only formed under a less warm and humid climate than the niveau paquier low latitude deep water formation was reduced to a lesser extent and or on regional scale only the threshold for the formation of a supraregional black shale was not reached the intensity of increases in temperature and humidity controlled whether black shales developed on a regional or supraregional scale at least in the vocontian basin the increased preservation of organic matter at the sea floor was more significant in black shale formation than the role of enhanced productivity

record of mis 5 sea level highstands based on u th dated coral terraces of haiti abstract new geomorphologic investigations and new u th series dates from haiti northwestern peninsula confirm the age of coral reef terraces assigned to mis 5 5 130 ka mis 5 3 107 ka and mis 5 1 83 ka sea level peaks they also provide evidence for a second high sea level occurring some thousand years before 118 ka and indicate a second mis 5 1 sea level stand at about 76 ka these results are in agreement with the raised terraces of barbados although the staircase of haiti consists of four steps compared to eight the haitian sequence can be compared with the maximal number of distinct mis 5 sea level highstands recorded in the world from coral reef tracts and their relative height above or below present sea level three mis 5 5 sea level changes have been recognized with sea level oscillating above or near the present level until 122 ka only dropping then rising to 11 m below present sea level at 120 ka three high frequency sea level oscillations occurred during mis 5 3 and a fourth during mis 5 3 5 2 two or three events may have occurred during mis 5 l according to whether the 73 ka event is considered to belong to mis 5 1

atmospheric carbon dioxide and early eocene climate a general circulation modeling sensitivity study abstract the early eocene was the warmest time interval of the past 65 million years we have investigated the hypothesis that the warm climate of the early eocene may have been caused by higher than present levels of atmospheric carbon dioxide co2 we have used an atmospheric general circulation model the ncar genesis model coupled to a land surface model and a mixed layer ocean to examine the sensitivity of early eocene climate to varying levels of atmospheric co2 model cases contained a description of the early eocene earth and included either 300 560 or 1680 ppm atmospheric co2 climate responses to increased atmospheric co2 include 1 increased mean annual global temperature by 2 6 c and decreased latitudinal surface temperature gradients 2 maximum warming at high latitudes especially in the winter season 3 increased mean global precipitation 4 increased high latitude clouds in comparison with geological paleoclimate data the climate response to increased co2 does not appear to explain completely the early eocene latitudinal surface temperature gradient for example with the 1680 ppm co2 case high latitude oceans and continents are minimally warm enough to match paleoclimate data while low latitude regions are overly warm when compared to sea surface temperature reconstructions we conclude that co2 was very likely at least double the present level during the early eocene and contributed to the overall character of early eocene climate however consideration of increased poleward oceanic heat transport and or other factors may be required to produce model results that more closely agree with marine and terrestrial paleoclimate data especially at low latitudes

mechanisms of thermohaline mode switching with application to warm equable climates abstract a three box model of haline and thermal mode overturning is developed to study thermohaline oscillations found in a number of ocean general circulation models and that might have occurred in warm equable paleoclimates by including convective adjustment modified to represent the localized nature of deep convection the box model shows that a steady haline mode circulation is unstable for certain ranges of freshwater forcing vertical diffusivity a self sustained oscillatory circulation is found in which haline thermal mode switching occurs with a period of centuries to millennia it is found that mode switching is most likely to occur in warm periods of earth s history with relative to the present climate a reduced pole ndash uator temperature gradient an enhanced hydrological cycle and somewhat smaller values of oceanic diffusivities

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

climatic responses to tropical sea surface temperature changes on a greenhouse earth the uncertainty associated with tropical sea surface temperatures ssts during past greenhouse climates may have important and unaccounted for effects we explore early paleogene climatic sensitivity to changes in tropical subtropical ssts with a general circulation model we demonstrate that tropical sst changes have local and far field climatic effects underscoring their importance in understanding greenhouse climates the responses of winds upwelling and surface water balance to tropical sst changes are substantial our results indicate that current tropical sst reconstructions may have a significant cool bias despite corrections and that the existence of hot 30 c tropical ssts may be realistic for greenhouse climate intervals including the eocene

a one million year long sequence of marine terraces on sumba island indonesia abstract an exceptional sequence of raised coral reef terraces is visible at cape laundi on the north coast of the island of sumba in the savu sea in which at least eleven terraces wider than 100 m six of them even being over half a kilometer wide are geomorphologically distinguishable between an ancient patch reef now at 475 m and the present sea level esr date estimations of almost unrecrystallized corals most of them in situ make possible a tentative identification of the terraces corresponding to isotope stages 15 ca 600 ka ago and 9 ca 330 ka ago when the uplift trend deduced from the present altitude of dated terraces 0 49 0 01 mm yr is extrapolated to the whole raised section most geomorphological features appear to correspond to interglacial stages of the astronomically calibrated oxygen isotope record up to stage 27 ca 0 99 ma beyond the matuyama jaramillo geomagnetic boundary the upper terraces would in this case be twice as old as previously estimated ca 0 5 ma main terraces seem to correspond to high sea levels at certain interglacial stages and substages but in some cases the action of low sea levels at glacial stages cannot be ruled out for terraces between 30 and 70 m in altitude th u and esr dates reveal that aragonitic corals at similar elevations may differ in age as much as 100 ka this can be explained by taking into account a polycyclic origin for several terraces reconstructions available of changes in the eustatic sea level during the last 250 kyr and the fact that coral reef development may have been scattered at some periods only without totally covering subjacent older formations the sumba sequence of marine terraces at cape laundi is among the longest and most complete for the past million years reported in the literature its relatively good state of preservation will probably give impetus to a number of new studies on the chemical physical isotopic morphological palaeoclimatic pedological ecological and diagenetic changes which have occurred during the past one million years

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

coastal uplift rate at matanzas cuba inferred from mis5e phreatic overgrowths on speleothems many morphological elements in cuba s landscape e g marine terraces tidal notches demonstrate that coastal uplift has taken place but the rate at which this occurs is not known carbonate phreatic overgrowths on speleothems have been found in a cave in central north cuba 1 km from the present coastline at 16 m asl they form exceptional and unique mushroom shaped speleothems and balconies decorating the walls of the rooms these phreatic overgrowths on speleothems pos formed at the oscillating air water interface in sea level controlled anchialine lakes u th dating of these overgrowths suggests ages that are compatible with the marine isotope stage 5e i e 130 115 ka these pos have fixed this sea level highstand and demonstrate that this part of cuba has been subjected to a much lower uplift rate than previously reported i e less than 0 1 mm a 1 since the last interglacial this article is protected by copyright all rights reserved

esr dating of fossil shells in the lutzow holm bay region east antarctica abstract the authors investigate esr dating of in situ fossil aragonitic shells from the emerged marine sediments in the lutzow holm bay region east antarctica to compare esr ages with ams 14c dates and to discuss late pleistocene chronology from the esr ages the ams 14c ages of late pleistocene for the samples 33 43 ka seem to be underestimated and to be much closer to the marine isotope stage mis 4 5 or mis 6 7 rather than to mis 3 our results suggest that further dating studies as well as 14c dating should be made in the study area by using various techniques

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

water mass circulation on demerara rise during the late cretaceous based on nd isotopes abstract circulation in the north atlantic during the late cretaceous has implications for poleward heat transport and nutrient distribution during an extreme greenhouse interval with episodes of ocean anoxia nd isotopes of fossil fish teeth and debris represent one of the few water mass tracers that can be used to reconstruct deep ocean circulation we present nd isotopic data interpreted as bottom water values for 290 samples from three ocean drilling program sites on demerara rise sites 1258 1260 and 1261 along with 102 analyses from four other north atlantic sites cape verde goban spur bermuda rise and blake nose that provide additional geographic and bathymetric control our results confirm the presence of a water mass with low end values 14 to 17 that are believed to be influenced by continental material during local water mass formation at low latitudes this demerara bottom water dbw is the primary water mass in the region from the cenomanian to coniacian and from the late campanian through early maastrichtian following a hiatus of 10 my a positive 8 end unit excursion occurs during ocean anoxic event 2 oae2 that cannot be explained by changes in weathering inputs diagenesis or magmatic sources of nd instead it appears to represent an influx of bottom waters sourced from the tethys or north atlantic this replacement of dbw during oae2 argues for decreased production of dbw or enhanced production of tethys north atlantic waters during peak greenhouse conditions from the late campanian through early maastrichtian dbw becomes the only water mass recorded at demerara rise and it appears to expand to abyssal depths at cape verde in the campanian this water mass is ultimately replaced by waters that appear to be sourced from the north atlantic starting in the late maastrichtian observed variations in circulation in the tropical north atlantic during the late cretaceous can account for extensive deposition of black shales in the region prior to the hiatus as well as local warming during a global cooling event in the maastrichtian

model simulation of the cretaceous ocean circulation three dimensional numerical ocean circulation model experiments that were designed to evaluate the circulation characteristics for the mid cretaceous 100 million years ago show that the primary direction of flow through the tethys ocean was eastward in contrast a westward flowing circumglobal tethys current has been a consistent feature of earlier reconstructions of cretaceous ocean circulation the model studies demonstrate that i ocean circulation is sufficiently sensitive to the role of continental positions sea level and climate to limit the application of modern analogs to past circulations and ii reconstructions based on limited biogeographic data may not provide unique surface circulation patterns

late quaternary uplift along the north america caribbean plate boundary evidence from the sea level record of guantanamo bay cuba abstract the tectonic setting of the north america caribbean plate boundary has been studied intensively but some aspects are still poorly understood particularly along the oriente fault zone guantanamo bay southern cuba is considered to be on a coastline that is under a transpressive tectonic regime along this zone and is hypothesized to have a low uplift rate we tested this by studying emergent reef terrace deposits around the bay reef elevations in the protected inner part of the bay are 11 12 m and outer coast wave cut benches are as high as 14 m uranium series analyses of corals yield ages ranging from 133 ka to 119 ka correlating this reef to the peak of the last interglacial period marine isotope stage mis 5 5 assuming a span of possible paleo sea levels at the time of the last interglacial period yields long term tectonic uplift rates of 0 02 0 11 m ka supporting the hypothesis that the tectonic uplift rate is low nevertheless on the eastern and southern coasts of cuba east and west of guantanamo bay there are flights of multiple marine terraces at higher elevations that could record a higher rate of uplift implying that guantanamo bay may be anomalous southern cuba is considered to have experienced a measurable but modest effect from glacial isostatic adjustment gia processes thus with a low uplift rate guantanamo bay should show no evidence of emergent marine terraces dating to the 100 ka mis 5 3 or 80 ka mis 5 1 sea stands and results of the present study support this

can increased poleward oceanic heat flux explain the warm cretaceous climate the poleward transport of heat in the mid cretaceous 100 ma is examined using an idealized coupled ocean atmosphere model the oceanic component consists of two zonally averaged basins representing the proto pacific and proto indian oceans and models the dynamics of the meridional thermohaline circulation the atmospheric component is a simple energy and moisture balance model which includes the diffusive meridional transport of sensible heat and moisture the ocean model is spun up with a variety of plausible cretaceous surface temperature and salinity profiles and a consistent atmosphere is objectively derived based on the resultant sea surface temperature and the surface heat and freshwater fluxes the coupled model does not exhibit climate drift multiple equilibria of the coupled model are found that break the initial symmetry of the ocean circulation several of these equilibria have one cell northern or southern sinking thermohaline circulation patterns two main classes of circulation are found circulations where the densest water is relatively cool and is formed at the polar latitudes and circulations where the densest water is warm but quite saline and the strongest sinking occurs at the tropics in all cases significant amounts of warm saline bottom water are formed in the proto indian basin which modify the deepwater characteristics in the larger proto pacific basin temperatures in the deep ocean are warm 10 17 c in agreement with benthic foraminiferal oxygen isotope data the poleward transport of heat in the modeled cretaceous oceans is larger than in some comparable models of the present day thermohaline circulation and significantly larger than estimates of similar processes in the present day ocean it is consistently larger in the polar sinking cases when compared with that seen in the tropical sinking cases but this represents an increase of only 10 the largest increase over present day model transports is in the atmospheric latent heat transport where an increased hydrological cycle especially in the tropical sinking cases contributes up to an extra 1 pw of poleward heat transport better constraints on the oceanic deepwater circulation during this period are necessary before the meridional circulation can be unambiguously described

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

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

sea level oscillations during the last interglacial highstand recorded by bahamas corals whether sea level was stable during the last interglacial remains a subject of debate an analysis of the u th ages of coral reefs in the bahamas corrected for open system behaviour confirms the presence of at least one oscillation within the sea level highstand

new uranium series ages of the waimanalo limestone oahu hawaii implications for sea level during the last interglacial period abstract the waimanalo formation limestone of oahu has been correlated with the last interglacial period based on u series dating of corals by t l ku and colleagues the limestone consists of growth position corals and overlying coral conglomerate an apparent bimodal distribution of ages for the growth position corals mean age 133 ka and the overlying coral conglomerate mean age 119 ka has been interpreted to represent two distinct high stands of sea that occurred within the last interglacial period both growth position corals and overlying conglomerate coral occur in an outcrop east of kaena point and consist mainly of pocillopora and porites u series ages of growth position corals that show closed system conditions are 120 3 ka and 127 4 ka overlying conglomerate corals have u series ages that range from 120 3 ka to 138 4 ka at kahe point conglomerate corals have ages of 120 3 ka and 134 4 ka these data show that the growth position corals are not systematically older than the conglomerate corals thus there is no evidence for two distinct high stands of sea waimanalo deposits at kahe point and mokapu point new u series ages of 134 4 ka and 127 3 ka have beach deposits as high as 12 5 m and at mokapu point growth position corals as high as 8 5 m a last interglacial sea level stand of 8 5 to 12 5 m conflicts with estimates of 6 m from a number of tectonically stable coastlines and islands in the western atlantic ocean we infer therefore that oahu may be undergoing uplift at a low rate this uplift may be due to compensatory lithospheric flexure because the island of hawaii has been subsiding throughout much of the quaternary from volcanic loading because of this possible uplift oahu and islands like it elsewhere in the pacific cannot be used as reference points for sea level during the last interglacial period

continental runoff and early cenozoic bottom water sources the dominance of warm saline bottom water during the mid cretaceous and the early cenozoic has been inferred from sea floor sediment records an interpretation supported by early ocean general circulation model experiments thermohaline circulation depends in part on upper ocean salinities however early ocean models neglected continental runoff a potentially critical factor in the salinity budget of the surface ocean our early eocene ocean model sensitivity tests show that model deep water sources can be enhanced diminished or turned off by varying the treatment of continental runoff in the atmosphere ocean moisture flux calculation failure to treat surface runoff adequately thus has important implications for the simulation of thermohaline flow and formation of warm saline bottom water variations in runoff could have led to rapid changes in the relative importance of high latitude versus subtropical deep water such as may have occurred during the late paleocene early eocene boundary interval 53 6 56 2 ma

whole rock aminostratigraphy and quaternary sea level history of the bahamas abstract the surficial geology of the tectonically stable bahamian archipelago preserves one of the most complete records of middle to late quaternary sea level highstand cycles in the world however with the exception of deposits from marine isotope substage mis 5e fossil corals for radiometric dating of this rich stratigraphic sequence are rare this study utilizes the previously published independent lithostratigraphic framework as a testing ground for amino acid racemization in whole rock limestone samples at least six limestone soil couplets provide a relative age sequence of events that encompass as many interglacial glacial cycles d alloisoleucine l isoleucine data fall into six clusters or aminozones on the basis of independent dating and the inferred correlation with global mis the ages of several aminozones are known while the ages of others are calculated from calibrated amino acid geochronology this study demonstrates the utility of the whole rock aminostratigraphy method for dating and correlating widespread emergent marine deposits constitutes the first regional geochronological framework for the bahamas and highlights major sea level events over the past half million years

trends in stability of dynamically stable breakwaters the reshaping of dynamically stable breakwaters was studied subject to variations in armour stone gradation and shape wave characteristics and duration of wave attack from head on waves in a two dimensional wave flume tests were undertaken at the coastal engineering research laboratory of queen s university kingston canada using irregular waves profiles of the structure during the various stages of reshaping were measured using a semi automatic profiler developed for this study the volume of stones and the initial berm width required for development of a stable profile along with the extent to which the toe of the structure progressed seaward were chosen as the characteristic parameters of the reshaped breakwater the results indicated that the toe width formed as a result of reshaping and the area of stones required for reshaping were dependent on the wave height gradation of the armour stone and duration of the storm the initial berm width required for reshaping was also found to be dependent on the wave height armour stone gradation percentage of rounded stones in the armour and the duration of the storm

esr and u th dating results for last interglacial coral reef terraces at the northern coast of cuba abstract fossil coral reef terraces at the northern coast of cuba in the vicinity of the bay of matanzas are forming a prominent flight of terraces these terraces were already studied by several investigators but a chronological classification based on numerical dating is still missing in this study we focus on the lowest unit the seboruco terrace which is assumed to be of mis 5e age the morphology of the seboruco terrace and associated sea level markers reef crests and notches were mapped and their altitude was measured over the whole study area in the field and by using remote sensing the fossil corals building up the terrace were surveyed in numerous natural outcrops the species of the fossil coral reefs were determined and subdivided in different facies zones fossil corals were taken for numerical dating by electron spin resonance esr and uranium series u th to establish a chronology of the mis 5e coral reef formation both dating techniques yielded age results in good agreement with each other and the stratigraphic context corresponding to the field evidence the age data indicates one mis 5e sea level highstand around 126 ka some younger esr ages may be explained by the recrystallization of aragonitic corals and or by u leaching at one locality east of matanzas the radiometric results for an underlying coral reef body suggest an mis 7 age the sea level markers for the mis 5e highstand range from 5 5 m a s l reef crest to a maximum of 7 m notches west of the bay of matanzas resulting in relatively low uplift rates of 0 003 m ka and 0 036 m ka when applying early mis 5e sea level estimates from tectonically stable coasts in the caribbean between 2 5 m and 6 6 m inside the bay of matanzas itself the elevation of sea level markers increases to more than 10 m a s l indicating a stronger uplift rate of 0 027 m ka to 0 060 m ka here

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

a simulation of mid cretaceous climate a series of general circulation model experiments utilizing genesis have been completed for the mid cretaceous based on geography variable atmospheric carbon dioxide concentrations 2 to 6 times present day concentrations and variable poleward oceanic heat flux 6 to 1 2 1015 w increased from present day by combining all three major variables co2 geography and oceanic heat flux the distribution of mid cretaceous temperatures can be achieved in the simulations increased co2 is required to promote global warmth and increased oceanic heat flux is required to prevent the tropics from overheating with higher levels of co2 four times present day co2 with 1 2 1015 w provided the best match to the distribution of mid cretaceous data the best match to the cretaceous observations was achieved with a globally averaged surface temperature increase of 6 2 c at the lower end of past estimates of mid cretaceous warmth this value may be a better estimate of mid cretaceous global warming finally the model experiments can be used to provide a paleocalibration of the global warming expected for a doubling of atmospheric carbon dioxide the best estimates for the mid cretaceous appear to be a 2 5 to 4 0 c sensitivity in the mid to upper range of the sensitivity of current climate models used to assess future global change

storm evolution characterization for analysing stone armour damage progression abstract storm evolution is fundamental for analysing the damage progression of the different failure modes and establishing suitable protocols for maintaining and optimally sizing structures however this aspect has hardly been studied and practically the whole of the studies dealing with the subject adopt the equivalent triangle storm as against this approach two new ones are proposed the first is the equivalent triangle magnitude storm model etms whose base the triangular storm duration d is established such that its magnitude area describing the storm history above the reference threshold level which sets the storm condition ht equals the real storm magnitude the other is the equivalent triangle number of waves storm etnws where the base is referred in terms of the real storm s number of waves nz three approaches are used for estimating the mean period tm associated to each of the sea states defining the storm evolution which is necessary to determine the full energy flux withstood by the structure in the course of the extreme event two are based on the jonswap spectrum representativity and the other uses the bivariate gumbel copula hs tm resulting from adjusting the storm peaks the representativity of the approaches proposed and those defined in specialised literature are analysed by comparing the main armour layer s progressive loss of hydraulic stability caused by real storms and that relating to theoretical ones an empirical maximum energy flux model is used for this purpose the agreement between the empirical and theoretical results demonstrates that the representativity of the different approaches depends on the storm characteristics and point towards a need to investigate other geometrical shapes to characterise the storm evolution associated with sea states heavily influenced by swell wave components

high rates of sea level rise during the last interglacial period sea level during the last interglacial stood at least 4 m higher than at present with evidence of short term fluctuations of up to 10 m a new continuous sea level record from the red sea and coral ages suggest that during these fluctuations sea level changes were on the order of 1 6 m per century

paleocean circulation during the last deglaciation a bipolar seesaw hughen et al 1998 have documented that during the first 200 years of younger dryas time the 14c content of atmospheric co2 increased by 50 and that during the remainder of this 1200 year duration cold event it steadily declined the initial increase in 14c c was likely the result of a reduction in the atlantic s conveyor circulation however were the subsequent radiocarbon decline due to the rejuvenation of this potent heat pump then it is difficult to understand why the climate conditions in the northern atlantic basin remained cold throughout the younger dryas modeling exercises by stocker and wright 1996 mikolajewicz 1998 and schiller et al 1998 show that if the conveyor is terminated the transfer of radiocarbon into the deep sea shifts to the southern ocean thereby stabilizing the atmospheric 14c c ratio paleoclimatic evidence from the antarctic continent suggests that this model based scenario might have been played out in the real world while the younger dryas cooling has been documented in many places around the world including new zealand denton and hendy 1994 sowers and bender 1995 using their 18o in o2 based correlation between the ice core 18o in ice records for antarctica and greenland have demonstrated that in antarctica the younger dryas was a time of maximum warming the point of this paper is that the steep rise in 18o rise in antarctic ice which commenced close to the onset of the younger dryas might have been caused by heat released to the atmosphere in response to an increase in deep sea ventilation in the southern ocean

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

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

late albian dinoflagellate cyst paleobiogeography as indicator of asymmetric sea surface temperature gradient on both hemispheres with southern high latitudes warmer than northern ones abstract late albian temperature sensitive dinoflagellate cysts are characterized in order to better understand mid cretaceous sea surface temperature gradients distribution maps of thirty seven species recovered from one hundred fifty outcrops and deep sea drilling holes odp dsdp sites located from low and high paleolatitudes over the two hemispheres 75 n 70 s are encountered fifty years of published data available in eighty seven articles have been considered and synthesized using a database coupled with a geographical information system gis the continuous and disjoint biogeographic patterns of dinocyst species along latitudes define seven climatic belts four in the northern hemisphere high mid high mid low low latitude belts and three in the southern hemisphere low mid low mid high latitude belts dinocysts restricted along latitudes are temperature sensitive species limit ranges of temperature sensitive dinocysts of mid low and mid high latitude belts reveal mixing belts located at 40 45 n and 50 70 s they represent major palaeofrontal systems as paleosubtropical fronts with strongly mixed water column the northern frontal system 40 45 n was located as in the modern ocean the large southern frontal system 50 s 70 s was 10 20 poleward to antarctica semi quantitative temperature range limits for mid cretaceous dinoflagellates and sst gradients in the two hemispheres are suggested by setting dinocyst climatic belts against estimated 18o temperature curve from fish teeth a paleoecological classification is suggested latitudinal distribution of extant temperature sensitive dinoflagellate cysts follows the asymmetric modern temperature gradient asymmetric latitudinal ranges of late albian dinocyst species of mid low latitude belts restricted between 45 n and 70 s demonstrate asymmetric temperature gradients with southern high latitudes being warmer than northern high latitudes

the quaternary coral reef tracts of hateruma ryukyu islands japan the island of hateruma is located at the southwestern end of the ryukyu island chain and covers an area of about 15 km2 with its highest point at 59 5 m a s l the morphology of hateruma is characterized by an eight step staircase i to viii after ota et al 1982 most of which eroded into the previously formed coral reefs ii and iv to viii this study presents 100 age estimations on 43 coral samples using electron spin resonance esr alpha and mass spectrometric u series methods the dating results imply that the ryukyu limestone was predominantly formed during oxygen isotope stages 7 and 5e two age estimates of around 300 ka suggest an earlier reef building period the main problem for establishing the quaternary history of hateruma lies in the fact that the coral ages and the staircase morphology do not correlate additionally it is difficult to distinguish autochthonous from allochthonous samples the latter having possibly been relocated by tsunamis corals relating to substages 5a and 5c around 75 and 105 ka respectively are found in the immediate vicinity of much older samples the results of this study prove the disappointing fact that hateruma cannot yet be used as a tool for reconstructing palaeo sea levels

esr in the 21st century from buried valleys and deserts to the deep ocean and tectonic uplift abstract electron spin resonance esr dating can date many materials including hydroxyapatite in enamel and some fish scales aragonite and calcite in corals molluscs some travertine and calcrete and quartz from ash fluvial deposits and some flint dating studies using these materials have numerous potential applications in many varied quaternary settings esr dating uses signals resulting from trapped charges created by radiation in crystalline solids ages are calculated by comparing the accumulated radiation dose in the dating sample with the internal and external radiation dose rates produced by natural radiation in and around the sample and produced by cosmic radiation when compared to other dating techniques age agreement has been excellent for teeth corals molluscs and quartz recent improvements have included using a more complex modelling technique to calculate the cosmic dose rates and more detailed modelling techniques for dealing with variable external dose rates methods in development include using quartz from buried fluvial valleys to date geomorphic surfaces and using the signals in barnacles and benthic foraminifera for dating fossils or their associated sediment new chronometer applications recently developed include using coral and mollusc dates to build sealevel curves and to monitor volcanic activity and tectonic uplift using tooth and mollusc dates to assess water availability in deserts and using isochron data to assess u uptake processes into teeth when coupled with other geochemical and geomorphological techniques esr can provide the chronometric control to build paleoclimatic and other paleoenvironmental records many other applications are possible from heating studies for artefacts to dating sulphates and other minerals on distant planets

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

continental drift and the global pattern of sedimentation the breakup of pangaea through rifting and separation of the continents has special implications for the global pattern of sedimentation the important initial conditions of pangaea are area elevation the nature of the drainage and climate the development of interior uplifts associated with rifting caused significant reorganization of drainage systems rifting and continental breakup result in unique sediment sequences on passive margins

discerning the timing and cause of historical mortality events in modern porites from the great barrier reef the life history strategies of massive porites corals make them a valuable resource not only as key providers of reef structure but also as recorders of past environmental change yet recent documented evidence of an unprecedented increase in the frequency of mortality in porites warrants investigation into the history of mortality and associated drivers to achieve this both an accurate chronology and an understanding of the life history strategies of porites are necessary sixty two individual uranium thorium u th dates from 50 dead massive porites colonies from the central inshore region of the great barrier reef gbr revealed the timing of mortality to have occurred predominantly over two main periods from 1989 2 4 1 to 2001 4 4 1 and from 2006 4 1 8 to 2008 4 2 2 a d with a small number of colonies dating earlier overall the peak ages of mortality are significantly correlated with maximum sea surface temperature anomalies despite potential sampling bias the frequency of mortality increased dramatically post 1980 these observations are similar to the results reported for the southern south china sea high resolution measurements of sr ca and mg ca obtained from a well preserved sample that died in 1994 6 2 3 revealed that the time of death occurred at the peak of sea surface temperatures sst during the austral summer in contrast sr ca and mg ca analysis in two colonies dated to 2006 9 3 0 and 2008 3 2 0 suggest that both died after the austral winter an increase in sr ca ratios and the presence of low mg calcite cements as determined by sem and elemental ratio analysis in one of the colonies was attributed to stressful conditions that may have persisted for some time prior to mortality for both colonies however the timing of mortality coincides with the 4th and 6th largest flood events reported for the burdekin river in the past 60 years implying that factors associated with terrestrial runoff may have been responsible for mortality our results show that a combination of u th and elemental ratio geochemistry can potentially be used to precisely and accurately determine the timing and season of mortality in modern massive porites corals for reefs where long term monitoring data are absent the ability to reconstruct historical events in coral communities may prove useful to reef managers by providing some baseline knowledge on disturbance history and associated drivers 2014 elsevier ltd all rights reserved

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

electron spin resonance esr dating abstract esr dating has been systematically applied in earth sciences and archaeology since 1975 when ikeya dated a stalactite from the akiyoshi cave in japan in the meantime this new technique has been successfully applied to the dating of materials such as speleothems spring deposited travertines mollusc shells corals and tooth enamel the present research focuses on the dating of quartz which allows the age assessment of heated ceramics volcanic rocks intrafault material or windblown sediments esr dating is based on the measurement of the number of paramagnetic centers in a mineral these centers are generated by alpha beta and gamma radiation of the matural radioelements such as u th and k and have accumulated over time two parameters have to be determined the accumulated dose ad and the dose rate d to which the sample was exposed this review comprises three major parts a introduction into esr dating b application of the method and c appendices giving detailed description of dose rate calculation physical basis of electron spin resonance the esr spectrometer and esr lines the major emphasis lies on the outline of the application of esr dating this includes the discussion of the esr signals of the various materials sampling sample preparation and measurement techniques

tethyan mediterranean organic carbon rich sediments from mesozoic black shales to sapropels the jurassic to holocene record of black shale deposition in the tethys mediterranean region is unrivalled by that of any other ocean basin either in land sections or drill cores the term black shale is used here broadly for sediments with elevated organic carbon concentrations 1 including the pliocene to recent sapropels most of the black shales are devoid of benthonic organisms are laminated and were deposited in distinct rhythms during periods when the deep waters of the ocean basins were anoxic or dysoxic the tethyan black shale records have become essential in studies of the transfer of organic carbon into the sediment record and for astronomical tuning and geological time scales these records have been central in understanding climate control on ocean dynamics and biogeochemical cycles the mesozoic black shales were deposited within well defined time envelopes of around 0 5 to 1 myr these black shales which were confined to certain chronostratigraphic intervals in the jurassic and cretaceous were recognized as expressions of global oceanic anoxic events in the mid 1970s and subsequently named after prominent researchers bonarelli selli goguel the black shale episodes were dated by biostratigraphic methods and by high resolution chemostratigraphy and cyclostratigraphy mesozoic black shales are now interpreted as the oceanographic expression of major perturbations of the global carbon cycle and climate research into younger pliocene to pleistocene sedimentary cycles including black shales termed sapropels exposed in land sections or found in pelagic and hemipelagic marine sediment cores of late quaternary age started in the 1950s main threads pursued from this end of the record were the climatic control of oceanic processes that permitted the development of highly detailed and precise time scales tuned to the astronomical clock of insolation changes palaeoclimate evolution of the circum mediterranean area and biogeochemical dynamics in anoxic basins after 50 years of intensive research the tethyan and mediterranean black shales remain subjects of fascination in earth science tracing the origins and building upon recent progress the current hypotheses on their formation are reviewed here it is a panorama of complex interplays between global and regional tectonics climate dynamics during both ice house and greenhouse states of global and regional climate oceanographic responses to these climate changes and biogeochemical adaptations that were all needed to shape an extraordinary archive of global change in the absence of human activity

esr and u series analyses on corals from huon peninsula new guinea ten coral samples from huon peninsula were selected for an esr and alpha spectrometric u series dating comparison th and u isotopes of seven esr samples were also analyzed by mass spectrometry it was found that the dose response of the paramagnetic centre at g 2 0007 is not strictly exponential but defect creation can be observed the comparison of the results shows considerable discrepancies between all three techniques but also inconsistencies between the results of the radiometric dating study with the assumed geological position of the samples problems of esr seem to lie in ad estimation and problems of u series dating in open system behaviour of the samples the study implies that samples have to be very carefully selected in order to perform a meaningful dating comparison

shore platform development on an uplifting limestone island over multiple sea level cycles niue south pacific abstract niue is an uplifted limestone island which preserves an atoll morphology with a sequence of terraces around its outer margin a modern terrace fringes much of the island and this paper examines the extent to which this terrace can be considered accretionary and constructed by coral and coralline algae or erosional and truncated by those processes that form shore platforms the occurrence of pleistocene limestone outcropping across this terrace and the continuation of caves and other karst features dissecting the sub aerial limestones onto the forereef indicate the overall significance of erosion at present live coral cover is restricted to isolated colonies growing in grooves potholes and karstic channels eroded into the modern terrace surface coralline algae coat the outer margin of this terrace and also veneer prominent surf benches that occur on the windward shore 1 2 m above the terrace surface terrace evolution on niue therefore appears to be primarily erosional in origin there is little accommodation space for reef growth and as a result accretional fringing reefs are absent around most of the island erosional processes have also dominated landscape evolution for at least the past few eustatic cycles fringing reef growth is absent or severely restricted during the last interglacial and occurs as sporadic small reefs on the seaward margin of an erosional terrace during the penultimate interglacial the development of terrace features in uplifting reef settings does not necessarily originate through accretional reef processes and may in fact be entirely erosional although reef terraces are frequently depositional in other settings those present on niue indicate a predominance of erosion indicating the need to discriminate emergent terraces in terms of the extent to which they are erosional or accretionary when using such features to reconstruct island palaeoenvironments

global sea level fluctuations during the last interglaciation mis 5e the geomorphology and morphostratigraphy of numerous worldwide sites reveal the relative movements of sea level during the peak of the last interglaciation marine isotope stage mis 5e assumed average duration between 13072 and 11972 ka because sea level was higher than present deposits are emergent exposed and widespread on many stable coastlines correlation with mis 5e is facilitated by similar morphostratigraphic relationships a low degree of diagenesis uranium thorium u th ages and a global set of amino acid racemization aar data this study integrates information from a large number of sites from tectonically stable areas including bermuda bahamas and western australia and some that have experienced minor uplift 2 5 m 100 ka including selected sites from the mediterranean and hawaii significant fluctuations during the highstand are evident at many mis 5e sites revealed from morphological stratigraphic and sedimentological evidence rounded and flat topped curves derived only from reef tracts are incomplete and not representative of the entire interglacial story despite predictions of much different sea level histories in bermuda the bahamas and western australia due to glacio and hydro isostatic effects the rocks from these sites reveal a nearly identical record during the last interglaciation the last interglacial highstand is characterized by several defined sea level intervals slis that include sli 1 post glacial mis 6 5e termination ii rise to above present before 130 ka sli 2 stability at 2 to 3 m for the initial several thousand years 130 to 125 ka during which fringing reefs were established and terrace morphology was imprinted along the coastlines sli 3 a brief fall to near or below present around 125 ka sli 4 a secondary rise to and through 3 4 m 124 to 122 ka followed by sli 5 a brief period of instability 120 ka characterized by a rapid rise to between 6 to 9 m during which multiple notches and benches were developed and sli 6 an apparently rapid descent of sea level into mis 5d after 119 ka u th ages are used to confirm the last interglacial age of the deposits but unfortunately in only two cases was it possible to corroborate the highstand subdivisions using radiometric ages sea levels above or at present were relatively stable during much of early mis 5e and the last 6 7 ka of mis 1 encouraging a comparison between them the geological evidence suggests that significant oceanographic and climatic changes occurred thereafter midway through and continuing through the end of mis 5e fluctuating sea levels and a catastrophic termination of mis 5e are linked to the instability of grounded and marine based ice sheets with the greenland gis and west antarctic wais ice sheets being the most likely contributors late mis 5e ice volume changes were accompanied by oceanographic reorganization and global ecological shifts and provide one ominous scenario for a greenhouse world r 2007 elsevier ltd all rights reserved

electron spin resonance esr dating in quaternary studies evolution recent advances and applications over the last few decades the importance of geochronology in quaternary studies has significantly increased and the development of accurate numerical dating tools has become an essential foundation for reliable interpretations of palaeoenvironmental proxies landscape evolution geomorphic processes palaeoclimate records palaeoecological changes archaeological histories and human evolution there is now a wide array of numerical quaternary dating methods available though their applicability and accuracy may vary significantly at individual sites depending on a series of factors including the age range of interest the types and purity of preserved material and its association e g taphonomic history stratigraphic correlation with the event that is being dated e g ludwig and renne 2000 grun et al 2010 rink and thompson 2015 rixhon et al 2017 radiometric methods such as radiocarbon argon argon ar ar and u series dating typically offer the greatest analytical precision and are based on relatively standardized analytical procedures other techniques such as electron spin resonance esr luminescence and cosmogenic radionuclide crn dating have not yet reached the same level of standardization but they nevertheless offer invaluable age constraint across a wide range of sites depositional contexts and timeframes particular when the more routinely used and standardized radiometric methods are not applicable

progress in esr dating of pleistocene corals a new approach for de determination abstract esr dating has been widely applied for dating of corals of the age up to 500 000 to 600 000 years ago many studies have yielded promising results but the accurate determination of the equivalent dose d e remains a major limitation inflexion points in the dose response curve are shown to hinder correct fitting and limit the reliability of d e values here we present a new approach to obtain more reliable d e values

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

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

evolution of tropical watersheds and continental hydrology during the late cretaceous greenhouse impact on marine carbon burial and possible implications for the future abstract regional climate modelling for the late cretaceous greenhouse and high resolution marine stratigraphic records from both sides of the low latitude atlantic show that tropical south american and african hydrology and watersheds had a strong effect on freshwater transfer into the equatorial atlantic and subsequently the marine carbon record this conclusion is derived from new detailed geochemical records from demerara rise off suriname drilled at ocean drilling program odp site 1261 combined with frequency analyses and climate simulations providing evidence for mainly eccentricity driven changes in carbon burial in the western tropical atlantic shorter orbital frequencies in particular precession clearly dominating black shale cycles off tropical africa odp site 959 are far less dominant at demerara rise despite comparable time resolution of the geochemical records we suggest that these different frequency patterns in carbon burial were related to the regional evolution of cretaceous watersheds and hydrology in tropical south america and africa river discharge deduced from simulations indicates higher and less variable discharge from south america compared to western africa at that time this runoff pattern would have supported more permanent anoxic conditions off south america compared to africa at least indirectly and caused the lack of strong higher frequency geochemical cycles in the western sector of the equatorial atlantic furthermore climate simulations show a general switch of primary runoff from either side of the cretaceous equatorial atlantic every half precession cycle i e every 10 kyr similarities between the developments of cretaceous and holocene hydrology in the tropical atlantic area imply that orbital scale evolution of watersheds is a robust feature through time that is independent from the mean global climate state based upon the comparison of cretaceous and holocene trends in hydrology we infer that future hydrology in the study region may develop in a comparable direction to the one observed in the cretaceous if true this suggests that the modern amazon rain forest could shrink over the next millennium due to a 30 loss of moisture while the congo rain forest in africa is likely to expand in response to a 14 gain in moisture

warm deep water ocean conveyor during cretaceous time because the deep water is associated with its high latitude sources a warm deep ocean durin gmesozoic cenozoi ctim ei sa challenge ther ei sn ofeasibl ephysica lmechanism that could maintain warm subpolar surface oceans in both hemispheres the goal of this study is to explore a hypothesis that a warm deep ocean can coexist with relatively cool subpolar high latitude sea surface in one hemisphere and a warmer subpolar sea surface in the other a series of numerical ocean circulation experiments confirms that the ocean meridional circulation can keep the abyssal ocean warm despite the northern subpolar surface water staying relatively cool

the quantification of breakwater armour profiles for design purposes abstract a new approach for the evaluation of block shape effects in both artificial and rock armour layers is proposed topographic profiles based on high resolution sampling frequencies of between 10 and 20 heights per nominal armour block width are considered model surfaces of a glass spheres and b rock aggregate were prepared and examined by topographic profile sampling a preliminary set of 15 statistical parameters or roughness descriptors were evaluated for each of 10 sets of profile height data a statistical comparison between the surfaces of models a and b indicates the potential of roughness descriptors such as mean peak curvature and peak density to discriminate between surfaces generated from blocks of different shapes filtering of height data for discrimination enhancement is also illustrated nomenclature is introduced to distinguish the planar orientations of the principal profiles of the breakwater the ac plane cross cuts the long axis and is the plane observed in the well known studies of s shaped profiles the bc and bd planes parallel the axis and are the planes proposed for analysis it is argued that the new monitoring method of topographic profile sampling and roughness descriptor analysis provides a promising additional means of assessing the relationship between block shape and hydraulic stability for model and prototype armour layers the importance of further development and testing of these techniques for the quantitative evaluation of surface geometry is stressed in view of the many possible future applications of these methods

high latitude salinity effects and interhemispheric thermohaline circulations a general circulation model for the ocean is used to investigate the interaction between the global scale thermohaline circulation and the salinity distribution it is shown that an equatorially asymmetric circulation can be maintained even under equatorially symmetric basin geometry and surface forcing multiple equilibrium solutions are obtained for the same forcing by perturbing the high latitude salinity field in an otherwise equatorially symmetric initial condition the timescale of the transition from the symmetric circulation to an asymmetric circulation depends critically on the sign of the initial salinity perturbation

causes and consequences of extreme permo triassic warming to globally equable climate and relation to the permo triassic extinction and recovery permian waning of the low latitude alleghenian variscan hercynian orogenesis led to a long collisional orogeny gap that cut down the availability of chemically weatherable fresh silicate rock resulting in a high co2 atmosphere and global warming the correspondingly reduced delivery of nutrients to the biosphere caused further increases in co2 and warming melting of polar ice curtailed sinking of o2 and nutrient rich cold brines while pole to equator thermal gradients weakened wind shear and associated wind driven upwelling lessened further diminishing productivity and carbon burial as the earth warmed dry climates expanded to mid latitudes causing latitudinal expansion of the ferrel circulation cell at the expense of the polar cell increased coastal evaporation generated o2 and nutrient deficient warm saline bottom water wsbw and delivered it to a weakly circulating deep ocean warm deep currents delivered ever more heat to high latitudes until polar sinking of cold water was replaced by upwelling wsbw with the loss of polar sinking the ocean was rapidly filled with wsbw that became increasingly anoxic and finally euxinic by the end of the permian rapid incursion of wsbw could have produced 20 m of thermal expansion of the oceans generating the well documented marine transgression that flooded embayments in dry hot pangaean mid latitudes the flooding further increased wsbw production and anoxia and brought that anoxic water onto the shelves release of co2 from the siberian traps and methane from clathrates below the warming ocean bottom sharply enhanced the already strong greenhouse increasingly frequent and powerful cyclonic storms mined upwelling high latitude heat and released it to the atmosphere that heat trapped by overlying clouds of its own making suggests complete breakdown of the dry polar cell resulting rapid and intense polar warming caused or contributed to extinction of the remaining latest permian coal forests that could not migrate any farther poleward because of light limitations loss of water stored by the forests led to aquifer drainage adding another 5 m to the transgression non peat forming vegetation survived at the newly moist poles climate feedback from the coal forest extinction further intensified warmth contributing to delayed biotic recovery that generally did not begin until mid triassic but appears to have resumed first at high latitudes late in the early triassic current quantitative models fail to generate high latitude warmth and so do not produce the chain of events we outline in this paper future quantitative modeling addressing factors such as polar cloudiness increased poleward heat transport by deep water and its upwelling by cyclonic storms and sustainable mid latitude sinking of warm brines to promote anoxia warming and thermal expansion of deep water may more closely simulate conditions indicated by geological and paleontological data

possible role of oceanic heat transport in early eocene climate increased oceanic heat transport has often been cited as a means of maintaining warm high latitude surface temperatures in many intervals of the geologic past including the early eocene although the excess amount of oceanic heat transport required by warm high latitude sea surface temperatures can be calculated empirically determining how additional oceanic heat transport would take place has yet to be accomplished that the mechanisms of enhanced poleward oceanic heat transport remain undefined in paleoclimate reconstructions is an important point that is often overlooked using early eocene climate as an example we consider various ways to produce enhanced poleward heat transport and latitudinal energy redistribution of the sign and magnitude required by interpreted early eocene conditions our interpolation of early eocene paleotemperature data indicate that an approximately 30 increase in poleward heat transport would be required to maintain eocene high latitude temperatures this increased heat transport appears difficult to accomplish by any means of ocean circulation if we use present ocean circulation characteristics to evaluate early eocene rates either oceanic processes were very different from those of the present to produce the early eocene climate conditions or oceanic heat transport was not the primary cause of that climate we believe that atmospheric processes with contributions from other factors such as clouds were the most likely primary cause of early eocene climate

investigation of thallium fluxes from subaerial volcanism implications for the present and past mass balance of thallium in the oceans abstract a suite of 34 volcanic gas condensates and particulates from kilauea hawaii mt etna and vulcano italy mt merapi indonesia white island and mt nguaruhoe new zealand were analysed for both tl isotope compositions and tl pb ratios when considered together with published tl pb abundance data the measurements provide globally representative best estimates of tl pb 0 46 0 25 and e 205 tl 1 7 2 0 for the emissions of subaerial volcanism to the atmosphere and oceans e 205 tl is the deviation of the 205 tl 203 tl isotope ratio from nist srm 997 isotope standard in parts per 10 000 compared to igneous rocks of the crust and mantle volcanic gases were found to have i tl pb ratios that are typically about an order of magnitude higher and ii significantly more variable tl isotope compositions but a mean e 205 tl value that is indistinguishable from estimates for the earth s mantle and continental crust the first observation can be explained by the more volatile nature of tl compared to pb during the production of volcanic gases whilst the second reflects the contrasting and approximately balanced isotope fractionation effects that are generated by partial evaporation of tl during magma degassing and partial tl condensation as a result of the cooling and differentiation of volcanic gases mass balance calculations based on results from this and other recent tl isotope studies were carried out to investigate whether temporal changes in the volcanic tl fluxes could be responsible for the dramatic shift in the e 205 tl value of the oceans at 55 ma which has been inferred from tl isotope time series data for ferromanganese crusts the calculations demonstrate that even large changes in the marine tl input fluxes from volcanism and other sources are unable to significantly alter the tl isotope composition of the oceans based on modelling it is shown that the large inferred change in the e 205 tl value of seawater is best explained if the oceans of the early cenozoic featured significantly larger tl output fluxes to oxic pelagic sediments whilst the sink fluxes to altered ocean crust remained approximately constant

stability of rubble mound slopes under random wave attack the objective of the present research project is to give new practical design formulae for rubble mound slopes under random wave attack the study is based upon a series of model tests more than two hundred tests have been performed in order to vary systematically all the relevant variables the main shortcomings in hudson type formulae have been solved as a result of the present series of investigations stability formulae are given which include the influence of wave period number of waves armour grading spectrum shape groupiness of waves and the permeability of the core

a comparison of eocene climate model results to quantified paleoclimatic interpretations abstract the integration of climate model results and geologic information offers considerable potential for deriving greater insight into the geologic record in this study climate model results and quantified climatic interpretations derived from proxy data are compared to assess model capabilities and to examine proxy data interpretations atmospheric general circulation model experiments were used to produce a range of possible representative eocene climate states based on current knowledge of the eocene record the climate model experiments incorporate two idealized endmembers of eocene ocean surface temperature distributions characterized by very different latitudinal gradients model results are compared to quantified interpretations of the climate of early eocene north america in an attempt to identify one of the sea surface temperature distributions as more likely to have existed during the eocene the comparisons do not produce a conclusive match between inferred paleoclimatic information and any single case of model results but some interesting insights become apparent model predictions of mean annual temperature and mean annual precipitation compare favorably to interpretations from geologic evidence but there are large differences between model results and interpreted paleoclimatic parameters of minimum surface temperature and mean annual temperature range several possible causes for these differences are discussed

esr ages of middle pleistocene corals from the ryukyu islands abstract electron spin resonance ages of 11 corals from the lower part of the ryukyu group japan can be classified into two groups about 600 000 and 800 000 yr the result indicates that the lower part of the ryukyu group is correlated to at least two of the oxygen isotope stages 15 17 19 21 and 23 lowermost part of the ryukyu group was probably deposited during a large transgression and may be correlated worldwide

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

response of late ordovician paleoceanography to changes in sea level continental drift and atmospheric pco2 potential causes for long term cooling and glaciation abstract we performed sensitivity experiments using an ocean general circulation model at two stages of the late ordovician caradoc 454 ma ashgill 446 ma under a range of atmospheric pco2 values 8 18 pal pre industrial atmospheric level at high and low sea level the model results indicate that the long term cooling trend during the late ordovician can be explained by progressive cooling of the global ocean in response to falling levels of atmospheric pco2 sea level change and paleogeographic change these results also explain the occurrence of low latitude cool water carbonates in north america in all simulations a drop in sea level led to a reduction in poleward ocean heat transport this indicates a possible positive feedback that could have enhanced global cooling in response to sea level drop during the late ordovician alterations in poleward ocean heat transport linked to changes of atmospheric pco2 also indicate that there is a threshold of 10 pal above which ocean current change cannot be responsible for glaciation in the late ordovician continental drift could explain the observed global cooling trend in the late ordovician through a combined poleward ocean heat transport feedback and increased ice albedo effect if atmospheric pco2 was low during the entire late ordovician the model results further indicate that the response of meridional overturning to changes in paleogeography atmospheric pco2 and sea level is stronger than the response of surface circulation to these perturbations because the overturning circulation is so strong meridional overturning was the dominant mechanism for described changes in heat transport in the late ordovician

comparisons of esr ages of corals using different signals at x and q band re examinations of corals from huon peninsula papua new guinea abstract esr ages of corals were compared to assess the validity of different dating techniques ten coral samples from the huon peninsula of north eastern papua new guinea previously dated by alpha spectrometric and mass spectrometric uranium series methods grun et al 1992 omura et al 1994 were selected for investigation the esr spectra were recorded at x and q band before and after annealing at 150 c for 14 h with low and high microwave powers the d e values based on the g 2 0007 signal were not significantly affected by microwave power and preheating treatment the d e values based on the g 2 0058 signal after annealing appear to be comparable to those based on the g 2 0007 signal and both sets of corresponding esr ages are broadly in agreement with the uranium series ages

esr dating of corals abstract the ages of 24 coral samples from barbados and the new hebrides were determined simultaneously by esr and another independent dating method and ms u series and 14 c all parameters for esr dating were determined without cross calibration with another dating method including thermal stability and effective efficiency the results show a relatively good concordance furthermore a systematic esr dating study on the reef tracts of barbados 83 samples revealed satisfactory agreement between esr and u series data whereas previously published he u data seemed to show open system behaviour the thermal stability of the esr signal at g 2 0007 0 0002 estimated to be in the range of 500 ka does not seem to have an apparent influence on the esr results

cenomanian palaeotemperatures derived from the oxygen isotopic composition of brachiopods and belemnites evaluation of cretaceous palaeotemperature proxies sixty low magnesium calcite samples from cenomanian articulate brachiopods belemnites and oysters from the epicontinental shelf sea of europe were geochemically and microscopically studied in order to evaluate their preservation and potential as carriers of palaeoenvironmental information the sampled localities in northern spain germany and southern england cover the transition between subtropical 25 30 n and temperate 33 38 n climates mean cenomanian salinity adjusted palaeotemperatures of diagenetically unaltered terebratulid and rhynchonellid brachiopods are 25 5 1 3 c in spain and 19 4 1 9 c in southern england the resulting low to mid latitude meridional temperature gradient of 0 7 c per degree latitude is similar to the gradient today and suggests modern heat transport values for cenomanian low latitudes oxygen isotopic composition of unaltered specimens of the upper cenomanian belemnite praeactinocamax plenus mean 0 2 is enriched in 18o by 1 in comparison to brachiopod shells correspondingly upper cenomanian palaeotemperatures derived from belemnite calcite 13 0 1 3 c underestimate modelled mid latitude sea surface temperatures by 6 c since p plenus occurs as boreal pulse fauna during a short interval in the late cenomanian its heavy oxygen isotopic composition can be attributed either to migration from a cooler and or deeper water mass or to unknown vital effects