bipolar seesaw control on last interglacial sea level our current understanding of ocean atmosphere cryosphere interactions at ice age terminations relies largely on assessments of the most recent last glacial interglacial transition1 2 3 termination i t i but the extent to which t i is representative of previous terminations remains unclear testing the consistency of termination processes requires comparison of time series of critical climate parameters with detailed absolute and relative age control however such age control has been lacking for even the penultimate glacial termination t ii which culminated in a sea level highstand during the last interglacial period that was several metres above present4 here we show that heinrich stadial 11 hs11 a prominent north atlantic cold episode5 6 occurred between 135 1 and 130 2 thousand years ago and was linked with rapid sea level rise during t ii our conclusions are based on new and existing6 7 8 9 data for t ii and the last interglacial that we collate onto a single radiometrically constrained chronology the hs11 cold episode5 6 punctuated t ii and coincided directly with a major deglacial meltwater pulse which predominantly entered the north atlantic ocean and accounted for about 70 per cent of the glacial interglacial sea level rise8 9 we conclude that possibly in response to stronger insolation and co2 forcing earlier in t ii the relationship between climate and ice volume changes differed fundamentally from that of t i in t i the major sea level rise clearly post dates3 10 11 heinrich stadial 1 we also find that hs11 coincided with sustained antarctic warming probably through a bipolar seesaw temperature response12 and propose that this heat gain at high southern latitudes promoted antarctic ice sheet melting that fuelled the last interglacial sea level peak

the evolution of mid paleocene early eocene coral communities how to survive during rapid global warming abstract today diverse communities of zooxanthellate corals thrive but do not build reef under a wide range of environmental conditions in these settings they inhabit natural bottom communities sometimes forming patch reefs coral carpets and knobs episodes in the fossil record characterized by limited coral reef development but widespread occurrence of coral bearing carbonates may represent the fossil analogs of these non reef building zooxanthellate coral communities if so the study of these corals could have valuable implications for paleoenvironmental reconstructions here we focus on the evolution of early paleogene corals as a fossil example of coral communities mainly composed by zooxanthellate corals or likely zooxanthellate commonly occurring within carbonate biofacies and with relatively high diversity but with a limited bioconstructional potential as testified by the reduced record of coral reefs we correlate changes of bioconstructional potential and community compositions of these fossil corals with the main ecological environmental conditions at that time the early paleogene greenhouse climate was characterized by relatively short pulses of warming with the most prominent occurring at the paleocene eocene boundary petm event associated with high weathering rates nutrient fluxes and pco 2 levels a synthesis of coral occurrences integrated with our data from the adriatic carbonate platform sw slovenia and the minervois region sw france provides evidence for temporal changes in the reef building capacity of corals associated with a shift in community composition toward forms adapted to tolerate deteriorating sea water conditions during the middle paleocene coral algal patch reefs and barrier reefs occurred from shallow water settings locally with reef crest structures a first shift can be traced from middle paleocene to late paleocene with small coral algal patch reefs and coral bearing mounds development in shallow to intermediate water depths in these mounds corals were highly subordinated as bioconstructors to other groups tolerant to higher levels of trophic resources calcareous red algae encrusting foraminifera microbes and sponges a second shift occurred at the onset of the early eocene with a further reduction of coral framework building capacity these coral communities mainly formed knobs in shallow water turbid settings associated with abundant foraminiferal deposits we suggest that environmental conditions other than high temperature determined a combination of interrelated stressors that limited the coral reef construction a continuous enhancement of sediment load nutrients combined with geochemical changes of ocean waters likely displaced corals as the main bioconstructors during the late paleocene early eocene times nonetheless these conditions did not affect the capacity of some corals to colonize the substrate maintain biodiversity and act as locally important carbonate sediment producers suggesting broad environmental tolerance limits of various species of corals the implications of this study include clues as to how both ancient and modern zooxanthellate corals could respond to changing climate

patterns of accretion of reefs in the sudanese red sea abstract reefs in the north towartit and shambaya groups of the sudanese red sea rest on major blocks which have been defined by large scale fault movements the dominant surface features in these areas have been formed by the sub aerial sculpting of tertiary and later limestones during late pleistocene periods of low sea level stand this has resulted in the formation of large numbers of closed depressions reaching 30 m depth these punctuate a surface lying between 20 and 30 m which is itself probably a residual of an older undulating higher level surface the margins of depressions are submarine cliffs the smooth floors are blanketted with recent sediments while the intervening ridges have become the sites for reef accretion present coral growth began about 6000 years ago and has reached a thickness of 10 to 20 m it has been limited in deeper water but in shallower areas may have been aided by establishment on existing pinnacles steep margins occur on both the windward baraja and leeward towartit harvey margins of reefs these may result from inequalities of growth but cannot be directly related to environmental energy windward and leeward shores are characterised by contrasted coral associations a windward acropora association and a leeward porites association this distribution reflects a depletion of resources downcurrent rather than major differences in water movement reef edges are the most important sediment generating zones and patterns of dispersal point to a dominant westward downwind movement 50 80 of sediments coarser than 1 o are coral and algal fragments mollusc shells are a minor component but reach 26 on the towartit fringe homotrema benthic forams bryozoa crustacean and echinoderm fragments rarely rise above a few percent each mean sizes of sediments range from 2 3167 to 1 2333 o with the coarsest close to the reef edges and the finest in deep water or down current most are poorly sorted and values for standard deviation range between 2 1714 and 0 9512 o skewness values indicate symmetrical or coarse skewed distributions 0 0132 to 0 4982 finally figures for normalised kurtosis range between 0 6023 and 0 4532 these suggest that sediments consist of at least two sub populations 1 a base stock generated in the edge zone with characteristics varying systematically down current and 2 grains formed within the transport system with characters owing more to ecological factors than hydrodynamics the irregular mixing of these two accounts for the variation shown in conclusion the character of the reefs depends both upon present day processes and an inherited morphology

an 800 kyr record of global surface ocean δ18o and implications for ice volume temperature coupling abstract the sequence of feedbacks that characterized 100 kyr glacial cycles of the past million years remains uncertain hampering an understanding of the interconnections between insolation ice sheets greenhouse gas forcing and climate critical to addressing this issue is an accurate interpretation of the marine 18 o record the main template for the ice ages this study uses a global compilation of 49 paired sea surface temperature planktonic 18 o records to extract the mean 18 o of surface ocean seawater over the past 800 kyr which we interpret to dominantly reflect global ice volume the results indicate that global surface temperature inferred deep ocean temperature and atmospheric co2 decrease early during each glacial cycle in close association with one another whereas major ice sheet growth occurs later in glacial cycles these relationships suggest that ice volume may have exhibited a threshold response to global cooling and that global deglaciations do not occur until after the growth of large ice sheets this phase sequence also suggests that the ice sheets had relatively little feedback on global cooling simple modeling shows that the rate of ice volume change through time is largely determined by the combined influence of insolation temperature and ice sheet size with possible implications for the evolution of glacial cycles over the past three million years

abrupt change of antarctic moisture origin at the end of termination ii the deuterium excess of polar ice cores documents past changes in evaporation conditions and moisture origin new data obtained from the european project for ice coring in antarctica dome c east antarctic ice core provide new insights on the sequence of events involved in termination ii the transition between the penultimate glacial and interglacial periods this termination is marked by a north south seesaw behavior with first a slow methane concentration rise associated with a strong antarctic temperature warming and a slow deuterium excess rise this first step is followed by an abrupt north atlantic warming an abrupt resumption of the east asian summer monsoon a sharp methane rise and a co 2 overshoot which coincide within dating uncertainties with the end of antarctic optimum here we show that this second phase is marked by a very sharp dome c centennial deuterium excess rise revealing abrupt reorganization of atmospheric circulation in the southern indian ocean sector

global ocean heat content in the last interglacial the last interglacial 129 116 thousand years ago ka represents one of the warmest climate intervals of the past 800 000 years and the most recent time when sea level was metres higher than today however the timing and magnitude of the peak warmth varies between reconstructions and the relative importance of individual sources that contribute to the elevated sea level mass gain versus seawater expansion during the last interglacial remains uncertain here we present the first mean ocean temperature record for this interval from noble gas measurements in ice cores and constrain the thermal expansion contribution to sea level mean ocean temperature reached its maximum value of 1 1 0 3 c warmer than modern values at the end of the penultimate deglaciation at 129 ka which resulted in 0 7 0 3 m of thermosteric sea level rise relative to present level however this maximum in ocean heat content was a transient feature mean ocean temperature decreased in the first several thousand years of the interglacial and achieved a stable comparable to modern value by 127 ka the synchroneity of the peak in mean ocean temperature with proxy records of abrupt transitions in the oceanic and atmospheric circulation suggests that the mean ocean temperature maximum is related to the accumulation of heat in the ocean interior during the preceding period of reduced overturning circulation rapid oceanic and atmospheric circulation shifts led to a transient peak in the mean temperature of the ocean at the start of the last interglacial according to noble gas isotope records from an antarctic ice core

sequential evolution and diagenesis of pleistocene coral reefs south sinai egypt abstract the uplifted pleistocene coral reefs in south sinai represent two major depositional sequences they generally form two morphological terraces which locally are tilted and offset by still active faulting the major reef sequences are composed of several small scale sequences corals grew rapidly when accommodation space was created by eustatic sea level rise or fault block subsidence as the accommodation decreased coral rubble and siliciclastic sands prograded over reefal and lagoonal sediments thus creating a shallowing upward sequence terrigenous input was further stimulated by a more humid climate during interglacial times 230 th 234 u dating places the older reef cycle between 350 000 and 270 000 years b p which corresponds to the interglacial period of isotope stage 9 the younger reef cycle has been dated between 140 000 and 60 000 years b p isotope stage 5 an intermediate relic sequence found in only one outcrop can be attributed to isotope stage 7 correlation of the small scale sequences is difficult age dating is not precise enough and local tectonic activity in many cases overruled the smaller eustatic fluctuations the younger reef sequence commonly exhibits marine cements whereas the older sequence was exposed to freshwater dissolution and cementation an important feature is the locally pervasive dolomitization especially of the older reef oxygen and carbon isotope values suggest that the dolomite formed in a seawater dominated mixing zone multiple phases of dissolution cementation and dolomitization point to a very complex diagenetic history

siluro devonian alpine reefs and pavements palaeozoic sediments of austria are separated by the periadriatic fault into eastern alpine upper middle and lower austroalpine and southern alpine units we herein present six case studies showing up the different development of shallow marine communities with special regard to carbonate factories and shell pavements occurring in both regions during the siluro devonian time span upper silurian upper devonian deposits of the eastern alps comprise accumulations of serpulid tubes southern burgenland and septatrypa pavements amphipora mounds coral stromatoporoid biostromes and stachyodes auloporoid beds regarded as pioneer reef communities graz palaeozoic respectively lower silurian strata of the southern alps consist of pelagic sediments persisting to the upper silurian and therefore differ from contemporaneous successions in the eastern alps intercalated in ludlow orthocerid limestone beds cardiola pavements appear carnic alps within the lower devonian sequence mounds were built by baffling calcareous algae and tabulozoan communities coral stromatoporoid patch reefs occur during the pragian givetian and frasnian stages investigation of silurian upper devonian reefs and reef related successions within austria s borders has a long tradition a survey of these developments is compiled in a stratigraphic scheme representing all non metamorphic units of austria generally all palaeozoic strata suffered differing post depositional destruction i e tectonic splitting dolomitization metamorphic overprint etc during variscan and alpidic orogenesis thus complicating or limiting to some respect their investigation from southern burgenland the graz palaeozoic the carnic alps and the karawanken mountains reefs which cover a time segment of some 55 ma are presented in overview stratigraphical framework of dismembered

synchronous deglacial overturning and water mass source changes understanding changes in ocean circulation during the last deglaciation is crucial to unraveling the dynamics of glacial interglacial and millennial climate shifts we used neodymium isotope measurements on postdepositional iron manganese oxide coatings precipitated on planktonic foraminifera to reconstruct changes in the bottom water source of the deep western north atlantic at the bermuda rise comparison of our deep water source record with overturning strength proxies shows that both the deep water mass source and the overturning rate shifted rapidly and synchronously during the last deglacial transition in contrast any freshwater perturbation caused by heinrich event 1 could have only affected shallow overturning these findings show how changes in upper ocean overturning associated with millennial scale events differ from those associated with whole ocean deglacial climate events

ice shelf collapse from subsurface warming as a trigger for heinrich events episodic iceberg discharge events from the hudson strait ice stream hsis of the laurentide ice sheet referred to as heinrich events are commonly attributed to internal ice sheet instabilities but their systematic occurrence at the culmination of a large reduction in the atlantic meridional overturning circulation amoc indicates a climate control we report mg ca data on benthic foraminifera from an intermediate depth site in the northwest atlantic and results from a climate model simulation that reveal basin wide subsurface warming at the same time as large reductions in the amoc with temperature increasing by approximately 2 c over a 1 2 kyr interval prior to a heinrich event in simulations with an ocean model coupled to a thermodynamically active ice shelf the increase in subsurface temperature increases basal melt rate under an ice shelf fronting the hsis by a factor of approximately 6 by analogy with recent observations in antarctica the resulting ice shelf loss and attendant hsis acceleration would produce a heinrich event

radiometric 81kr dating identifies 120 000 year old ice at taylor glacier antarctica we present successful 81kr kr radiometric dating of ancient polar ice krypton was extracted from the air bubbles in four 350 kg polar ice samples from taylor glacier in the mcmurdo dry valleys antarctica and dated using atom trap trace analysis atta the 81kr radiometric ages agree with independent age estimates obtained from stratigraphic dating techniques with a mean absolute age offset of 6 2 5 ka our experimental methods and sampling strategy are validated by i 85kr and 39ar analyses that show the samples to be free of modern air contamination and ii air content measurements that show the ice did not experience gas loss we estimate the error in the 81kr ages due to past geomagnetic variability to be below 3 ka we show that ice from the previous interglacial period marine isotope stage 5e 130 115 ka before present can be found in abundance near the surface of taylor glacier our study paves the way for reliable radiometric dating of ancient ice in blue ice areas and margin sites where large samples are available greatly enhancing their scientific value as archives of old ice and meteorites at present atta 81kr analysis requires a 40 80 kg ice sample as sample requirements continue to decrease 81kr dating of ice cores is a future possibility

800 000 years of abrupt climate variability we constructed an 800 000 year synthetic record of greenland climate variability based on the thermal bipolar seesaw model our greenland analog reproduces much of the variability seen in the greenland ice cores over the past 100 000 years the synthetic record shows strong similarity with the absolutely dated speleothem record from china allowing us to place ice core records within an absolute timeframe for the past 400 000 years hence it provides both a stratigraphic reference and a conceptual basis for assessing the long term evolution of millennial scale variability and its potential role in climate change at longer time scales indeed we provide evidence for a ubiquitous association between bipolar seesaw oscillations and glacial terminations throughout the middle to late pleistocene

remote sensing of geomorphology and facies patterns on a modern carbonate ramp arabian gulf dubai u a e abstract the occurrence of power law relationships in the spatial distribution of sedimentary lithotopes has been identified in both modern and ancient carbonate depositional bodies in this study facies patterns and their spatial relationships are investigated quantitatively in an arabian gulf shallow subtidal carbonate ramp setting using a synergy of ikonos satellite imagery and vessel based acoustic bathymetry survey three dimensional reconstruction of the facies distribution on the seabed enabled quantification of relationships between eight dominant facies classes and the association of particular lithotopes to water depth fractal behavior was investigated using a combination of boundary and patch based metrics and the spatial distribution of early diagenetically cemented hardgrounds and unconsolidated carbonate sand were shown to display strong fractal properties in contrast we show that landscape scale processes can be treated as essentially deterministic and facies neighborhood patterns are strongly probabilistic identifying that the heterogeneity of shallow subtidal carbonate facies scales with a power law within certain thresholds has the potential to serve as a tool in environmental reconstruction in the ancient where information on the lateral persistence of facies units is difficult to obtain the findings are relevant to the interpretation of stratigraphic sequences and paleo depth analysis

reservoir scale heterogeneity in depositional packages and diagenetic patterns on a reef rimmed platform upper miocene mallorca spain predictive models for interwell scale variations in heterogeneous carbonate rock are best made from outcrop studies of well exposed limestone and dolomite such as the upper miocene reef complex that crops out in the sea cliffs of mallorca spain the sea cliff sections reveal highly complex lithofacies stacking patterns that could lead to ambiguous lateral correlations of coeval units the stratigraphic complexity and distribution of primary and secondary porosity are the result of a sea level driven hierarchical stacking of different magnitudes of accretional units thickest sections of porous and permeable rocks are in the aggradational portions of the reef upper slope and outer lagoon units the relative volume of the various accretional units and heterogeneity in the lithofacies architecture were dependent on the amount of carbonate production which was related to 1 accommodation changes controlled by sea level fluctuations and 2 depositional profile moldic porosity mostly from the dissolution of aragonitic constituents is the predominant porosity type and its heterogeneous distribution is related to the lateral and vertical distribution of lithofacies the secondary porosity in much of this reef complex was produced mainly during early dolomitization dolomite patterns are complicated apparently mainly related to shallow flooding of the platform during third or fourth order sea level highs and to geographic location of permeable pathways for brine reflux probably primarily through fourth order aggradational reef units many of these stratigraphic complexities and diagenetic patterns are below the resolution of seismic and well analyses thus models based on outcrop data such as this can enhance reservoir development in certain shallow water carbonate rocks

coral reef records of quaternary changes in climate and sea level abstract although coral reefs have long been regarded as documenting climate change largely through its effects on sea level the temporal continuity and sensitivity to disturbance of their records appears to fall short of those provided by ice cores deep sea sediments and similar proxies the reasons for this anomaly relate principally to shifts in the loci of deposition the temporal windows in which accretion has been able to occur in a given place reflecting sea level at a particular height relative to the present datum are severely constrained where it has been possible coral growth and reef accretion have been and are sensitive to the signals provided by the environment in the form of changes in water depth temperature salinity nutrient supply turbidity and ph acidity concomitant with changes in sea level itself changes in these environmental parameters are directly or indirectly controlled by climate however because the responses of corals to stimuli are commonly site specific and the nature of the changes evoked so disparate it is likely that only major sea level cycles will provide evidence of a consistent global response in what has been a segmented record

rudists as gregarious sediment dwellers not reef builders on cretaceous carbonate platforms abstract it has sometimes been claimed that rudist bivalves competitively displaced corals from reef frameworks during the cretaceous this hypothesis combines two assertions 1 that the autecology of rudists was convergent with that of reef building corals and 2 that rudist formations commonly developed as reefs we dispute both assertions and thus reject the hypothesis of competitive displacement we argue instead that mobile sediments rather than frameworks dominated the margins and tops of most of the extensive carbonate platforms of the period and that it was on these non reefal biotopes that the rudists flourished definitions of reefs tend to combine two major elements 1 a robust biogenic framework with accompanying sedimentary and diagenetic components and 2 topographical relief such definitions are clearly rooted in recent coral reefs in which endosymbiotic zooxanthellae permit the extensive growth of colonial coral frameworks in shallow but relatively nutrient poor waters coralline algae and cementation may contribute significantly to the growth of rigid structures and topography is largely the legacy of pleistocene changes in sea level in rudist formations in contrast individual rudist congregations are volumetrically limited relative to sediment they are often loosely constructed and they evidently showed little if any original relief tabular and small lenticular units predominate these differences in structure and palaeoenvironmental situation between rudist and modern coralgal associations reflect the different autecologies of the constituent organisms the clonal growth of corals predisposes them to the development of frameworks projecting above the sediment surface herein termed superstratal growth by contrast the aclonal development of rudists was better suited to the opportunistic occupation of a variety of temporarily available substrata by large numbers of individuals in particular elevator rudists in which the entire commissure exhibited upward growth evidently grew with their shells largely embedded in and supported by the ambient sediment herein termed constratal growth moreover the tolerances and growth responses of rudists to such factors as water turbidity nutrients and current regime were quite different from those of the majority of reef building corals despite repeated assertions in the literature that rudists possessed zooxanthellae only a few species show any evidence for such a symbiosis and other evidence suggests that most lacked them in view of these differences in their preferred biotopes competition between rudists and corals is doubtful even though members of both groups co occur in many areas the relative decline of coral frameworks in the cretaceous was thus probably independently caused

pliocene lower pleistocene shallow water mixed siliciclastics and carbonates yanigua and los haitises formations in eastern hispaniola dominican republic the virtually unfolded sedimentary cover of the cordilleras central and oriental in the eastern dominican republic eastern hispaniola tropical north atlantic largely consists of pliocene to early pleistocene mixed siliciclastics and carbonates these deposits have been grouped into two laterally interfingering mapping units the yanigua and los haitises formations the former mainly siliciclastics comprises marl marly limestone and minor conglomerate sandstone lignite and carbonaceous clay and crops out closest to the basement the los haitises formation mainly consists of limestone and intercalating beds of marly limestone and marl lithological mapping at the 1 50 000 scale and facies analysis of twelve measured sections and of additional fourteen outcrops suggest that these deposits mainly formed on a shallow water marine platform fringing the precursor reliefs of the cordillera oriental and the southeastern end of the cordillera central only a limited proportion of sediment formed in floodplains and marshes marl and marly limestone dominated the inner platform sediments terrigenous mud decreased away from the emergent basement and carbonate sedimentation dominated the more external platform corals molluscs echinoids foraminifers bryozoans coralline algae and halimeda are the main components with varying amounts of carbonate mud the platform was generally a low energy environment with seagrass patches in the inner platform corals grew as isolated colonies or as small patch reefs dominated by porites in marly and bioclastic substrates branching corals stylophora and acropora grew in extensive carpets in more distal areas at least in the last stage of its development early pleistocene the platform was rimmed by a reef barrier similar to the holocene caribbean barrier reefs with acropora gr palmata a cervicornis porites montastrea siderastrea and diploria as the main reef builders

response of reef coral communities to sea level rise a holocene model from mauritius western indian ocean the fringing reef at pointe au sable mauritius indian ocean was used to examine the effects of holocene sea level rise on coral growth this reef is about 1000 m wide and comprises a forereef slope 30 m maximum depth a narrow reef crest and a very shallow backreef 1 5 m maximum depth four major coral communities were recognized which developed within relatively narrow depth ranges a pachyseris oulophyllia community deeper than 20 m an acropora tabulate faviid community 20 6 m a robust branching acropora community less than 6 m and a pavona community less than 10m three high recovery cores show the holocene reef sequence is a maximum of 19 3 m thick and comprises four coral biofacies which are similar to counterparts identified in modern communities robust branching tabular branching robust branching domal and foliaceous coral facies a minimum sea level curve for the past 7500 years was constructed using distribution patterns of coral biofacies and radiocarbon dates from corals reconstruction of reef growth history indicates that both offshore and onshore reef zones were developing coevally aggrading at rates of 4 3 mm year 1 from 6900 years b p the reef caught up with sea level only after sea level stabilized changes in coral community and reef growth rates were driven principally by increasing water agitation due to the decrease in accommodation space based on the composition of the successive coral assemblages the reef appears to have grown through successive equilibrium stages

variations in pleistocene coral assemblages in space and time in southern and northern central ryukyu islands japan we studied the taxonomic and morphological compositions of pleistocene coral assemblages in 24 quadrats in okinawa jima southern central ryukyus and in 14 quadrats in kikai jima northern central ryukyus a total of 72 species belonging to 35 genera were identified in okinawa jima whereas 65 species coming under 33 genera were recorded in kikai jima cluster analysis of the bray curtis bc similarity coefficient produced 8 coral associations and 3 ungrouped taxa they correspond to a wide range of reef environments from shallow lagoon to lower reef slope settings the analysis of taxonomic similarities among quadrats leads to the identification of 7 clusters and 5 isolated quadrats the segregation of quadrats indicating a same reef zone into distinctive groups or single branches in the cluster diagram reflects the within reef slope variability in community structure specifically encrusting acropora palifera indicative of the upper reef slope zone shows a great variability of associated coral species and morphologies we also report differences in the geographic distribution of acropora palifera and platygyra contorta between present day and pleistocene reefs which may be linked to changes in sea surface temperature the decrease in the total species and generic richness recorded in modern reefs is not clearly detected in the fossil record in addition mds ordination of the bc similarities highlights patterns of reef zonation and geographic differences in taxonomic composition one way tests of similarity anosim show that differences in the composition of upper reef slope coral assemblages between okinawa jima and kikai jima are not larger than those observed between southern and central okinawa jima finally we report various types of coral successions sea level changes resulted in transitions from one reef zone to another whereas local disturbances are likely to have been responsible for the successions of distinctive coral assemblages with overlapping depth ranges which reflect the within reef zone variability

orbital and millennial antarctic climate variability over the past 800 000 years a high resolution deuterium profile is now available along the entire european project for ice coring in antarctica dome c ice core extending this climate record back to marine isotope stage 20 2 800 000 years ago experiments performed with an atmospheric general circulation model including water isotopes support its temperature interpretation we assessed the general correspondence between dansgaard oeschger events and their smoothed antarctic counterparts for this dome c record which reveals the presence of such features with similar amplitudes during previous glacial periods we suggest that the interplay between obliquity and precession accounts for the variable intensity of interglacial periods in ice core records

ice age terminations 230th dated oxygen isotope records of stalagmites from sanbao cave china characterize asian monsoon am precipitation through the ends of the third and fourthmost recent ice ages as a result am records for the past four glacial terminations can now be precisely correlated with those from ice cores and marine sediments establishing the timing and sequence of major events in all four cases observations are consistent with a classic northern hemisphere summer insolation intensity trigger for an initial retreat of northern ice sheets meltwater and icebergs entering the north atlantic alter oceanic and atmospheric circulation and associated fluxes of heat and carbon causing increases in atmospheric co2 and antarctic temperatures that drive the termination in the southern hemisphere increasing co2 and summer insolation drive recession of northern ice sheets with probable positive feedbacks between sea level and co2

gas records from the west greenland ice margin covering the last glacial termination a horizontal ice core abstract certain sites along ice sheet margins provide an easily accessible and almost unlimited supply of ancient ice at the surface measurements of gases in trapped air from ice outcropping at pakitsoq west greenland demonstrate that ancient air is mostly well preserved no alterations in 18 o atm and 15 n of n 2 are apparent and alterations in methane are found in only a few ice sections using measurements of these gases we have unambiguously identified a stratigraphic section containing ice from the end of last glacial period as well as bolling allerod younger dryas and preboreal intervals extensive sections of ice from the holocene and most ages within the last glacial period are probably also present very accurate dating has been possible in the ice section containing the younger dryas preboreal abrupt climate transition signal the ice at pakitsoq is folded and non uniformly thinned with many cross cutting bands of bubble free ice and dust the cross cutting features are associated with anomalies in both the gas and the ice records with careful sampling to avoid these the ice at pakitsoq is suitable for recovery of large volume samples of the ancient atmosphere for analysis of trace constituents such as 14 ch 4

the descriptive nomenclature and classification of growth fabrics in fossil scleractinian reefs abstract framework sensu stricto is a concept originally relating to modern reefs and is defined by structural ecological and sedimentological criteria however in the geological literature the term framework has come to be applied to almost any organically influenced in situ accumulation including non calcareous non rigid facies associated with sea grasses this drastic departure from the original meaning is misleading and scientifically unhelpful the concept of wave resistance is integral to that of framework but in the geological record it is not easy to evaluate and the term may be of little comparative use between reef environments it is suggested that the term growth fabric be generally applied as a descriptive term for the presence of aggregated in situ corals or other organisms in growth position within a facies the term growth fabric should be used as an alternative to framework as a purely descriptive term the term framework should be restricted to its original definition and used only where the criteria for framework can be clearly demonstrated two end member types of scleractinian growth fabric genesis are recognised termed superstratal and constratal terms adapted from gili e masse j p skelton p w 1995 rudists as gregarious sediment dwellers not reef builders on cretaceous carbonate platforms palaeogeogr palaeoclimatol palaeoecol 118 245 267 in a superstratal growth fabric the constituent organisms collectively projected decimetres to metres above the substratum creating positive topographic relief in contrast constratal growth is where vertical organic accretion occurred at a similar rate to sediment accumulation hence the majority of the skeletal material remained continuously embedded in the sediments and only a small proportion of the skeleton projected centimetres above the sediment surface the architectural palaeoecological sedimentological and diagenetic implications of different types of growth fabric genesis is discussed a review of the classification of reef fabrics suggests that there is currently no adequate system to describe fossil scleractinian growth fabrics the most commonly used classification of reefal fabrics is that of embry and klovan 1971 embry a f klovan j e 1971 a late devonian reef tract on northeastern banks island northwest territories bull can pet geol 33 730 781 there are a number of shortcomings in this scheme which may be grouped into three categories 1 the interpretative nature of the classification 2 problems in interpreting biological effect from form and 3 insufficient categories to adequately describe mesozoic and cenozoic growth fabrics moreover there appears to be a lack of a standardised nomenclature for growth fabrics which has hindered meaningful comparisons of scleractinian growth fabrics through time and space a descriptive system based on a modification and expansion of the embry and klovan system 1971 is proposed and a revised nomenclature for growth fabrics presented the system is designed to be flexible in its application it can be used simply to describe a growth fabric or through the use of genetic and non genetic modifiers to imply types of reef building processes and growth fabric heterogeneity although the concepts and terminology discussed in this paper relate to scleractinian growth fabric they are equally applicable to fabrics comprising other organisms

reef geometries erosion surfaces and high frequency sea level changes upper miocene reef complex mallorca spain the upper miocene reef complex of mallorca is a 20 km prograding unit which crops out in sea cliffs along the southern side of the island these vertical and exceptionally clean outcrops permit i identification of different facies lagoon reef front reef slope and open platform and their geometries and boundaries at different scales ranging from metre to kilometre and ii construction of a 6 km long high resolution cross section in the direction of reef progradation this cross section shows vertical shifts of the reefal facies and erosion surfaces linked to a general progradational pattern that defines the accretional units four hierarchical orders of magnitude 1 m to 4 m of accretional units are identified by consideration of the vertical facies shifts and by which erosion surfaces are truncated by other erosion surfaces all these orders show similar patterns horizontal beds of lagoonal facies in the upper part landward reefal and slope facies with sigmoidal bedding in the central part and open platform facies with subhorizontal bedding in the lower part basinwards the boundaries are erosion surfaces horizontal over the lagoon facies dipping basinwards over the reef front facies and connecting basinwards with their correlative conformities over the reef slope and open platform facies the four orders of accretional units are interpreted in terms of four 1 m to 4 m hierarchies of sea level cycles because i there is a close relation between the coral growth and the sea surface ii there are vertical shifts in the reefal facies and their relation to the erosion surfaces and iii there was very little tectonic subsidence in the study area during the late miocene additionally all these units can be described in terms of their position relative to the sea level cycle i the reefs prograde on the open platform sediments during low stands of sea level ii aggradation of the lagoon reef and open platform facies dominates during sea level rises and the lagoonal beds onlap landwards upon the previous erosion surface iii reefal progradation occurs during high stands of sea level and iv the 2 m sea level fall produces an off lapping reef and there is progradation with downward shifts of the reefal facies and erosion landward on the emerged older reefal units a erosion surfaces the 3 m and 4 m sea level falls produce only erosion b and c erosion surfaces although precise age data do not exist at present some speculations upon the frequency of these miocene relative sea level cycles can be made by comparisons with pleistocene cyclicity there is a good correlation between the miocene 2 m cycles and the 100 ka pleistocene cycles consequently the 1 m cycles can be assigned to a fourth order in relation to previously proposed global cycles and the 2 m to fifth order cycles all these accretional units could be defined as sequences according to the definition as commonly used in sequence stratigraphy however they represent higher than third order sea level cycles but are not parasequences the term subsequence therefore is suggested to define a part of a sequence bounded by erosion surfaces mostly subaerial and their correlative conformities basinwards a hierarchy of subsequences can be established

δ18o and δ13c of permian brachiopods a record of seawater evolution and continental glaciation abstract two hundred sixty four 18 o and 13 c values of permian articulate brachiopod shells were analyzed and 81 of these values were characterized as well preserved and biostratigraphically well defined these were then utilized for construction of baseline oxygen and carbon isotope curves for the permian interval in addition 21 13 c whole rock values are reported for the wordian and capitanian the early permian asselian to artinskian times are characterized by 2 5 decrease in oxygen isotope values from 0 7 to 3 3 v pdb this is attributed to a 4 7 c increase in temperature in the southern urals concomitant with the retreat of the permo carboniferous ice sheets and return of the 18 o depleted melt water into the oceans the late permian samples from iran jolfa at kuh e ali bashi and china meishan yield 18 o values and presumably temperatures similar to those that followed the termination of the large scale glaciation in the lower permian in between the upper kungurian to capitanian samples from the delaware basin guadalupe mountains are enriched in 18 o at 1 5 to 3 we have no definitive explanation for these data but tentatively suggest that the anomaly can potentially be a result of evaporative enrichment of seawater in 18 o due to intracratonic arid setting of the basin the 18 o enriched nature of the zechstein samples 1 2 to 2 5 on the other hand is in all probability a reflection of the high evaporation rates in the zechstein sea the permian interval is characterized by a relatively constant 13 c at about 4 the exceptions are again the brachiopods from the delaware basin guadalupe mountains which show 1 6 increase in the guadalupian to values of up to 5 9 in the wordian a tentative explanation as in the case of oxygen is based on the proposition that the semi enclosed delaware basin was likely stratified with sequestration of the 13 c depleted carbon to the deeper water layers and a complementary 13 c enrichment in the upper oxygenated layer the coeval open ocean water dic may have been similar to that of the remainder of the permian interval at 4 as indicated by whole rock carbonate samples from oman sicily and iran in the latest permian the trend mimics the well known 13 c drop at the permian triassic boundary

coral reefs in coarse terrigenous sedimentary environments upper tortonian granada basin southern spain abstract during the upper tortonian coral reefs developed on fan deltas and braid deltas along the active eastern edge of the granada basin the corals grew in environments characterized by deposition of coarse sands and conglomerates frequency of sedimentation together with sea level rises controlled reef development and determined the architecture and composition of the carbonate deposits in direct contrast to these reefs others flourished at the same time along stable coastal margins of the basin their structure was influenced mainly by periodic rises in sea level the mapping of all these reefs serves as an accurate guide to the upper tortonian geography of the granada basin

ludlow silurian stromatoporoid biostromes from gotland sweden facies depositional models and modern analogues stacked stromatoporoid dominated biostromes of the ludlow age hemse group silurian in eastern gotland sweden are 0 5 5 m thick and a few tens of metres to 1 km in lateral extent they form one of the world s richest palaeozoic stromatoporoid deposits this study compiles published and new data to provide an overall facies model for these biostromes which is assessed in relation to possible modern analogues some biostromes have predominantly in place fossils and are regarded as reefs but lack rigid frameworks because of abundant low profile non framebuilding stromatoporoids other biostromes consist of stromatoporoid rich rudstones interpreted here as storm deposits variation between these two end members occurs both between interlayered biostromes and also vertically and laterally within individual biostromes such variation produces problems of applying established reef classification terms and demonstrates the need for the development of terminology that recognizes taphonomic destruction of reef fabrics an approach to such terminology is found in all four categories of a recent biostrome classification scheme that are easily recognized in the hemse biostrome facies autobiostromes 60 in place autoparabiostromes a mixture of in place and overturned reef building organisms 20 60 in place parabiostromes builders are overturned and damaged 20 in place and allobiostromes transported and detrital reef material nothing in place these categories provide a broad taphofacies scheme for the hemse biostromes which are mostly autoparabiostrome to allobiostrome the biostromes developed on crinoidal grainstone sheets and expanded laterally across relatively flat substrates in a marine setting of low siliciclastic input planar erosion surfaces commonly terminate biostrome tops three broadly similar modern analogues are identified each of which has elements in common with the hemse biostromes but none of which is an exact equivalent a laterally expanded and coalesced back barrier patch reefs behind the belize barrier an area influenced by limited accommodation space b a hurricane influenced shelf interpreted for grand cayman where reef cores consist of rubble and lack substantial framework the wide distribution of rounded pebbles and cobbles of stromatoporoids in the hemse biostromes most probably resulted from hurricanes c coral carpets in 5 15 m water depth of the northern red sea where lateral expansion of low diversity frames dominated by porites coral has produced low profile biostromes up to 8 m thick and several km long such carpets accumulated large amounts of carbonate with little export as in the hemse biostromes although the latter did not build frameworks because of the nature of growth of the stromatoporoids the notable lack of algae in the hemse biostrome facies is also a feature of red sea coral carpets nevertheless coral carpets are ecologically different hemse biostromes lack evidence of a barrier reef system although this may not be exposed the facies assemblage is consistent with either a storm hurricane influenced mid to upper ramp or back barrier system less

dynamics and mass balance of taylor glacier antarctica 2 force balance and longitudinal coupling 1 taylor glacier antarctica exemplifies an ice sheet outlet that flows through a region of rugged topography and dry climate in contrast to other well studied outlets taylor glacier moves very slowly despite a thickness of order 1 km and driving stresses averaging 1 5 bars here we analyze new measurements of glacier geometry and surface velocity to elucidate flow dynamics of taylor glacier force balance and basal temperatures are calculated at six locations along the glacier s length using an algorithm developed for this study the effects of stress gradient coupling on longitudinal flow variations are also examined we ask whether kamb and echelmeyer s 1986 linearized theory adequately describes the observed response of flow to large amplitude variations in driving stress the force balance calculations indicate that no basal motion is needed to explain the observed flow of taylor glacier inferred basal temperatures are within a few degrees of the melting point in regions of kilometer thick ice and well below the melting point elsewhere deformation of subfreezing ice largely controls the flow of taylor glacier basal drags are mostly in the range 0 9 to 1 2 bars and lateral drags are in the range 0 2 to 0 5 bar stress gradient coupling strongly reduces the variability of velocities along the glacier the velocity variations can be described as the convolution of a forcing function with a spatial filter as kamb and echelmeyer suggested but the form of the forcing function differs from the theoretical relation derived for small amplitude perturbations the power on driving stress is one not three

why there was not a younger dryas like event during the penultimate deglaciation abstract the younger dryas cold event is a relatively unique feature of the last deglaciation when compared to previous deglaciations suggesting a unique trigger rather than the commonly held forcing mechanism of north american freshwater routing to the north atlantic here i compare the last t i and penultimate t ii deglaciations and provide new support for the argument that the lack of a younger dryas like event during t ii is due to the rapidity of northern hemisphere ice sheet retreat under greater boreal summer insolation forcing faster ice retreat suppressed atlantic meridional overturning circulation amoc until near the end of t ii while during t i amoc increased relatively early during t i the eastward routing of freshwater that caused the younger dryas happened after amoc resumption whereas during t ii this routing occurred prior to the resumption of amoc thus the increased flux of freshwater to the north atlantic during t ii had little effect on amoc explaining the lack of a younger dryas like climate oscillation during this deglaciation

biotic changes and their control on oligocene miocene reefs a case study from the apulia platform margin southern italy abstract the oligocene miocene represents for the cenozoic a period of extensive reef development and is characterized by a number of important changes influencing both carbonate producing biota and architecture of reefs and carbonate platforms the mediterranean region in particular was characterized during this time by a complex palaeogeographic and climatic history with stepwise transition towards cooler conditions biotic turnovers and the complete disappearance of zooxanthellate corals and reefs at the very end of the miocene a comparative study of two reef complexes that in different times chattian and messinian grew in the same physiographic and depositional setting i e the stable undeformed eastern margin of the apulia platform eastern coast of the salento peninsula southern italy highlights evolutionary ecological and climatic changes that differentiate oligocene and late miocene reef biota of the region in particular the study illustrates how different reef biotic assemblages can produce different reef types frameworks and growth fabrics along reef tracts and reef slopes the chattian reef is characterized by a homogeneous reef building biota being largely dominated by a high diversity and abundant coral fauna associated with a moderate presence of coralline algae and thus forming a single reef type in contrast the messinian reef shows a very low coral diversity but several other reef building components with abundant and varied secondary reef builders coralline algae halimeda encrusting foraminifera bryozoans serpulids and microbial associations the reef therefore is characterized by a heterogeneous reef building biota that forms different frameworks and growth fabrics the feedback to the environment of this different biotic composition is very evident in the two reefs and especially in the slope during the chattian a slope mainly consisting of gravity displaced debris resulted from the abundant production of reef rubble associated with a relatively poor framebuilding capacity conversely during the messinian a biologically stabilized slope resulted from proliferation of a variety of binding organisms that strongly colonized the substrate the climatic cooling which occurred during the miocene may be considered the main controlling factor of the diversity turnovers and changes that affected the coral fauna but other environmental factors such as changes in nutrient regimes and in hydrodynamic conditions of the sea associated with the emerging apennine chain may have played a role in determining differences in the reef biota and in the reef facies

how is the ocean filled 1 the ocean surface rapidly exchanges heat freshwater and gases with the atmosphere but once water sinks into the ocean interior the inherited properties of seawater are closely conserved previous water mass decompositions have described the oceanic interior as being filled by just a few different property combinations or water masses here we apply a new inversion technique to climatological tracer distributions to find the pathways by which the ocean is filled from over 10 000 surface regions based on the discretization of the ocean surface at 2 by 2 resolution the volume of water originating from each surface location is quantified in a global framework and can be summarized by the estimate that 15 of the surface area fills 85 of the ocean interior volume ranked from largest to smallest the volume contributions scaled by surface area follow a power law distribution with an exponent of 1 09 0 03 that appears indicative of the advective diffusive filling characteristics of the ocean circulation as demonstrated using a simple model this work quantifies the connection between the surface and interior ocean allowing insight into ocean composition atmosphere ocean interaction and the transient response of the ocean to a changing climate

vermetid reefs and their use as palaeobathymetric markers new insights from the late miocene of the mediterranean southern italy crete abstract vermetids are a poorly known family of reef building gastropods characterized by an extremely irregular growth of the shell vermetid reefs are known from the badenian middle miocene to present day and their main importance is related to their use as sea level indicators strictly associated to the intertidal or immediate subtidal zone during their evolution two different vermetid genera have been recognized as reef builders petaloconchus was the major component of vermetid reefs until the holocene when for still unknown reasons it was almost completely replaced by dendropoma in the mediterranean basin petaloconchus reefs have been frequently found in close association to late miocene coral bioconstructions new finding of petaloconchus reefs within the slope facies of the salento messinian reef complex southern italy together with new data from late tortonian early messinian reefs of crete greece provide further information on the palaeoecology of these peculiar bioconstructions stratigraphical and sedimentological contexts of salento and crete vermetid reefs have been described together with an account of their size shape and inner structure biotic vermetids serpulids bryozoans and coralline algae and abiotic components early marine cements and intra reef sediment have been identified by microfacies analysis and their percentage abundance has been reported these data allow the description of vermetid reefs from two different depositional settings along the shelf edge and for the first time within the coral reef slope shelf edge and slope petaloconchus reefs show the same inner structure and composition but they differ by their shape by the density of the framework and by the relative proportion of the associated reef building organisms serpulids bryozoans and coralline algae additional information on their palaeobathymetric setting have been acquired from the presence of other reef building biota porites corals and halimeda green algae which occur in close proximity to slope vermetid reefs together with observations on some anatomical feature of petaloconchus shells results clearly indicate for petaloconchus reefs a palaeobathymetric range spanning from the upper subtidal zone down to 30 50 m of depth the present study confirms vermetid reefs as important tools for the reconstructions of ancient sea level but great attention has to be paid to the identification of the main reef building vermetid actually while a great number of present day dendropoma reefs can be associated to the mean sea level late miocene vermetid reefs from salento and crete indicate for petaloconchus bioconstructions a wider palaeobathymetric range

evolution of ocean temperature and ice volume through the mid pleistocene climate transition earth s climate underwent a fundamental change between 1250 and 700 thousand years ago the mid pleistocene transition mpt when the dominant periodicity of climate cycles changed from 41 thousand to 100 thousand years in the absence of substantial change in orbital forcing over this time an increase occurred in the amplitude of change of deep ocean foraminiferal oxygen isotopic ratios traditionally interpreted as defining the main rhythm of ice ages although containing large effects of changes in deep ocean temperature we have separated the effects of decreasing temperature and increasing global ice volume on oxygen isotope ratios our results suggest that the mpt was initiated by an abrupt increase in antarctic ice volume 900 thousand years ago we see no evidence of a pattern of gradual cooling but near freezing temperatures occur at every glacial maximum

possible refugia for reefs in times of environmental stress this paper investigates the refuge potential of 1 upwelling areas 2 coral areas at medium depth and 3 offshore bank and island reefs in a scenario of increased global warming and thus increased sea surface temperature sst and increased solar uv radiation 1 observations on coral health and water temperature in the subtropical atlantic eleuthera and cat island bahamas and indian ocean sodwana bay south africa suggest a link between cool water delivered by upwelling and coral health after the 1998 bleaching event caused by strong sst anomalies coral health and recovery from the previous year s bleaching was significantly better on the narrow southern cat island shelf 70 of corals healthy where the presence of cold water was observed which was attributed to small scale upwelling than on the wide northern eleuthera shelf 44 of corals healthy where downwelling of hot bank waters was believed to have damaged corals in south africa regular short term upwelling events in five summers reduced sst to well below bleaching level 2 in the northern red sea safaga bay and in south africa sodwana bay wide areas with either coral frameworks or non framework communities exist calculations show that if the top 10 m 20 m of the ocean became inhospitable to corals still 50 4 17 5 of the coral area would remain intact in the red sea and 99 40 in south africa 3 offshore bank and island reefs investigated in the turks caicos and mouchoir banks and grand and little cayman showed high rates of mortality and coral diseases the most remote sites mouchoir bank were not the healthiest refuge areas appear to exist in 1 and 2 but in 3 only if vigorous water circulation is encountered

two phase change in co2 antarctic temperature and global climate during termination ii the end of the last glacial maximum termination i roughly 20 thousand years ago ka was marked by cooling in the northern hemisphere a weakening of the asian monsoon a rise in atmospheric co2 concentrations and warming over antarctica the sequence of events associated with the previous glacial interglacial transition termination ii roughly 136 ka is less well constrained here we present high resolution records of atmospheric co2 concentrations and isotopic composition of n2 an atmospheric temperature proxy from air bubbles in the epica dome c ice core that span termination ii we find that atmospheric co2 concentrations and antarctic temperature started increasing in phase around 136 ka but in a second phase of termination ii from 130 5 to 129 ka the rise in atmospheric co2 concentrations lagged that of antarctic temperature unequivocally we suggest that during this second phase the intensification of the low latitude hydrological cycle resulted in the development of a co2 sink which counteracted the co2 outgassing from the southern hemisphere oceans over this period

pyroclastic rocks another manifestation of ultramafic volcanism on gorgona island colombia tertiary ultramafic volcanism on gorgona island colombia is manifested not only by komatiite flows but also by a more voluminous sequence of tuff breccias which is cut by comagmatic picrite dikes the ultramafic pyroclastic rocks are chaotic to stratified mixtures of angular to subrounded glassy picritic blocks and a fine grained volcaniclastic matrix that consists primarily of plastically deformed glassy globules the entire deposit is interpreted to have formed by an explosive submarine eruption of phenocryst laden picritic magma mgo contents of tuff breccias and picrite dikes range from 21 to 27 wt relative to nearby komatiite flows these rocks are mgo rich and feo tio2 and ni poor hree concentrations are very low seven times chondrite and similar to those of the komatiites whereas the lree are extremely fractionated ce sm n 0 2 indicating derivation from a more highly depleted mantle source region nd isotopic data suggest a cogenetic relationship between the picritic magma that formed the tuff breccia and associated dikes and that which produced the komatiite flows nevertheless pb isotopic data as well as whole rock geochemistry preclude such a connection either due to olivine fractionation accumulation or to different degrees of partial melting these ultramafic rock types crystallized from magmas which most likely were extracted from distinct mantle source regions

structure and development of detrital reef deposits in turbid nearshore environments inhaca island mozambique coral communities are intermittently developed along the seaward margins of wide up to 500 m intertidal flats that fringe the western margins of inhaca island southern mozambique the coral communities occur in an environment that can be considered as marginal for coral growth in the sense that they are subject to high turbidity levels which results in rapid light attenuation and to the effects of periodic smothering and burial associated with a mobile siliciclastic dominated sediment substrate these constraints limit coral community development both spatially and bathymetrically in addition historical evidence suggests that the main sites of coral growth shift over decadal timescales due to periodic sediment remobilisation such rapid rates of turnover restrict the development of rigid framework deposits and in contrast the main depositional product of coral growth is an abundance of branched mainly acropora sp coral rubble rubble production is aided both by intense internal bioerosion sponge bivalve and worm traces and by periodic storm damage much of this rubble accumulates along the channel margins and provides a substrate for subsequent coral recruitment the deposits can be distinguished from those associated with clear water reef environments by 1 the lack of a rigid reef framework either comprising of in situ coral or encrusted coral rubble 2 the distinct lack of rubble encrustation syn depositional cementation and 3 the predominance of a siliciclastic rich sediment matrix the deposits indicate however a long term history of coral community occurrence in sites dominated by siliciclastic sedimentation cores recovered from a transect across the tidal flats identify a coral rubble floatstone facies extensively developed along the western margins of the island it comprises mainly branched coral rubble often heavily bioeroded but sparsely encrusted along with spheroidal rhodoliths and molluscan fragments set within a poorly sorted mixed siliciclastic carbonate sediment matrix 14c dating indicates that most of the rubble deposits date from the period 6500 4700 years bp which corresponds to a period of regional sea level highstand a detailed growth chronology cannot be established due to the lack of in situ coral but rapid rubble deposition and reef flat progradation around 350 m can be inferred for this period equivalent to an average progradation rate of around 0 2 m year 1 over the subsequent 4700 years progradation of only around 25 m has occurred this may be attributed to reworking and erosion of the seaward margin of the deposits during periods of fluctuating sea level between 4700 and 900 years bp or to a lack of seaward accommodation space

on the glaciological meteorological and climatological significance of antarctic blue ice areas this paper presents the current state of our knowledge about antarctic blue ice areas scattered widely over the antarctic continent yet covering only approximately 1 of its surface area blue ice areas have some peculiar characteristics that make them of particular interest for planetary geologists glaciologists meteorologists and climatologists for instance blue ice areas are subject to net ablation mainly by sublimation since any accumulation is easily swept off their smooth surfaces by winds moreover they are significantly warmer than their surroundings and the wind over them is generally more gusty an important feature of blue ice is its relatively low albedo 0 56 compared with that of snow 0 80 blue ice is probably considerably smoother than snow in the aerodynamic sense with roughness lengths as low as 3 10 6 m which indicates that blue ice is probably the only permanent natural surface over which the air flow is mainly in the aerodynamic smooth regime further since it is likely that very old ice is exposed at the surface of some blue ice areas this ice would be of great interest for paleoclimatic studies it has also been suggested that blue ice areas are sensitive to climate change this would make them useful as antarctic climate indicators because they can easily be monitored by satellite finally this paper addresses several gaps in our knowledge about blue ice areas and gives suggestions for future blue ice area research

tropical tales of polar ice evidence of last interglacial polar ice sheet retreat recorded by fossil reefs of the granitic seychelles islands abstract in the search for a record of eustatic sea level change on glacial interglacial timescales the seychelles ranks as one of the best places on the planet to study owing to its location with respect to the former margins of northern hemisphere ice sheets that wax and wane on orbital cycles the local or relative sea level history is predicted to lie within a few meters of the globally averaged eustatic signal during the last interglacial period we have surveyed and dated last interglacial fossil corals to ascertain peak sea level and hence infer maximum retreat of polar ice sheets during this time interval we observe a pattern of gradually rising sea level in the seychelles between 129 and 125 thousand years ago ka with peak eustatic sea level attained after 125 ka at 7 6 1 7 m higher than present after accounting for thermal expansion and loss of mountain glaciers this sea level budget would require 5 8 m of polar ice sheet contribution relative to today s volume of which only 2 m came from the greenland ice sheet this result clearly identifies the antarctic ice sheet as a significant source of melt water most likely derived from one of the unstable marine based sectors in the west and or east antarctic ice sheet furthermore the establishment of a 5 9 1 7 m eustatic sea level position by 128 6 0 8 ka would require that partial ais collapse was coincident with the onset of the sea level highstand

a method to measure kr n2 ratios in air bubbles trapped in ice cores and its application in reconstructing past mean ocean temperature 1 we describe a new method for precise measurement of kr n2 ratios in air bubbles trapped in ice cores and the first reconstruction of atmospheric kr n2 during the last glacial maximum lgm 20 000 years ago after gravitational correction the kr n2 record in ice cores should represent the atmospheric ratio which in turn should reflect past ocean temperature change due to the dependence of gas solubility on temperature the increase in krypton inventory in the glacial ocean due to higher gas solubility in colder water causes a decrease in the atmospheric inventory of krypton assuming kr and n2 inventories in the ocean atmosphere system are conserved we use a mass balance model to estimate a mean ocean temperature change between the lgm and today we measured kr n2 in air bubbles in greenland gisp2 ice from the late holocene and lgm using the present atmosphere as a standard the late holocene kr n2 means from two sets of measurements are not different from zero 0 07 0 30 and 0 14 0 93 as expected from the relatively constant climate of the last millennium the mean kr n2 in air bubbles from the lgm is 1 34 0 37 using the mass balance model we estimate that the mean temperature change between the lgm ocean and today s ocean was 2 7 0 6 c although this error is large compared to the observed change this finding is consistent with most previous estimates of lgm deep ocean temperature based on foraminiferal 18o and sediment pore water 18o and chlorinity

reef building and carbonate production modes in the west central tethys during the cenozoic abstract changing components rock textures lithofacies platform types and architecture throughout time are unique characteristics of carbonate rocks characterizing these attributes has been approached by 1 building reference models for specific phanerozoic intervals 2 recognizing the climatic impact in modulating carbonate production and 3 analyzing the influence of changing bio geochemical conditions the reference model approach is mostly based on biological evolution the climatic impact approach emphasizes temperature and the bio geochemical approach considers the changes in mg ca ratios and ca concentrations in the oceans to date however an analysis integrating all of these factors is still missing the analysis presented here includes all these factors but also co 2 which is fundamental for both photosynthesis and caco 3 precipitation here we analyze the waxing and waning of cenozoic reef limestones from the central tethys region through several steps 1 on the basis of rock volume rock textures associated sediments and light dependent skeletal components as records of light penetration and wave energy depth 2 on global environmental conditions 13 c 18 o p co 2 temperature and 3 on the basis of functionality nutritional requirements and available resources through the cenozoic water motion whether induced by surface or internal waves or by currents increased as the thermal gradients strengthened both with depth and with latitude active water motion is essential for plankton catchers such as corals but less so for many larger benthic foraminifers lbf pycnoclines in the meso oligophotic zone would then favor the benthic plankton catchers such as corals but would be detrimental for many lbf warm temperatures favored lbf the eocene lbf families predominated during lowering of atmospheric p co 2 by using respiratory co 2 to enhance the symbiont production of photosynthates under oligotrophic conditions and limited turbulence whereas the miocene families had to adapt to a progressive increase in turbulence the eurythermal coralline red algae however became preponderant producers in the mesophotic zone during times when the 13 c was relatively high this explains two apparent paradoxes 1 corals thrive best when the earth s high latitudes cool and 2 the dominance of corals and lbf is inversely correlated despite they both require tropical conditions and have similar trophic strategies mixotrophy

upper jurassic microsolenid biostromes of northern and central europe facies and depositional environment abstract microsolenid biostromes are a common and important reef type in many upper jurassic reefal sections comparative study of these biostromes in western europe allows the characterisation of this distinct biostrome type in terms of its taxonomic composition palaeoecology and sedimentary regime the biostromes are characterised by a coral community of relatively low generic diversity being dominated by the microsolenidae family of corals the coral skeletal biovolume is generally high and is overwhelmingly dominated by platy ecomorphotypes sedimentologically these biostromes developed in low energy marl and limestone regimes which were subject to low sedimentation rates and varying degrees of siliciclastic influx in contrast to the coral fauna the associated fauna shows a high generic diversity in particular a rich assemblage of echinoids and bivalves in addition the coral plates provide an ideal habitat for a well developed and strongly polarised encrusting and boring fauna top surfaces show limited post mortem encrustation by serpulids and cementing bivalves and are also bored by lithophagan bivalves the undersides of the plates show a highly developed and diverse cryptic fauna of serpulids thecidean brachiopods bryozoans calcareous sponges and sclerosponges it is concluded that the main control on the development of these biostromes was low light intensities though low energy level and low background sedimentation rates were also important it is suggested that relatively high nutrient levels may have also played a significant role the conditions for microsolenid biostrome development prevail in relatively deep water environments and hence these are the first coral dominated reefal structures to have developed in deeper water shallowing upward sequences the corals in these biostromes have adapted to these conditions by developing a strongly platy growth form but also reducing their growth rates substantially the microsolenids are particularly adapted to these environments in two ways 1 they secreted an extremely porous calcium carbonate skeleton which in environments where calcification rates are slow such as deep water environments is a distinct advantage 2 in response to the limited potential of phototrophy in these environments the microsolenids have developed a pennular septal structure which is suggested to be a means of improving heterotrophic feeding trophic analysis of the reef fauna reveals that the nutrient limitation model developed for present day coral reefs cannot be applied to these biostromes it is demonstrated that the microsolena and the present day agariciid leptoseris show a number of significant morphological and ecological similarities

off reef transport of coral fragments at lizard island australia abstract the generation and movement of coral rubble is important to the sedimentary budget of a reef in sediment facies development and in the promotion of reef growth this study examined the rate of down slope transport of live and dead coral fragments from shallow reef fronts at lizard island on the great barrier reef australia ten large 1 m2 collecting trays were deployed and cleared annually for 4 years at each of two sites at the base 8 12 m depth of the steeply sloping fringing reef the rate of export of coral fragments down the reef slope was very high an average of 132 fragments weighing 1 87 kg was recorded each year per meter of reef front a mean of 2 25 of the fragments representing 43 species was alive in the trays at each annual census yielding an average rate of colonization onto the reef slope of 2 7 live fragments per meter of reef front per year reworking of hard calcareous substrates towards the slope promotes reef growth by two mechanisms 1 passive dispersal of live coral fragments to peripheral soft sediment habitats that are unsuitable for larval settlement and 2 subsequent colonization of rubble by coral larvae there were no major storms during the course of the study indicating that significant down slope transport of fragments can occur even in the absence of cyclones

inhibition of reef framework by frequent disturbance examples from the arabian gulf south africa and the cayman islands abstract the environmental processes that prevent reef framework development in areas with a diverse and dense cover of coral were investigated in the southern arabian gulf dubai uae the southwestern indian ocean south africa and the central caribbean cayman islands bwi in dubai temperature anomalies predicted to recur every 10 15 yr cause repeated mass mortalities of acropora spp the dominant potential framebuilding species subsequent bioerosion of the dead coral skeletons renders them brittle and susceptible to fragmentation during winter storms as a consequence regrowth of the next generation of framebuilders which takes about 10 yr has to initiate on the original bedrock surface this cycle of mass mortality framework break down and regrowth inhibits in situ framework accumulation in south africa the formation of coral frameworks is prevented by annually recurring high wave energy events which stunt coral to such small sizes that no framework is built the situation is further aggravated by the fact that branching coral fragments which could serve as asexual propagules are washed off the reefs and lost in the cayman islands no coral framestones of in situ skeletons are formed in areas shallower than about 5 m in these areas coral frameworks formed by acropora palmata are removed by hurricanes broken up and deposited in the form of a rubble accumulation further inland on the island shelf thus although a coral deposit remains it is not an in situ grown framework however since the build ups in the upper 5 m are mostly made up by coral fragments such structures would likely be identified as reefs if encountered in a fossil outcrop situation these three models can help to explain the paleoecology of allochthonous peri reefal or non reefal coral deposits i e coral rudstones floatstones bindstones they also demonstrate that at least in recent coral systems species richness and high coral coverage alone need not necessarily translate into high in situ framebuilding potential

antarctic ice sheet loss driven by basal melting of ice shelves accurate prediction of global sea level rise requires that we understand the cause of recent widespread and intensifying glacier acceleration along antarctic ice sheet coastal margins atmospheric and oceanic forcing have the potential to reduce the thickness and extent of floating ice shelves potentially limiting their ability to buttress the flow of grounded tributary glaciers indeed recent ice shelf collapse led to retreat and acceleration of several glaciers on the antarctic peninsula but the extent and magnitude of ice shelf thickness change the underlying causes of such change and its link to glacier flow rate are so poorly understood that its future impact on the ice sheets cannot yet be predicted here we use satellite laser altimetry and modelling of the surface firn layer to reveal the circum antarctic pattern of ice shelf thinning through increased basal melt we deduce that this increased melt is the primary control of antarctic ice sheet loss through a reduction in buttressing of the adjacent ice sheet leading to accelerated glacier flow the highest thinning rates occur where warm water at depth can access thick ice shelves via submarine troughs crossing the continental shelf wind forcing could explain the dominant patterns of both basal melting and the surface melting and collapse of antarctic ice shelves through ocean upwelling in the amundsen and bellingshausen seas and atmospheric warming on the antarctic peninsula this implies that climate forcing through changing winds influences antarctic ice sheet mass balance and hence global sea level on annual to decadal timescales

fractionation of gases in polar ice during bubble close off new constraints from firn air ne kr and xe observations gas ratios in air withdrawn from polar firn snowpack show systematic enrichments of ne n2 o 2 n2 and ar n2 in the firn ice transition region where bubbles are closing off air from the bubbles in polar ice is correspondingly depleted in these ratios after accounting for gravitational effects gas in the bubbles becomes fractionated during the process of bubble close off and fractionation may continue as ice cores are stored prior to analysis we present results from firn air studies at south pole and siple dome antarctica which add ne kr and xe measurements to the suite of observations ne o2 and ar appear to be preferentially excluded from the shrinking and occluding bubbles and these gases therefore accumulate in the residual firn air creating a progressive enrichment with time and depth in firn air early sealing of gases by thin horizontal impermeable layers into a nondiffusive zone or lock in zone greatly enhances this enrichment a simple model of the bubble close off fractionation and lock in zone enrichment fits the data adequately the model presumes that fractionation is caused by selective permeation of gas through the ice lattice from slightly overpressured bubbles the effect appears to be size dependent because ne o2 and ar have smaller effective molecular diameters than n2 and fractionation increases strongly with decreasing size ne is fractionated 34 2 times more than o2 in south pole firn air and reaches an enrichment of 90 in the deepest sample the large atoms kr and xe do not appear to be fractionated by this process despite the large size difference between the two gases suggesting a threshold atomic diameter of 3 6a above which the probability becomes very small that the gas will escape from the bubble these findings have implications for ice core and firn air studies that use gas ratios to infer paleotemperature chronology and past atmospheric composition

oyster shells as recorders of short term oscillations of salinity and temperature during deposition of coral bioherms and reefs in the miocene lorca basin se spain abstract we use 18 o and 13 c of oyster shells inferred seawater 18 o w and temperature tolerance ranges of modern zooxanthellate coral communities to constrain and model paleo salinities of marginal marine waters of the miocene lorca basin spain salinities ranged from 22 to 32 psu during growth of coral bioherms and carpets of the soriana and parrilla formations and from 35 to 39 psu during deposition of the hondo formation reef complex the periods with lower modeled salinities correspond with deltaic and alluvial fan sedimentation in the area the modeling is supported by 87 sr 86 sr data and provides new insights into the evolution of the local depositional settings departures of sr isotope values from the global oceanic curve occur within the intervals with the lowest modeled salinities and the non oceanic 87 sr 86 sr preserved in individual oyster shells was probably sourced from uplifted aquitanian burdigalian limestones 87 sr 86 sr values that plot along the global ocean sr isotope curve for the late miocene indicate a tortonian age for the upper part of the soriana formation and the parrilla formation and a messinian age for the hondo formation more generally we demonstrate how the chemical analyses of oyster shells provide additional information regarding short term oscillations of salinity and temperature of seawater beyond what can be obtained by traditional paleoecological methods

carbonates calibrated against oceanographic parameters along a latitudinal transect in the gulf of california mexico trophic resources are an important control governing carbonate production though this importance has long been recognized no calibration exists to quantitatively compare biogenic assemblages within trophic resource fields this study presents a field calibration of carbonate producers in a range of settings against high resolution in situ measurements of nutrients temperature and salinity with its latitudinal extent from 30 to 23 n the gulf of california mexico spans the warm temperate realm and encompasses nutrient regimes from oligo mesotrophic in the south to eutrophic in the north accordingly from south to north carbonates are characterized by i coral dominated shallow carbonate factories 5 20 m water depth with average sea surface temperatures of 25 c min 18 c max 31 c average salinities of 35ae06 and average chlorophyll a levels which are a proxy for nutrients of 0ae25 mg chl a m 3 max 0ae48 min 0ae1 ii red algal dominated subtidal to inner shelf carbonate formation 10 25 m in the central gulf of california exhibiting average temperatures of 23 c min 18 c max 30 c average salinities of 35ae25 and average chl a levels of 0ae71 chl a m 3 max 5ae62 min 0 iii molluskan bryozoan rich inner to outer shelf factories in the northern gulf of california 20 50 m with average sea surface temperatures of only 20 c min 13 c max 29 c average salinities of 35ae01 and average contents of 2ae2 mg chl a m 3 max 8ae38 min 0 by calibrating sedimentological data with in situ measured oceanographic information in different environments the response of carbonate producers to environmental parameters was established and extrapolated to carbonates on a global scale the results demonstrate the importance of recognizing and quantifying trophic resources as a dominant control determining the biogenic composition and facies character of both modern and fossil carbonates

a high resolution absolute dated late pleistocene monsoon record from hulu cave china oxygen isotope records of five stalagmites from hulu cave near nanjing bear a remarkable resemblance to oxygen isotope records from greenland ice cores suggesting that east asian monsoon intensity changed in concert with greenland temperature between 11 000 and 75 000 years before the present yr b p between 11 000 and 30 000 yr b p the timing of changes in the monsoon as established with 230th dates generally agrees with the timing of temperature changes from the greenland ice sheet project two gisp2 core which supports gisp2 s chronology in this interval our record links north atlantic climate with the meridional transport of heat and moisture from the warmest part of the ocean where the summer east asian monsoon originates

a high resolution absolute dated holocene and deglacial asian monsoon record from dongge cave china abstract we present a continuous record of the asian monsoon over the last 16 ka from 18o measurements of stalagmite calcite over 900 oxygen isotopic measurements providing information on shifts in monsoon precipitation are combined with a chronology from 45 precise 230th dates 18o and therefore asian monsoon intensity generally follows changes in insolation although changes in 18o are generally accommodated in abrupt shifts in contrast to smoothly varying insolation indicating that threshold effects may be important 18o decreased dramatically 3 at the start of the holocene 11 5 ka and remained low for 6 ka four positive 18o events centered at 11225 97 yr bp 1 05 10880 117 yr bp 1 15 9165 75 yr bp 1 4 and a double event centered at 8260 64 yr bp 1 1 and 8080 74 yr bp 1 0 punctuated this period of high monsoon intensity all four events correlate within error with climate changes in greenland ice cores thus the relationship between the asian monsoon and the north atlantic observed during the glacial period appears to continue into the early holocene in addition three of the four events correlate within error with outburst events from lake agassiz the decline of monsoon intensity in the mid late holocene is characterized by an abrupt positive shift in 18o which occurs at 3550 59 yr bp 1 1 in 100 yr in addition the holocene is punctuated by numerous centennial and multi decadal scale events amplitudes 0 5 to 1 up to half the amplitude of the glacial interstadial events seen in the last glacial period thus holocene centennial and multi decadal scale monsoon variability is significant although not as large as glacial millennial scale variability the monsoon shows a strong connection with northern south american hydrological changes related by changes in itcz position spectral analysis of the 18o record shows significant peaks at solar periodicities of 208 yr and 86 yr suggesting variation is influenced by solar forcing however there are numerous other significant peaks including peaks at el nino frequencies observed for high resolution portions of the record between 8110 and 8250 yr which suggest that changes in oceanic and atmospheric circulation patterns in addition to those forced by solar changes are important in controlling holocene monsoon climate in addition for this high resolution portion we observe a distinctive biennial oscillation of the asian monsoon which has been associated with the tropospheric biennial oscillation tbo

temporal and spatial structure of multi millennial temperature changes at high latitudes during the last interglacial the last interglacial lig 129e116 thousand of years bp ka represents a test bed for climate model feedbacks in warmer than present high latitude regions however mainly because aligning different palaeoclimatic archives and from different parts of the world is not trivial a spatio temporal picture of lig temperature changes is difficult to obtain here we have selected 47 polar ice core and sub polar marine sediment records and developed a strategy to align them onto the recent aicc2012 ice core chronology we provide the first compilation of high latitude temperature changes across the lig associated with a coherent temporal framework built between ice core and marine sediment records our new data synthesis highlights non synchronous maximum temperature changes between the two hemispheres with the southern ocean and antarctica records showing an early warming compared to north atlantic records we also observe warmer than present day conditions that occur for a longer time period in southern high latitudes than in northern high latitudes finally the amplitude of temperature changes at high northern latitudes is larger compared to high southern latitude temperature changes recorded at the onset and the demise of the lig we have also compiled four data based time slices with temperature anomalies compared to present day conditions at 115 ka 120 ka 125 ka and 130 ka and quantitatively estimated temperature uncertainties that include relative dating errors this provides an improved benchmark for performing more robust model data comparison the surface temperature simulated by two general circulation models ccsm3 and hadcm3 for 130 ka and 125 ka is compared to the corresponding time slice data synthesis this comparison shows that the models predict warmer than present conditions earlier than documented in the north atlantic while neither model is able to produce the reconstructed early southern ocean and antarctic warming our results highlight the importance of producing a sequence of time slices rather than one single time slice averaging the lig climate conditions

palaeoecology of well preserved coral communities in a siliciclastic environment from the late pleistocene mis 7 kish island persian gulf iran the development of low relief reef frameworks biostromes in increasingly restricted environments major changes in community structure and depositional relief of high latitude coral communities in the southern persian gulf between marine isotope stage mis 7 and the present day suggest that the area has become increasingly restricted corals and bivalves from outcrops on kish island iran were identified in order to interpret the late pleistocene palaeoenvironmental setting u th disequilibrium dating was used to constrain the ages of the stratigraphic units during mis 7 two coral bearing sequences were deposited on what is now kish island the lower sequence is dated as mis 7 5 and changes laterally from an assemblage dominated by cyphastrea sp and platygyra daedalea in the west to one characterized by branching montipora in the east by contrast the upper sequence dated as mis 7 1 transitions from an assemblage dominated by platy montipora in the west to a diverse assemblage of platygyra and other faviids in the east the assemblages of both sequences are within a marl matrix and bounded by thin lithified mollusc rich layers corals and bivalves indicate that the sequences were deposited on gentle slopes in sheltered environments less than 20 m deep the mis 7 deposits may be classified as coral carpets or biostromes that developed a low relief framework during mis 5 coral communities were no longer framework building and are now limited to an acropora rich layer of coral rubble that covers large parts of the island and two small incipient reefs with sparse faviids similarities between the mis 5 and modern nearshore coral communities suggest that the environmental conditions during mis 5 were comparable to those of today the late pleistocene coral carpets and non framework coral communities of the southern persian gulf may serve as models for coral biostromes in the fossil record which formed under restricted environmental conditions such as elevated terrigenous input high turbidity and strong seasonal changes in temperature and or salinity