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Direct studies of recent epeiric seawater chemistry and their geological significance are relatively few compared to the far more abundant studies from ancient epeiric marine carbonates. Acknowledging the limitations of analogue studies in the modern glaciated world, we propose that the recent Abu Dhabi offshore and lagoonal areas share important attributes with the shallow-marine coastal zones of a subtropical epeiric carbonate sea. The study area in Abu Dhabi is dwarfed by the vast epeiric seas of the geological past, but its seawater properties and related geochemistry have relevance for paleoenvironmental interpretations for similar ancient systems. This study documents the geochemical properties of seawater along the Abu Dhabi coast, and discusses their trends within a spatial context. Results show a positive correlation between salinity, temperature, elemental concentrations, and oxygen isotopic composition of seawater, indicating a significant influence of evaporation on seawater chemistry. A distal-to-proximal negative correlation between seawater Mg/Ca and Sr/Ca ratios may be related to a landward increase in abundance of high-Mg calcite foraminifera. After normalization to chloride, seawater elemental (Ca2+, Mg2+, Sr2+) concentrations and alkalinity show decreasing trends in a landward direction, consistent with seawater aging from the open marine to restricted lagoonal settings. Lower ΔAlk (alkalinity change) : ΔCa2+ (Ca2+ change) ratios in seawater compared with the theoretical value, and more negative δ13CDIC values relative to typical (sub)tropical oceans in the study area indicate an influence of factors apart from CaCO3 precipitation on properties of aged seawater. An input of alkalinity and 12C-enriched carbon by organic carbon decomposition (via sulfate reduction) during early diagenesis is proposed to account for these deviations from typical values. The input of alkalinity and 12C-enriched carbon by organic carbon decomposition may be further related to reduced seawater pCO2 and early-marine cementation. Findings discussed here suggest that organic carbon decomposition during early-marine diagenesis may influence the geochemical properties of the coastal areas of shallow epeiric seas, and thus assumedly produce significant differences in proxy data compared with those from carbonates deposited in open oceans.

During glacial terminations, massive iceberg discharges and meltwater pulses in the North Atlantic triggered a shutdown of the Atlantic Meridional Overturning Circulation (AMOC). Speleothem calcium carbonate oxygen isotope records (δ18OCc) indicate that the collapse of the AMOC caused dramatic changes in the distribution and variability of the East Asian and Indian monsoon rainfall. However, the mechanisms linking changes in the intensity of the AMOC and Asian monsoon δ18OCc are not fully understood. Part of the challenge arises from the fact that speleothem δ18OCc depends on not only the δ18O of precipitation but also temperature and kinetic isotope effects. Here we quantitatively deconvolve these parameters affecting δ18OCc by applying three geochemical techniques in speleothems covering the penultimate glacial termination. Our data suggest that the weakening of the AMOC during meltwater pulse 2A caused substantial cooling in East Asia and a shortening of the summer monsoon season, whereas the collapse of the AMOC during meltwater pulse 2B (133,000 years ago) also caused a dramatic decrease in the intensity of the Indian summer monsoon. These results reveal that the different modes of the AMOC produced distinct impacts on the monsoon system., Nature Geoscience, 14 (12), ISSN:1752-0908, ISSN:1752-0894

Historical coral skeleton (CS) δ18 O and δ15 N records were produced from samples recovered from sedimentary deposits, held in natural history museum collections, and cored into modern coral heads. These records were used to assess the influence of global warming and regional eutrophication, respectively, on the decline of coastal coral communities following the development of the Pearl River Delta (PRD) megacity, China. We find that, until 2007, ocean warming was not a major threat to coral communities in the Pearl River estuary; instead, nitrogen (N) inputs dominated impacts. The high but stable CS-δ15 N values (9‰-12‰ vs. air) observed from the mid-Holocene until 1980 indicate that soil and stream denitrification reduced and modulated the hydrologic inputs of N, blunting the rise in coastal N sources during the early phase of the Pearl River estuary urbanization. However, an unprecedented CS-δ15 N peak was observed from 1987 to 1993 (>13‰ vs. air), concomitant to an increase of NH4+ concentration, consistent with the rapid Pearl River estuary urbanization as the main cause for this eutrophication event. We suggest that widespread discharge of domestic sewage entered directly into the estuary, preventing removal by natural denitrification hotspots. We argue that this event caused the dramatic decline of the Pearl River estuary coral communities reported from 1980 to 2000. Subsequently, the coral record shows that the implementation of improved wastewater management policies succeeded in bringing down both CS-δ15 N and NH4+ concentrations in the early 2000s. This study points to the potential importance of eutrophication over ocean warming in coral decline along urbanized coastlines and in particular in the vicinity of megacities.

Human activities within the context of a drying trend triggered the megafaunal extinctions in Madagascar and Mascarene Islands., Madagascar and the Mascarene Islands of Mauritius and Rodrigues underwent catastrophic ecological and landscape transformations, which virtually eliminated their entire endemic vertebrate megafauna during the past millennium. These ecosystem changes have been alternately attributed to either human activities, climate change, or both, but parsing their relative importance, particularly in the case of Madagascar, has proven difficult. Here, we present a multimillennial (approximately the past 8000 years) reconstruction of the southwest Indian Ocean hydroclimate variability using speleothems from the island of Rodrigues, located ∼1600 km east of Madagascar. The record shows a recurring pattern of hydroclimate variability characterized by submillennial-scale drying trends, which were punctuated by decadal-to-multidecadal megadroughts, including during the late Holocene. Our data imply that the megafauna of the Mascarenes and Madagascar were resilient, enduring repeated past episodes of severe climate stress, but collapsed when a major increase in human activity occurred in the context of a prominent drying trend.

In the context of human evolution and dispersal in Africa, it is important to understand past climate conditions and changes as possible drivers of these processes. One of the most recent climatic events was the end of the African Humid Period (AHP) at around 5 ka BP. This was marked by a decrease in precipitation following a long wet-phase in northern and eastern Africa, which caused many lakes to decrease in size or even desiccate. Although the termination of the AHP is well known, the timing and rate of the transition from wet to dry conditions is still heavily debated. To investigate the termination of the AHP at a high temporal resolution (subdecadal and subannual), fossil stromatolites and Etheria elliptica shells from paleo-shorelines in the Chew Bahir Basin, southern Ethiopia, were collected. Today, Lake Chew Bahir is a deltaic swamp, however in past pluvials a large lake was present that likely overflowed and connected to other basins similar to other amplifier lakes in the East African Rift System. Radiocarbon dating, oxygen and carbon stable isotope analyses, trace element analyses and petrographic mapping of stromatolite laminae structure were conducted. A strong correlation between δ18O and δ13C shows that paleo-lake Chew Bahir likely experienced highly evaporative conditions and indicate an endorheic state of the basin in times of stromatolite growth at 7.1, 5.8, 4.7 and 4.6 ka BP. Furthermore, our findings suggest highly fluctuating environmental conditions during these times and demonstrate that the transition to drier conditions was not a strictly linear trend. In summary, the stromatolites and Etheria elliptica shells are an excellent environmental archive due to their high temporal resolution, precise dating (± 30 yrs) and an indication of the paleo-lake water depth. These types of records provide insights to past changes in freshwater availability, the variability of which would have had large consequences for humans living in the region.

Most paleoceanographic studies using planktic foraminifera focus on annual means, but seasonal signals buried by the analyses of lumped specimens could be very valuable. Surface ocean feedbacks on climate change may be more significant in the seasonal realm than annual mean in the northern South China Sea, a region being strongly affected by Asian monsoons and tropical cyclones. Here we use oxygen isotope measurements on individual specimens of surface and subsurface planktic foraminiferal species to reconstruct surface seasonality and seasonal upper ocean stratification in this region. Many studies have shown that the thermocline was deeper in the tropical Pacific during the Pliocene than the Pleistocene, but the mechanism remains unclear. Several processes could lead to changes in the upper ocean stratification, such as changes in sea surface temperature and upper ocean mixing by tropical cyclones. Our results show that the upper ocean stratification was weaker during the Late Pliocene than the Early Pleistocene, with the change more significant in summer than winter, while no systematic offset is observed in the surface seasonality. The observations suggest that enhanced mixing by tropical cyclones might be the major cause of the deeper thermocline during the Pliocene.

The Caspian Sea is an evolutionary island whose rich and endemic fauna have evolved in partial isolation over the past two million years. Baseline studies of pre-20th Century communities are needed in order to assess the severity of the current Caspian biodiversity crisis, which mostly involves invasive species. An inventory of late Holocene shelly assemblages (c. 2000–2500 cal yr BP) from outcrops in and around Great Turali Lake (Dagestan, Russia) shows a diverse nearshore community consisting of 24 endemic Caspian species, two invasive species and two Caspian native species that lived in a shallow embayment with mesohaline salinities of circa 5–13 psu (parts per thousands). This pre-crisis Holocene Caspian mollusc community serves as a baseline against which modern mollusc diversity measurements can be evaluated. Examination of faunas from similar environments living today and in the past illustrates the dramatic changes in nearshore communities during the 20th Century. Our study identifies a habitat that may have served as a refuge, but that is currently under threat from invasive species. The severity of the Caspian biodiversity crisis is comparable with other well-known biodiversity crises in semi-isolated ecosystems such as the cichlid fish communities of Lake Victoria, Africa.

This study focuses on the palaeoclimatic evolution and relative sea-level fluctuations of the northern branch of NeoTethys during the late Campanian–early Danian. The studied succession (Ismailler Section) is located in the Mudurnu–Goynuk Basin, NW Turkey and dominated by apparently continuous pelagic muddy deposits. Stable isotopic and elemental compositions of the mudrocks are investigated in order to evaluate the palaeoceanographic conditions as well as broad tectonic reconstruction of the basin. The mudrock geochemistry suggests a tectonic reorganization during late Campanian as reflected by a distinct shift from felsic to mafic sediment provenance. In the Ismailler Section, five δ13C events are identified; four or which are well correlatable with major events in other records around the world, such as the late Campanian Event (LCE), Campanian–Maastrictian Boundary (CMB) and the late Maastrichtian Event (LME). The relative sea-level variations in the basin typically match both short- and long-term global sea-level fluctuations. The remaining globally uncorrelatable δ13C event does coincide with tectonic uplift and the abrupt negative δ13C shift, and is inferred to be the result of regional factors. The dominance of worldwide events in the records of the relatively restricted ocean branch reflects the strength of global factors.

Climate changes close to the Lochkovian-Pragian Event are still widely discussed. Carbonate δ18O and δ13C and conodont apatite δ18O from medial to distal carbonate ramp sediments were analysed to provide further stable isotope data from the stratotype area in the Prague Basin. The uppermost Silurian to lower Emsian δ18O trends are put into an updated conodont biostratigraphy framework. Carbonate δ18O and δ13C are discussed in the context of facies-dependent diagenesis. The δ13C pattern measured from different sections enables the correlation of intervals with development of different facies inside the Prague Basin. Positive δ13C shifts are often coupled with trends of decreasing computed gamma-ray (CGR) values interpreted as regressions, whereas negative δ13C shifts commonly coincide with opposite trends in CGR. The Lochkovian-Pragian boundary interval coincided with an increase in carbonate δ13C and an increase in the δ18O of conodont apatite and carbonate, which we interpret as consequence of climate cooling. Generally, the Lochkovian was warmer than the Pragian and earliest Emsian.

Inoceramid prisms are among the most common microfossils that can be found in Late Cretaceous strata. Since these biomineral units were formed by sequential accretion in the outer shell layer of the bivalves, they potentially serve as archives of short-term (circa-annual) paleowater temperature fluctuations. In the present study, we tested to what extent intra-prismatic stable isotope variations of individual inoceramid prisms reflect sub-annual δ13C and the δ18O patterns. We obtained multiple carbonate samples from prisms recovered from the sediment and from a cross-sectioned inoceramid shell fragment and compared data from these samples to data from classical sclerochronological sampling (i.e., sequential drilling). The analyzed shell material belonged to the species Platyceramus platinus from the Smoky Hill Chalk Member (Niobrara Formation, Kansas, USA). Scanning electron microscopy (SEM) was used to evaluate the diagenetic alteration of the studied prisms and allowed to identify suitable material for stable isotope analyses. The δ18O values of drilled carbonate samples (δ18ODrill) and of prisms (δ18OIP) compare very well to each other when temporally aligned (R2 = 0.98). The stable carbon isotope values (δ13CDrill; δ13CIP), however, show less agreement (R2 = 0.28), which is likely attributable to different time-averaging of the samples. We discuss how to identify the most suitable prisms for sub-annual paleotemperature reconstructions from disarticulated material using microgrowth patterns and geometrical features of the prisms as proxies for changing growth rates. Finally, we apply the novel sampling strategy to naturally occurring disarticulated prisms from the sediment and compare their intra-prismatic isotope values (δ13CIPS and δ18OIPS) to those of bulk-analyzed prism fragments from the sediment (δ13CBPS and δ18OBPS). Sclerochronological analysis of the prisms from the sediment yields δ18OIPS fluctuations of 1.89‰, virtually identical to the δ18OIP chronologies of the prisms extracted from the shell cross-section (1.90‰). The overall ranges of the δ18OIP and δ18OIPS values are identical (2.60‰) and capture very well the expected seasonal stable oxygen isotope oscillation derived from the δ18ODrill values (2.61‰). The range of the δ18OIPS data is two-fold larger than that of the δ18OBPS values (1.19‰), suggesting a strong effect of time-averaging on the stable oxygen isotope data of the bulk-analyzed prisms fragments. According to our novel statistical model, the resolution of δ18OBPS data can be increased by preferentially analyzing short (ca. 300 μm) individual prisms fragments (at least n = 20).

International audience; Planktonic foraminifer tests are major archives of environmental change and provide a multitude of proxies in paleoceanography and paleoclimatology. The application of such proxies is contingent upon a collaborative effort to better understand how the living organisms record the properties of their environment and how the resulting signals are recorded in marine sediments. In this contribution, we provide a review of the rapidly developing sub-fields of research, where new advances have been made possibleby technological developments, and by cross-disciplinary work of the scientific community. Following brief historical overviews of the sub-fields, we discuss the latest advances in planktonic foraminifer research and highlight the resulting new perspectives in ocean and climate research. Natural classification based on consistent species concepts forms the basis for analysis of any foraminifer-derived proxy. New approaches in taxonomy and phylogeny of Cenozoic planktonic foraminifers (Section 2) are presented, highlighting new perspectives on sensitivity and response of planktonic foraminifers to the changing climate and environment (Section 4). Calibration of foraminifer-specific data and environmental parameters is improving along with the technical development of probes and the access to samples from the natural environment (Section 3), enhancing our understanding of the ever-changing climate and ocean system. Comprehension of sedimentation and flux dynamics facilitates maximum gain of information from fossil assemblages (Section 5). Subtle changes in the physical (e.g., temperature), chemical (e.g., pH), and biological (e.g., food) conditions of ambient seawater affect the abundance of species and composition of assemblages as well as the chemical composition of the foraminifer shell and provide increasingly-detailed proxy data on paleoenvironments (Section 6).

The South Atlantic Aptian ‘Pre-salt’ reservoirs are formed by a combination of spherulitic carbonates and Mg-rich clays accumulated in volcanic alkaline lake settings with exotic chemistries. So far, outcrop analogues characterised by metre-thick successions deposited in lacustrine scenarios are elusive so disentangling the genesis of spherulitic carbonates represents a major scientific challenge with business impact. In particular the controls on spatial distribution and the environment of spherulitic facies formation remain poorly constrained, little studied, and hotly debated. To shed light on this conundrum, a spherulitic carbonate-rich, alkaline volcanic lacustrine succession has been analysed at outcrop scale: the Carboniferous East Kirkton Limestone (Scotland). Despite clays being very scarce and limited to layers of amorphous Mg-Si minerals, a diverse array of spherulitic calcitic components were formed, including coated grains, crusts, and build-ups. This setting enables the mechanisms of spherulitic calcite development and the patterns of sediment accumulation to be explored in a geobiological and hydrochemical scenario similar to the ‘Pre-Salt’ subsurface occurrences but divorced from clay influence. The integration of logs, borehole data, outcrop photomosaics and petrographic observations collectively allowed the reconstruction of a depositional model for the East Kirkton lacustrine succession. In this model, calcite spherule nucleation took place at the sediment-water interface in the littoral zone, driven by the co-occurrence of 1) high alkalinity, 2) Ca-Mg rich hydrochemistry, and 3) microbial-derived colloidal exopolymeric substances. These environmental conditions permitted the coeval development of spherulitic cementstone build-ups and spherulitic grainstone-packstone within the wave-agitated zone, and the accumulation of floatstones and laminites of spherulitic grains in deeper lake regions by means of downslope reworking. This model is consistent with the previously documented microbial bloom occurrences and highlights the need to better understand the complex ‘microbe-solution’ interactions before any reliable facies model is envisaged.

The shallow-marine carbonate rocks of the Jandaíra Formation have been subject to significant permeability variations through time due to various events of fracturing and calcite cementation. As a consequence, the Jandaíra Formation accommodated fluid flow only during specific moments in time. We reconstructed these episodes of fluid flow based on isotope characterizations and microscope characteristics of calcite veins and host rock cements. The Jandaíra Formation, which belongs to the post-rift sequence of the Potiguar Basin in northeast Brazil, was deposited from the Turonian onward until a marine regression exposed it in the Campanian. Due to the subaerial exposure, meteoric waters flushed out marine connate waters, leading to an event of early diagenesis and full cementation of the Jandaíra Formation. Fluid flow through the resulting impermeable carbonate formation appears to be closely related to fracturing. Fracturing in the Late Cretaceous induced a drastic increase in permeability, giving rise to extensive fluid circulation. Host rock dissolution associated to the circulating fluids led to calcite vein cementation within the fracture network, causing it to regain an impermeable and sealing character. In the research area, fluid flow occurred during early burial of the Jandaíra Formation at estimated depths of 400–900 m. This study documents the first application of fluid inclusion isotope analysis on vein precipitates, which allowed full isotopic characterization of the paleo-fluids responsible for calcite vein cementation. The fluid inclusion isotope data indicate that upwelling of groundwater from the underlying Açu sandstones provided the fluids to the fracture network. In Miocene times, renewed tectonic compression of a lower intensity created a secondary fracture network in the Jandaíra Formation. The density of this fracture network, however, was too low to induce a new episode of fluid circulation. As a result, this tectonic event is associated with the development of barren extensional fractures.

Stable isotope analysis of marine skeletal carbonates is an important tool for palaeoenvironmental reconstructions. However, in Mesozoic sedimentary sequences, diagenetic alteration often overprints the original skeletal carbonate isotope values. Yet, even if carbonate diagenesis did occur in such sequences, the original oxygen isotope values can still be preserved in enamel or bone phosphate of vertebrate fossils. Here are analysed the isotope compositions of tooth enamel structural carbonate and phosphate of various late Maastrichtian and early Palaeocene shark and ray taxa, as well as carapace bone of a late Maastrichtian marine turtle, Allopleuron hofmanni, from the type area of the Maastrichtian Stage in the southeast Netherlands and northeast Belgium. No correlation is observed between δ18Osc and δ18Op, suggesting diagenetic alteration of at least one fraction. In comparison to modern shark teeth, oxygen isotope ratios of the Maastrichtian–Palaeocene structural carbonate (δ18Osc) are significantly lower (5‰). As expected from previous isotope studies of calcitic fossils from the Maastrichtian type area, we believe the δ18Osc values to have been altered by meteoric diagenesis. The oxygen isotope ratios of phosphate (δ18Op) in Maastrichtian–Palaeocene shark and ray teeth are relatively wide ranging (16.9‰ to 25.0‰ vs. VSMOW), with median values matching data for extant shark teeth δ18Op, suggesting retention of the in vivo δ18Op signal. Similarly, the δ18Osc in the cheloniid turtle A. hofmanni is apparently overprinted by meteoric diagenesis, while the cortical (compact) bone of the carapace is interpreted to reflect the in vivo δ18Op isotope composition. Using a phosphate–water fractionation equation for biogenic apatite and median isotope values of late Maastrichtian–early Palaeocene shark and ray teeth, a seawater temperature of 19.7 °C is calculated. This is in good agreement with temperatures expected for the Maastrichtian of this area. Carbon isotope analyses (δ13C) of structural carbonate in shark teeth have yielded isotope ratios that agree well with those of modern subtropical sharks, suggesting the in vivo carbon isotope signal to have been retained. A comparison of A. hofmanni bone carbonate δ13C values with those of extant marine turtle species, suggests A. hofmanni to have had a carnivorous lifestyle. Also, A. hofmanni shows δ13C values that are > 10‰ lower than the average δ13C of sharks and rays, more similar to sympatric mosasaurs. This distribution is interpreted to be the effect of respiratory physiology on δ13C fractionation.

We present growth incremental stable isotope records (δ18O and δ13C) of modern and ~ 2 Ma fossil bivalve shells from the semi-arid Turkana Basin (N. Kenya, S. Ethiopia). These data suggest that seasonal cyclicity in δ18O and δ13C recorded by modern and fossil shells is driven by wet–dry seasonal changes in host water chemistry, forced by monsoonal rainfall over the Ethiopian Highlands. Fully lacustrine shells show lower amplitude, or even absent seasonal cyclicity in comparison with deltaic or riverine shells because of the buffering effect of the large water volume in the lake setting. Riverine shells arguably have the clearest relation to seasonally variable climate parameters. Riverine molluscs thus provide a potentially valuable proxy for varying rainfall δ18O values in the Turkana Basin catchment. Cross plots of molluscan δ18O and δ13C data reveal dominant environmental control on molluscan isotope values with remarkably large isotopic differences between lacustrine, deltaic and riverine environments. We interpret this isotope pattern to directly result from the different mixing proportions of Omo River source water with evaporated lake water in these environments. The interpretation of fossil molluscan δ18O and δ13C data in a palaeoclimatological context is not straightforward, since the potential influence of temporal changes in lake water temperature, surface evaporation or river discharge on the δ18O budget of the lake is smaller than the isotopic shifts caused by shifting facies patterns in the sedimentary record. Even though it is clear from the rich molluscan faunas that the ~ 2 Ma palaeo-Lake Lorenyang must have been significantly less alkaline than modern Lake Turkana and likely provided good drinking water and abundant availability of food for the different species of hominins inhabiting the region at that time, stable isotope values of molluscan bivalves are not suitable to record the difference in alkalinity between these two settings.

An oxygen isotope record from a stalagmite that grew between 77 ka and 6 ka in northeast Turkey contains both a strong precessional signal, and sub-orbital oscillations similar to those in Greenland ice cores and Chinese speleothem records of monsoon intensity. Fluid inclusion evidence of a negative shift in the isotopic composition of dripwater during the Lateglacial supports interpretation of the isotope curve as an insolation-forced record of changes in rainfall seasonality. The high-amplitude millennial-scale fluctuations are caused by rapid changes in rainfall seasonality and/or switching of moisture source areas, both of which are associated with the stadial-interstadial climatic oscillations linked to the changing modes of the North Atlantic meridional overturning circulation (MOC). Winter rainfall maxima in northeast Turkey coincide with interstadial conditions in Greenland and with periods of intensified Asian monsoon activity. The isotopic shifts in the record are in antiphase with, and are generally much larger in amplitude than, published data from stalagmites in northwest Turkey, most likely because of differing moisture source areas. Carbon isotope ratios are probably kinetically enriched by partial degassing of seepage water in the epikarst, but although often difficult to decypher, particularly during Marine Isotope Stage (MIS) 2, broadly support the interpretations of the oxygen data. © 2012 Elsevier Ltd.

We have applied a new technique to analyze the oxygen (δ18O) and hydrogen (δD) isotope ratios in speleothem fluid inclusions to reconstruct the temperature and rainfall history of southern Indonesia during the Younger Dryas (YD) event and the Holocene. The 12,640-year speleothem record, anchored by 33 uranium-series dates, shows that fluid-inclusion δ18O values vary in phase with speleothem calcite δ18O during the Holocene, suggesting that the speleothem calcite δ18O primarily reflects variations in the δ18O of local rainfall. Significant early to mid-Holocene decreases in both δ18O series are interpreted as an intensification of Australian–Indonesian summer monsoon rainfall in response to deglacial eustatic sea-level rise and flooding of the Sunda Shelf. Cave drip-water temperatures reconstructed from coupled measurements of δ18O in speleothem calcite and fluid inclusions remained relatively constant through the Holocene. This is consistent with reconstructions of Indo-Pacific sea-surface temperature (SST) based on analysis of Mg/Ca ratios in planktonic foraminifera. However, during the YD event, drip-water (i.e. cave) temperature was ∼ 5 °C cooler than modern, which is substantially cooler than SSTs inferred from foraminiferal Mg/Ca, but consistent with coral Sr/Ca reconstructions of SST and terrestrial evidence for high-elevation snow-line depressions. Lower fluid-inclusion δ18O values during the YD indicate that the cooling was accompanied by increased monsoon rainfall. Taken together, the results suggest that the southerly penetration of the intertropical convergence zone (ITCZ) was largely influenced by the cross-equatorial temperature gradient, rather than local SSTs (and air temperatures). Our results provide new evidence for a rapid cooling of deep tropical air temperatures and repositioning of the ITCZ during the YD event.

Temperature reconstructions across Heinrich stadials 1–3 are presented from an absolute-dated speleothem from Abaco Island in the Bahamas to understand the nature of climate change across these intervals in the subtropical Atlantic. The stalagmite carbonate record, dated by the U–Th geochronometry technique, includes higher δ18O and δ13C values within Heinrich stadials 1, 2, and 3 followed by rapid declines at the end of the stadials. To aid in the interpretation of these results, the δ18O of fluid inclusions associated with the Heinrich stadials were also analyzed. These measurements, which allowed for the relative influence of temperature and δ18O of precipitation to be distinguished, demonstrate minimal changes in the δ18O of fluid inclusions, suggesting that changes in the δ18O values of the speleothem carbonate associated with Heinrich stadials 1–3 are principally driven by an average ∼ 4 ° C temperature decrease, rather than a change in the δ18O of the rainfall (hence rainfall amount). These findings support previous work in the North Atlantic and are consistent with the climate response to a weakening of the Atlantic meridional overturning circulation.

6 p. Modern and fossil freshwater bivalves from north-eastern Peru are investigated to reconstruct seasonal rainfall patterns in Miocene Amazonia. Oxygen isotope variation in incremental growth bands of fossil bivalves reflects past hydrological conditions in the Miocene Climate Optimum (MCO), when the world was warmer than today. A calibration experiment was conducted on a modern bivalve. Modern river dwelling Triplodon corrugatus shows large amplitudinal changes in d18O, which mirror the seasonal variation in rainfall as a result of the annual migration cycle of the Inter Tropical Convergence Zone (ITCZ). Growth incremental oxygen isotope records of Miocene Amazonian Diplodon aff. Longulus bivalves show strikingly similar patterns. This suggests that the seasonal migration of the ITCZ and the intensity of the hydrological cycle in the MCO were comparable to today. The implications are that humid climate conditions sufficient to sustain a rainforest ecosystem already existed ~16 Ma ago.

A two-box ocean model with a coupled carbon and phosphorus cycle is used to test which processes can realistically generate a rapid positive 2‰ δ13C excursion in the global carbon reservoir. Internal oceanic processes (enhanced preservation of organic matter under anoxic conditions, enhanced upwelling) cannot produce a substantial δ13C excursion under the assumption that burial rates of C and P are coupled. Loss of nutrients to the sediment acts as a negative feedback mechanism that prevents a substantial perturbation of the carbon cycle. A large and renewable source of nutrients is needed, either from increased continental weathering or from enhanced regeneration of sedimentary organic phosphorus under anoxic conditions. Measurements of total phosphorus and organic carbon in sediments from the Tarfaya Basin, Morocco, suggest that a large decrease in P burial occurred relative to organic carbon at the base of the Cenomanian–Turonian Oceanic Anoxic Event (OAE2), with the right magnitude to quantitatively explain a 2‰ shift in δ13C. It is concluded that the main underlying mechanism that allowed and sustained enhanced carbon burial during the mid-Cretaceous was a perturbation of the oceanic phosphorus cycle.

In a floodplain lake of the Amazon River near the city of Iquitos, northeastern Peru, a one-year monitoring experiment was conducted during which water samples and living bivalves (Anodontites trapesialis) were collected with the aim to investigate seasonal δ18O variation in and fractionation between bivalve aragonite and host water. Both host water and molluscan growth increments show more than 8‰ seasonal variation in δ18O. In the floodplain lake under study the δ18O variation of the water is controlled by contrasting dry and wet season evaporation–precipitation regimes. Molluscan δ18O appears to be in equilibrium with the host water. Although an approximately 4.0‰ offset occurs, δ13C records of water and bivalves are in good agreement, suggesting that both δ18O and δ13C of the shells of freshwater bivalve A. trapesialis are good recorders of (palaeo-)environmental conditions. The δ13C of Dissolved Inorganic Carbon (DIC) is governed by plant growth and/or by changes in aquatic chemistry, affecting the DIC pool.

Discontinuity surfaces that recorded superposition of marine hardground and subaerial exposure stages are common in the Middle Cretaceous of northern Oman. These surfaces formed during periods of rapid sea-level drop. The marine hardground stages are dominant in the field, whereas the subaerial exposure stage is documented in circumstantial petrographic, geochemical, and biological evidence. The record of a shoaling phase prior to exposure is commonly subtle and incomplete; supratidal deposits are conspicuously absent. Porosity in the limestones underlying the discontinuities is rearranged during subaerial exposure and subsequent burial and hence the permeability of large volumes of limestone is affected at a variety of scales. During marine hardground stages, carbonate cements, iron oxides, and manganese occludes some of the existing pore space. During burial, these intervals may thus have acted as either seals or efficient conduits of fluid flow. The surfaces under study in the Shu’aiba, Nahr Umr, and Natih formations are spaced ten to few tens of meters apart and many of them were traced laterally over distances of 100 kilometers and more between sections at Jebel Akhdar and in the Foothills. This implies that they play an important, but poorly understood role in compartmentalization of carbonate reservoir rocks.

Strontium isotopic ratios and Sr contents of molluscs from the Miocene Pebas Formation in Colombian Amazonia indicate that the bulk of the Pebas Formation was deposited in a freshwater environment, predominantly draining the Andes, with minor contribution from the shield regions. The molluscan oxygen and carbon isotopic composition does not provide a palaeosalinity proxy, but points to a lacustrine palaeoenvironment. The faunal character confirms such an interpretation. Sr isotopic ratios further suggest that a marine incursion that reached the area was composed of a mixture of shield-derived freshwater and seawater, with a maximum salinity of about 5 psu. Faunistic components of this incursion-level support a shield–seawater mixing. The incursion most likely reached western Amazonia from the north, probably along the western Guyana shield.

International audience; Dansgaard-Oeschger (D-O) cycles were the most prominent, abrupt climate events of the last glacial period whose impact was most strongly felt in the high latitudes of the North Atlantic region. The climate links between the North Atlantic, the Asian and American tropics, and Antarctica during these cycles are well documented. However, the potential role of the Indo-Pacific Warm Pool and Australasian monsoon system in propagating climate impacts across the hemispheres is still unclear. Here, we use tandem measurements of oxygen isotopes in calcite and fluid inclusions, as well as carbon-isotope ratios, from multiple stalagmites from Liang Luar Cave, Flores (southern Indonesia) to examine the monsoon response to D-O event number 21 (~87,000-84,000 years ago), the longest and warmest event recorded in Greenland ice cores. The record shows that there was a rapid decline in monsoon rainfall in Indonesia during D-O21 warming in Greenland and cooling in Antarctica. At around the same time, the East Asian monsoon was intensified, indicating that the intertropical convergence zone (ITCZ) shifted abruptly to the north during this event. Our record also shows that there was a 2-3 °C increase in local air temperature, which would have acted to increase primary productivity and promote the generation of soil carbon for methanogenesis. Therefore, our findings indicate that ITCZ positioning in tropical Australasia--through its influence on large-scale oceanic-atmospheric circulation--played a key role in transmitting the abrupt climate signal between the hemispheres, thereby facilitating the rapid rise of atmospheric CO2 and CH4 concentrations during D-O21 that ultimately led to global warming and the demise of the MIS5b stadial.

In the light of the currently increasing drought frequency and water scarcity on oceanic islands, it is crucial for the conservation of threatened insular vertebrates to assess how they will be affected. A 4000 yr old fossil assemblage in the Mare Aux Songes (MAS), southwest Mauritius, Mascarene Islands, contains bones of 100 000+ individual vertebrates, dominated by two species of giant tortoises Cylindraspis triserrata and C. inepta, the dodo Raphus cucullatus, and 20 other vertebrate species (Rijsdijk, Hume, Bunnik, Florens, Baider, Shapiro et al. (2009) Mid-Holocene vertebrate bone Concentration-Lagerstätte on oceanic island Mauritius provides a window into the ecosystem of the dodo (Raphus cucullatus). Quaternary Science Reviews 28: 14-24). Nine radiocarbon dates of bones statistically overlap and suggest mass mortality occurred between 4235 and 4100 cal. yr BP. The mortality period coincides with a widely recognized megadrought event. Our multidisciplinary investigations combining geological, paleontological and hydrological evidence suggests the lake was located in a dry coastal setting and had desiccated during this period. Oxygen isotope data from a Uranium-series dated stalagmite from Rodrigues, an island 560 km east of Mauritius, supports this scenario by showing frequently alternating dry and wet periods lasting for decades between 4122 and 2260 cal. yr BP. An extreme drought resulted in falling water-tables at MAS and elsewhere on the island, perhaps deprived these insular vertebrates of fresh water, which led to natural mass mortalities and possibly to extirpations. In spite of these events, all insular species survived until at least the seventeenth century, confirming their resistance to climatic extremes. Despite this, the generally exponential increase of combined human impacts on islands including loss of geodiversity, habitats, and stocks of fresh water, there will be less environmental safe-haven options for insular endemic and native vertebrates during future megadrought conditions; and therefore will be more prone to extinction. Corrigendum: The title of this article should refer to 4200 yr BP rather than 4200 kyr BP. The title should read as follows: Mid-Holocene (4200 yr BP) mass mortalities in Mauritius (Mascarenes): insular vertebrates resilient to climatic extremes but vulnerable to human impact

By means of a monitoring experiment in two rivers in the Netherlands, we establish a relationship between seasonally resolved growth rates in unionid freshwater bivalves and their environment. We reconstructed these seasonally resolved growth rates by using relationships of stable isotopes in the shells and their ambient river water. The reconstructed growth rates reveal that shells grow fastest in spring-early summer, when highest food availability occurs in the rivers. In addition, the reconstructed growth rates show that onset and cessation of growth are mainly influenced by water temperature.

The application of oxygen isotope ratios (δ18O) from freshwater bivalves as a proxy for river discharge conditions in the Rhine and Meuse rivers is investigated. We compared a dataset of water temperature and water δ18O values with a selection of recent shell δ18O records for two species of the genus Unio in order to establish: (1) whether differences between the rivers in water δ18O values, reflecting river discharge conditions, are recorded in unionid shells; and (2) to what extent ecological parameters influence the accuracy of bivalve shell δ18O values as proxies of seasonal, water oxygen isotope conditions in these rivers. The results show that shells from the two rivers differ significantly in δ18O values, reflecting different source waters for these two rivers. The seasonal shell δ18O records show truncated sinusoidal patterns with narrow peaks and wide troughs, caused by temperature fractionation and winter growth cessation. Interannual growth rate reconstructions show an ontogenetic grow...

At Ocean Drilling Program Site 689 (Maud Rise, Southern Ocean), δ18O records of fine-fraction bulk carbonate and benthic foraminifers indicate that accelerated climate cooling took place following at least two closely spaced early late Eocene extraterrestrial impact events. A simultaneous surface-water productivity increase, as interpreted from δ13C data, is explained by enhanced water-column mixing due to increased latitudinal temperature gradients. These isotope data appear to be in concert with organic-walled dinoflagellate-cyst records across the same microkrystite-bearing impact-ejecta layer in the mid-latitude Massignano section (central Italy). In particular, the strong abundance increase of Thalassiphora pelagica is interpreted to indicate cooling or increased productivity at Massignano. Because impact-induced cooling processes are active on time scales of a few years at most, the estimated 100 k.y. duration of the cooling event appears to be too long to be explained by impact scenarios alone. This implies that a feedback mechanism, such as a global albedo increase due to extended snow and ice cover, may have sustained impact-induced cooling for a longer time after the impacts.

Paleobiologists tend to use dietary information as an ecological indicator because diet is a fundamental link between an organism and its environment. However, the ecological information from fossilized hard tissues is often difficult to interpret, because links between environment, diet, and hard tissue biology are insufficiently studied in modern communities. To address this dilemma, we investigated dietary proxies commonly used by paleobiologists in a 4-ruminant community from the French Alps. Dental microwear texture analyses are applied to 82 specimens of roe deer, red deer, chamois, and mouflons. Intra-tooth serial enamel stable carbon and oxygen isotope analyses of the structurally bound carbonate were applied on eleven specimens, with isotope-based niche reconstructions, and inverse modeling of original seasonally variable oxygen isotope inputs. While microwear complexity largely overlaps, both inter-individual dispersion of complexity and individual heterogeneity of complexity together with the anisotropy track dietary differences. The red deer is likely more engaged in grazing than the two bovids, which both plot as mixed feeders. When combined, dental microwear texture and carbon stable isotope analyses accurately reflect known ecological separation between the chamois and the roe deer. Both stable isotopes suggest niche separation by increasing enrichment from roe deer to red deer, to chamois; mouflons appear to feed as generalists. In roe deer, which shows the highest enamel oxygen isotope range (5.7‰), variation is nevertheless constrained compared to oxygen isotope ranges observed in regional precipitation, where the mean annual range reaches 9.9‰. However, through inverse modeling we estimate seasonal input ranges that average 9.7‰, a result strikingly similar to regional values. Altogether, our data demonstrate that given appropriate sampling strategies and modeling approaches, microwear and isotopic data can be effective tools for demonstrating niche separation among multiple sympatric herbivorous taxa.