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The long-term global cooling trend during the latest Cretaceous was interrupted by an intense global warming episode at ~69 Ma known as the mid-Maastrichtian event (MME). The MME is characterized by two positive 13C excursions with an overall magnitude of 0.6‰ to 1.5‰ separated by a negative inflection. The 13C excursions are accompanied by the extinction of inoceramid bivalves, an abrupt increase in deep-sea and sea-surface temperatures as well as terrestrial mean annual temperatures between 21 and 23 °C at a paleolatitude of ~35° N. Changes in oceanic circulation, particularly a change in thermohaline circulation patterns, have been identified to be one of the main drivers of the MME. Nevertheless, the driving mechanisms, timing, character, and consequences of the circulation change are still up for debate. In this study, a 2 Myr-long time interval of the Mid to Late Maastrichtian has been analyzed at a ~2.5 to 5 kyr-resolution with the aim to improve the understanding of the climatic patterns leading to the MME. For IODP Core U1403 in the North Atlantic (J-Anomaly Ridge), XRF core scanning, wt% CaCO3 analyses, and stable oxygen and carbon isotope records of benthic foraminifera were generated. Bottom-water temperatures were reconstructed through Mg/Ca measurements of the same foraminiferal tests. Preliminary data reveal a warming of North Atlantic deep-sea temperatures by ~2–3°C between ~68.5 and 69 Ma, accompanied by several CaCO3 dissolution events as well as 13C excursions of up to 0.8 ‰. These findings point towards a major perturbation in the global carbon cycle accompanying the overall change in ocean circulation whose causes appear to be more complex than previously thought.

Citizen science (CS) can foster transformative impact for science, citizen empowerment and socio-political processes. To unleash this impact, a clearer understanding of its current status and challenges for its development is needed. Using quantitative indicators developed in a collaborative stakeholder process, our study provides a comprehensive overview of the current status of CS in Germany, Austria and Switzerland. Our online survey with 340 responses focused on CS impact through (1) scientific practices, (2) participant learning and empowerment, and (3) socio-political processes. With regard to scientific impact, we found that data quality control is an established component of CS practice, while publication of CS data and results has not yet been achieved by all project coordinators (55%). Key benefits for citizen scientists were the experience of collective impact (“making a difference together with others”) as well as gaining new knowledge. For the citizen scientists’ learning outcomes, different forms of social learning, such as systematic feedback or personal mentoring, were essential. While the majority of respondents attributed an important value to CS for decision-making, only few were confident that CS data were indeed utilized as evidence by decision-makers. Based on these results, we recommend (1) that project coordinators and researchers strengthen scientific impact by fostering data management and publications, (2) that project coordinators and citizen scientists enhance participant impact by promoting social learning opportunities and (3) that project initiators and CS networks foster socio-political impact through early engagement with decision-makers and alignment with ongoing policy processes. In this way, CS can evolve its transformative impact., Socio-Ecological Practice Research, 5 (1)

The Eocene, as the warmest epoch during the Cenozoic, has received much attention as it can inform us about the features of global warmth, highly relevant to a “high-CO2” future. However, there is still a lack of knowledge regarding some key features of global warm climates, such as how higher global temperatures might have affected the duration and intensity of seasonality. Furthermore, recognizing seasonal cycles is essential when interpreting proxy data and reconstructing paleo climate, e.g. in order to understand inter-annual bias between proxies. In the current study the seasonal variations in sea surface temperature (SST) and fresh water input into the Anglo-Paris Basin (subjacent areas of the Paleo-North Sea) was investigated. Marginal seas, like the Paleo North Sea, are an important intersection between the continental and marine realm, and are especially sensitive to short-term climate variations.In order to resolve seasonal and perennial changes in SST and freshwater balance, we measured Ba/Ca, δ18O, and the clumped isotopic composition (∆47) of exceptionally well-preserved fossil molluscs. Although δ18O is commonly used for the reconstruction of temperature, its calculation often assumes a constant δ18O value of seawater, which might not be true on seasonal scales and/or within swallow marine basins. In this context, ∆47 was employed to determine the average temperature amplitude, due to its independence from δ18Oseawater. Additionally, Ba/Ca was used to account for periods with enhanced fresh water input, because barium mostly enters the oceans via fluvial systems and could therefor indicate seasonally enhanced and isotopic lighter fresh water input. The bivalve species Venericor planicosta was employed as proxy archive, due to its long life span (10-20 years) and its wide distribution in the Anglo-Paris Basin during the Eocene. The pristinely preserved, aragonitic bivalve shells were sampled by micro-milling (δ18O, ∆47), as well as, laser ablation (Ba/Ca), to generate proxy records with high temporal resolution.The isotopic data reveal well pronounced seasonal oscillation with a sinusoidal shape and a maximum difference of 2‰, from -3,5‰ to -5,5‰. On average, the inter-annual variation of the δ18O record is around 1‰. The Ba/Ca record, on the other hand, shows a flat background with recurring large and sharp peaks. While the baseline Ba/Ca values are around 20 µmol/mol, the peaks can reach up to 300 µmol/mol. The peaks largely fall together with periods of depleted δ18O values. These results hint to a possible seasonal bias of temperature records in the Anglo-Paris basin based purely on δ18O, due to variable δ18O of seawater. This is further implied by the back-calculation of δ18Oseawater from ∆47 measurements, revealing a range from 2‰ to -4‰.

The late Cretaceous climate is represented by an 8-10 °C decline of global mean temperatures that terminated global warmth of mid-Cretaceous times. Causal mechanisms of the cooling are still not well constrained and discussed in the interplay of reduced volcanic greenhouse gas emission and intensified silicate weathering as a global carbon cycle feedback. The lithium isotopic composition (δ7Li) of marine carbonates is a proxy for the chemical weathering intensity of silicate rocks, and thus provides information about the role of silicate weathering as thermostat and sink for atmospheric CO2.Here, we present the first detailed chalk-derived Late Cretaceous δ7Li record (91-66 Ma) of the boreal white chalk in Northern Germany (Lägerdorf-Kronsmoor-Hemmoor) and from sections in southern England as archive for the seawater lithium isotopic composition. In the course of this study, we will also analyze the archives of skeletal calcite from brachiopods, belemnites and rudists, which should enable us to identify systematic offsets among different calcifiers related to vital effects by the direct comparison of fossilized shells and their surrounding sediments.To handle the potential impact of clay contamination in bulk carbonates, we applied a pre-leaching and leaching procedure with 1 M ammonium acetate and 0.05 M nitric acid. The method was tested for a 1.85 Ma old sample of coccolith ooze from the Manihiki Plateau (equatorial West Pacific Ocean), which has consistent δ7Li values and shows a systematic negative 3-4 ‰ offset to modern seawater. In addition, the degree of potentially leached silicates is monitored by the analysis of E/Ca ratios, like Al/Ca.In total, our late Cretaceous lithium isotope record shows a trend of rising δ7Li values between +16 and +25 ‰. Superimposed, the curve displays a rise in the Santonian, a local maximum in the early Campanian followed by a drop to a local minimum in the late Campanian. Subsequently, the δ7Li values rise again towards elevated values in the Maastrichtian. Overall, the shape of the δ7Li curve strongly resembles the evolution of deep-sea temperatures based on benthic oxygen isotopes suggesting a close link between climate and weathering. Thereby, more positive δ7Li values correspond to cooling periods and the late Campanian lowering of δ7Li values parallels the intermittent deep-sea warming. Such a pattern points towards a strong relationship between the congruency of silicate weathering and climate on a multi-million year time scale.

High-amplitude shifts in sedimentary δ13C characterize the Cretaceous system and have been proven to be of great use for supraregional chemostratigraphic correlation. Here we present an upper Berriasian to lower Coniacian (c. 142 – 88 Ma) composite carbon isotope record based on 14 drill cores, two outcrops and almost 5000 samples. The total record comprises a composite thickness of about 1500 m. All cores and successions are located in the larger Hanover area, which represents the depocenter of the North German Lower Saxony Basin (LSB) in early to mid-Cretaceous times.Boreal Lower Cretaceous sediments are predominantly represented by CaCO3-poor mud- and siltstones of up to 2000 m thickness in northern Germany, which become more carbonate-rich during the Albian-Cenomanian transition and even chalkier in the upper Cenomanian to Coniacian interval. A number of global carbon isotope key events including the Valanginian Weissert Event, the OAEs 1a, b and d (Aptian-Albian) as well as for the early Late Cretaceous the Mid-Cenomanian Event (MCE), the OAE 2 (Cenomanian-Turonian Boundary Event) and the Navigation Event, among others, have been identified allowing for a detailed comparison with Tethyan and other Boreal records. Thus, this new detailed chemostratigraphy provides a unique opportunity to potentially overcome many still existing Boreal–Tethyan correlation issues. The presented record can be considered to be almost complete, albeit a small gap in the early Albian cannot be ruled.

The characteristics of half-precession (HP) cycles (~9,000 - 12,000 years) is still poorly understood, despite their appearance in numerous records. We analyse HP signals in a variety of different marine and terrestrial proxy records from Europe and the Atlantic Ocean, investigate the temporal evolution of the HP signal from the early/middle Pleistocene to the present, and evaluate the potential of the HP to reflect the connectivity of climate systems over time.We apply filters on the datasets that remove the classical orbital cycles (eccentricity, obliquity, precession) and high frequency signals, and focus on the bandwidth of HP signals. Wavelet annalysis and correlation techniques are used to study the evolution of specific frequencies through the different records.In addition to a connection of HP cycles with interglacials, we observe a more pronounced HP signal in the younger part of several proxy records. Besides, we observe a trend of more pronounced HP signals in low latitude records compared to high latitudes. This is in agreement with the assumption that HP is an equatorial signal and can be transmitted northward via various pathways. The appearance of HP signals in mid- and high-latitude records may thus be an indicator for the intensity of the transporting mechanisms. We suggest that the African Monsoon plays a major role in this context, as its magnitude directly influences the climate systems of the Mediterranean and Southern Europe. In order to better understand the African climate variability, both equatorial marine and terrestrial records will be examined with respect to HP.

Global change, including urbanisation, threatens many of the >1400 bat species. Nevertheless, certain areas within highly urbanised cities may be suitable to harbour bat populations. Thus, managing urban habitats could contribute to bat conservation. Here, we wanted to establish evidence-based recommendations on how to improve urban spaces for the protection of bats. In a team effort with >200 citizen scientists, we recorded bat vocalisations up to six times over the course of 2 years at each of 600 predefined sites in the Berlin metropolitan area. For each species we identified the preferred and non-preferred landscape features. Our results show that artificial light at night (ALAN) had a negative impact on all species. For soprano pipistrelles and mouse-eared bats ALAN had the largest effect sizes among all environmental predictors. Canopy cover and open water were especially important for bat species that forage along vegetation edges and for trawling bats, respectively. Occurrence probability of species foraging in open space decreased with increasing distance to water bodies. On a larger scale, impervious surfaces tended to have positive effects on some species that are specialised on foraging along edge structures. Our study constitutes an important contribution to the growing body of literature showing that despite the many negative impacts of urbanisation on wildlife, urban environments can harbour bat populations if certain conditions are met, such as access to vegetation and water bodies and low levels of ALAN. Our findings are of high relevance for urban planners and conservationists, as they allow inferences on how to manage urban spaces in a bat-friendly way. We recommend limiting ALAN to the minimum necessary and maintaining and creating uninterrupted vegetated corridors between areas with high levels of canopy cover and water bodies, in which ALAN should be entirely avoided.

This is the first version of the White Paper Citizen Science Strategy 2030 for Germany. This version is out for consultation from 8/8/21-30/9/2021 and will then be revised with received comments and reviews accordingly. Consultation website: www.citizen-science-weissbuch.de

Cold-water corals (CWC), dominantly Desmophyllum pertusum (previously Lophelia pertusa), and their mounds have been in the focus of marine research during the last two decades; however, little is known about the mound-forming capacity of other CWC species. Here, we present new 230Th/U age constraints of the relatively rarely studied framework-building CWC Solenosmilia variabilis from a mound structure off the Brazilian margin combined with computed tomography (CT) acquisition. Our results show that S. variabilis can also contribute to mound formation, but reveal coral-free intervals of hemipelagic sediment deposits, which is in contrast to most of the previously studied CWC mound structures. We demonstrate that S. variabilis only occurs in short episodes of

The continental expression of global cooling during the Miocene Climate Transition in Central Asia is poorly documented, as the tectonically active setting complicates the correlation of Neogene regional and global climatic developments. This study presents new geochemical data (CaSO4 content, carbonate δ13C and δ18O) from the endorheic alluvial‐lacustrine Aktau succession (Ili Basin, south‐east Kazakhstan) combined with findings from the previously published facies evolution. Time series analysis revealed long‐eccentricity forcing of the paleohydrology throughout the entire succession, split into several facies‐dependent segments. Orbital tuning, constrained by new laser ablation U‐Pb dates and a preexisting magnetostratigraphy, places the succession in a 5.0 Ma long interval in the middle to late Miocene (15.6 to 10.6 Ma). The long‐term water accumulation in the Ili Basin followed the timing of the Miocene Climate Transition, suggesting increased precipitation in the catchment area in response to climate cooling and stronger westerly winds. This was paced by minima of the 2.4 Ma eccentricity cycle, which favored the establishment of a discharge playa (~14.3 Ma) and a perennial lake (12.6 to 11.8 Ma). Furthermore, low obliquity amplitudes (nodes) caused a transient weakening of the westerlies at ~13.7 to 13.5 Ma and at ~12.7 Ma, resulting in negative hydrological budgets and salinization. Flooding of the windward Ili Basin coeval with aridification in the leeward basins suggests that the Tian Shan was a climate boundary already in the middle Miocene. Our results emphasize the impact of climate fluctuations on the westerlies' strength and thus on Central Asian hydrology., Plain Language Summary: The global climate changed from an exceptional warm to a colder state in the middle Miocene epoch, representing a milestone in the evolution of today's climate. This study focuses on the, so far fragmentary, understanding of the Central Asian climate response to this global climate transition by investigating deposits of a former (salt) lake in the Ili Basin, southeast Kazakhstan. Regular sediment alternations represent cycles of low and high water level, overprinted by a long‐term lake expansion. Time series analysis of climate sensitive geochemical and environmental parameters, together with the determination of absolute rock ages, enabled the identification of sedimentary cycles (405 ka and 1.2 Ma long), which are equivalent to climate influencing variations of the Earth's orbit and tilt angle. We conclude that water level maxima are linked to periods of low seasonal climate differences reoccurring every 405 ka. The lake expansion is caused by more precipitation due to strengthened westerly winds, in response to global cooling. Westerly winds were transiently weakened during periods of low variability of the Earth's tilt angle, promoting high evaporation and salinization. Our results emphasize the impact of climate change on the westerlies' strength and thus on Central Asian moisture supply., Key Points: The endorheic Miocene Ili Basin features orbital control of its hydrological budget by long eccentricity and obliquity amplitude modulation. Obliquity amplitude modulation affected the westerlies' strength during the Miocene Climate Transition. The Miocene global cooling led to strengthening of the westerlies reflected by groundwater accumulation and lake expansion in the Ili Basin., Deutsche Forschungsgemeinschaft (DFG) http://dx.doi.org/10.13039/501100001659

The increased aridification of Central Asia during the Miocene coincides in time with lake formations and the evolution of playa environments in the region. However, Miocene continental climate dynamics and the forcing of aridification are still not well constrained. Neogene lacustrine mudflat deposits in the Ili Basin in southeast Kazakhstan provide a well-exposed paleoclimate archive. Here, we present a detailed rock magnetic study of a middle Miocene playa cycle deposited in a closed basin. We use high-resolution rock magnetic parameters, lithological studies and geochemistry to reconstruct the playa environment and the depositional conditions. The rock magnetic mineralogy of the playa cycle is controlled by hematite and two fine-grained magnetite phases. Increased magnetic concentrations occur during dry mudflat conditions, with a lower groundwater table and increased aridity. The underlying processes controlling the observed variation in magnetic concentrations are a complex interplay of diagenetic processes during and after deposition. The data support an authigenic origin of both magnetite phases, one formed before and the other after sediment consolidation. Early diagenetic formation of fine-grained magnetite by microbial activity is followed by post-depositional formation of a secondary fine-grained magnetite phase. The rock magnetic results such as magnetic concentration-dependent parameters, ARM/SIRM and s-ratio indicate a sensitive record of (ground) water availability and aridity changes in the Ili Basin. We suggest that they can serve as an effective proxy for detailed paleo-environment reconstruction of playa evolution, not only in the middle Miocene Ili Basin but also in comparable floodplain/playa lake settings.

Hyrrokkin sarcophaga is a parasitic foraminifer that is commonly found in cold-water coral reefs where it infests the file clam Acesta excavata and the scleractinian coral Lophelia pertusa. Here, we present measurements of the elemental and isotopic composition of this parasitic foraminifer for the first time, analyzed by inductively coupled optical emission spectrometry (ICP-OES), electron probe micro analysis (EPMA) and mass spectrometry (MS).Our results reveal that the geochemical signature of H. sarcophaga depends on the host organism it infests. Sr/Ca ratios are 1.1 mmol mol−1 higher in H. sarcophaga that infest L. pertusa, which could be an indication that dissolved host carbonate material is utilised in shell calcification, given that the aragonite of L. pertusa has a naturally higher Sr concentration compared to the calcite of A. excavata. Similarly, we measure 3.1 ‰ lower δ13C and 0.25 ‰ lower δ18O values in H. sarcophaga that lived on L. pertusa, which might be caused by the direct uptake of the host's carbonate material with a more negative isotopic composition or different pH regimes in these foraminifera (pH can exert a control on the extent of CO2 hydration/hydroxylation) due to the uptake of body fluids of the host. We also observe higher Mn/Ca ratios in foraminifers that lived on A. excavata but did not penetrate the host shell compared to specimen that penetrated the shell, which could be interpreted as a change in food source, changes in the calcification rate, Rayleigh fractionation or changing oxygen conditions.While our measurements provide an interesting insight into the calcification process of this unusual foraminifer, these data also indicate that the geochemistry of this parasitic foraminifer is unlikely to be a reliable indicator of paleoenvironmental conditions using Sr/Ca, Mn/Ca, δ18O or δ13C unless the host organism is known and its geochemical composition can be accounted for.

Lake Ohrid is located on the Balkan Peninsula between Albania and North Macedonia. It is considered Europe’s oldest lake and thus is a valuable archive for studies that focus on the change of local (hydro-)climate during the last 1.36 million years (e.g., Francke et al. 2016; Wagner et al. 2019). During an International Continental Scientific Drilling Program (ICDP) campaign in 2013, geophysical downhole logging by the Leibniz Institute for Applied Geophysics acquired continuous datasets of physical properties. Additionally, 2100 m of sediment core was obtained from different sites, the deepest with a length of 570 m (Wagner et al. 2014).Investigations of half-precession (HP) cycles (~9,000 – 12,000 years) have been given only a small role or have been completely neglected in previous cyclostratographic studies. In this study we focus on HP signals in Lake Ohrid and investigate the temporal variability of this signal over the last one million of years. Next to a connection of HP cycles to interglacials, we see a more pronounced correlation of the HP signal to natural gamma radiation logs in the younger part of the record.We relate the results from Lake Ohrid to a variety of proxy records from the European mainland and marine sediment cores from the Atlantic and the Mediterranean. Certain patterns, such as the increased visibility of the HP signal in interglacials, occur in most records, but differences, like variations in the amplitude modulation of the filtered HP signal, need to be investiagted in more detail. Nevertheless, the HP cycles are contained in all of the investigated sites, although the records are influenced by different climatic systems. This illustrates that HP signals cannot be connected to a certain climatic system, but can occur simultaneously in records with different proxy signal origins.HP cycles are a relevant part of natural climate variability - also in Europe - and allow a more detailed investiagtion of sedimentary systems. References:Francke, A., Wagner, B., Just, J., Leicher, N., Gromig, R., Baumgarten, H., … & Giacco, B. (2016). Sedimentological processes and environmental variability at Lake Ohrid (Macedonia, Albania) between 637 ka and the present, Biogeosciences , 13, 1179–1196.Wagner, B., Wilke, T., Krastel, S., Zanchetta, G., Sulpizio, R., Reicherter, K., …. & Vogel, H. (2014). The SCOPSCO drilling project recovers more than 1.2 million years of history from Lake Ohrid, Sci. Drill. , 17, 19-29.Wagner, B., Vogel, H., Francke, A., Friedrich, T., Donders, T., Lacey, J. H., … & Zhang, X. . (2019). Mediterranean winter rainfall in phase with African monsoons during the past 1.36 million years, Nature , 573(7773), 256-260.

This is the conference programme of the Citizen Science SDG Conference titled "Knowledge for Change: A decade of Citizen Science (2020-2030) in support of the SDGs" that took place on 14.-15. October 2020 as a hybrid conference (in Berlin and online). This conference was an official event of Germany’s 2020 EU Council presidency. The conference took place as part of the CS-SDG project, which has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 101000014.

This is the abstract volume of the Citizen Science SDG Conference titled "Knowledge for Change: A decade of Citizen Science (2020-2030) in support of the SDGs" that took place on 14.-15. October 2020 as a hybrid conference (in Berlin and online). This conference was an official event of Germany’s 2020 EU Council presidency. The conference took place as part of the CS-SDG project, which has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 101000014.

The Data Management Plan outlines the details and procedures for how to handle data generated in the CS-SDG project according to the relevant aspects of making data FAIR, including which data the project will generate, whether and how it will be made accessible for verification and reuse, and how it will be curated and preserved.

Phytoplankton is one of the most important producers of oxygen, and plays an important role in the export of large amounts of carbon to the deeper ocean. Since phytoplankton is also the basis of most food webs in the ocean, understanding the dynamic system of phytoplankton is a crucial part to understand past carbon- and nutrient cycles and paleoclimatic changes. The export of nutrients is also an important factor impacting cold-water coral (CWC) reefs and may play a role in controlling their distribution. Here we present laser ablation inductively coupled mass spectrometer (LA-ICP-MS) Element/Ca measurements from Acesta excavata, a file clam, often associated with cold-water coral reefs along the European continental margin. Environmental parameters were recorded with lander systems directly deployed in the CWC reefs, which allows us to compare our geochemical data to in-situ ocean data.Our results reveal, that Ba/Ca ratios show stable baseline values with intermittent sharp peaks. The location of these peaks in between major growth lines and temperature reconstructions with Mg/Sr ratios (Schleinkofer et al., submitted) show that these peaks occur during Winter and are repeatable between samples from the same location. This indicates a strong external forcing mechanism and allows cross-dating of different bivalve shells. While the occurrence of Ba/Ca peaks correlates with phytoplankton maxima, the absolute Ba/Ca ratio does not correlate with the phytoplankton abundance.Mn/Ca ratios show similar trends as Ba/Ca ratios but the peaks are phase shifted and occur slightly delayed. These peaks could be triggered by decreasing oxygen concentrations in the water caused by the decomposition of organic material.As A. excavata does not show easily distinguishable growth lines under the light microscope despite of Mutvei staining or fluorescence microscopy, we hypothesize that P/Ca ratios might be usable to locate highly phosphorylated shell areas that usually correlate with major growth lines. P/Ca ratios show no perceivable features in the vicinity of major growth lines. Instead we recognize that Ba/Ca peaks follow a minimum in P/Ca which is possibly caused by the uptake of phosphor by plankton.These results suggest that A. excavata have potential as a promising tool for high resolution paleoenvironmental reconstructions of both intermediate and overlying surface water masses.ReferencesSchleinkofer N, Raddatz J, Evans D, Gerdes A, Flögel S, Voigt S, et al. Elemental to calcium ratios in the marine bivalve Acesta excavata: an archive for high-resolution paleoceanographic reconstructions of intermediate water masses. PLoS One. Submitted

Hydrological extremes related to the South American Summer Monsoon (SASM) are expected to become more frequent in the near future and might have devastating socioeconomic consequences for the densely populated region of eastern Brazil. Given the complexity in SASM behaviour in space and time, a dense coverage of monsoonal precipitation records, particular those spanning multiple glacial-interglacial cycles, are urgently needed to constrain this high spatial-temporal variability. This information is necessary to reduce the uncertainty associated with projections of SASM precipitation in response to rising anthropogenic greenhouse gas (GHG) emissions. Here we use elemental ratios from X-ray fluorescence scanning of two sediment cores retrieved off the eastern Brazil margin to reconstruct long-term rainfall changes in the hinterland. Our findings from core M125-55-7 (offshore the Doce River, 20°S) reveal that during the past ~320 kyr, precession-paced insolation forcing is the primary pacemaker of variations in SASM precipitation over the Doce basin. We also determined an anomalous interval of weak monsoonal response to insolation forcing during Marine Isotope Stage 6, which we attribute to enhanced wintertime precipitation due to exceptionally strong southeast trade winds created by a steep South Atlantic latitudinal temperature gradient. Moreover, our results suggest that albeit predominantly driven by insolation forcing, the intensity of SASM rainfall responds negatively to GHG forcing, most likely through indirect feedbacks. We propose that GHG forcing directly influences the magnitude of both the inter- and intrahemispheric latitudinal temperature gradients, which in turn modify the strength of atmospheric circulation and precipitation in the tropics. Thus, we suggest that SASM rainfall intensity over tropical eastern Brazil will likely be suppressed by rising CO2 emissions in the future. Our preliminary analysis of core M125-73-3 (off the Contas River; 12°S) reveals regional differences in monsoonal precipitation between the more northerly Contas basin and the more southerly Doce basin. Most notably, unlike the insolation-paced continental rainfall variability recorded at site M125-55-7, SASM rainfall intensity over the Contas basin appears to be more sensitive to glacial-interglacial scale pacing over the past ~800 kyr. Taken together, our records reveal both the high spatial variability in SASM precipitation over eastern Brazil and the dominant influence of orbital forcing on monsoonal rainfall intensity.

29 pages; International audience; A high-resolution stratigraphic analysis of the Upper Cretaceous Gurpi Formation has been undertaken in the Shahneshin section (Zagros Basin, Iran). New results on calcareous nannofossils, planktic foraminifers, dinoflagellate cysts and high-resolution carbon and oxygen stable isotopes form the basis of a reference section for the eastern Tethys that spans the upper Coniacian to the late Danian. Carbon-isotope correlation to Gubbio, Italy and the NW German chalk allows for the identification of many isotopic events as well as for the definition of new events in the Campanian and Maastrichtian. Our results allow for a review of the accurate position of the Coniacian/Santonian, Santonian/Campanian, and Campanian/Maastrichtian stage boundaries relative to carbon isotopes and plankton bioevents. The reliability of Coniacian to Maastrichtian planktic foraminifer, dinoflagellate cysts and calcareous nannofossil biohorizons is assessed.

A high-resolution carbon isotope record is presented for Campanian strata of the Bottaccione section (Umbria-Marche Basin), through an interval that constitutes the standard reference section for the geomagnetic polarity time scale. The identification of prominent δ13C excursions and high frequency variations allows the establishment of robust stratigraphic markers to link this new Tethyan δ13C record with the Boreal realm (Lagerdorf-Kronsmoor section, Northwest Germany and the Trunch borehole, Norfolk, UK). A decoupling of baseline δ13C values between the Boreal and the Tethyan realm is observed during the mid-Campanian, reflecting a plausible change in intermediate/deep-water mass exchange due to a more restricted Tethyan gateway; this is hypothesized to be a consequence of northward movements of Africa associated with opening of the South Atlantic Ocean. Statistical evaluation of a segment of the δ13C dataset with the TimeOpt method for astrochronologic testing provides strong evidence of astronomical forcing, and underscores the potential for development of a complete astronomically tuned Campanian Stage at Bottaccione, allowing astronomical calibration of key geomagnetic and paleobiologic datums.

Changes in Atlantic Meridional Overturning Circulation (AMOC) strength exert a major influence on global atmospheric circulation patterns. However, the pacing and mechanisms of low-latitude responses to high-latitude forcing are insufficiently constrained so far. To elucidate the interaction of atmospheric and oceanic forcing in tropical South America during periods of major AMOC reductions (Heinrich Stadial 1 and the Younger Dryas) we generated a high-resolution foraminiferal multi-proxy record from off the Orinoco River based on Ba/Ca and Mg/Ca ratios, as well as stable isotope measurements. The data clearly indicate a three-phased structure of HS1 based on the reconfiguration of ocean currents in the tropical Atlantic Ocean. The initial phase (HS1a) is characterized by a diminished North Brazil Current, a southward displacement of the ITCZ, and moist conditions dominating northeastern Brazil. During subsequent HS1b, the NBC was even more diminished or yet reversed and the ITCZ shifted to its southernmost position. Hence, dryer conditions prevailed in northern South America, while eastern Brazil experienced maximally wet conditions. During the final stage, HS1c, conditions are similar to HS1a. The YD represents a smaller amplitude version of HS1 with a southward-shifted ITCZ. Our findings imply that the low-latitude continental climate response to high-latitude forcing is mediated by reconfigurations of surface ocean currents in low latitudes. Our new records demonstrate the extreme sensitivity of the terrestrial realm in tropical South America to abrupt perturbations in oceanic circulation during periods of unstable climate conditions.

New palynological and calcareous nannofossil records are presented for the Turonian–Coniacian boundary section at Salzgitter-Salder, Germany, the candidate Coniacian GSSP. The proposed base of the Coniacian Stage is the base of Bed 46, the first appearance datum level of Cremnoceramus deformis erectus, which is coincident with a δ13C minimum at the top of the Navigation carbon isotope event. Palynological assemblages are dominated by organic walled dinoflagellate cysts (dinocysts). Stratigraphic ranges, abundances, species richness, diversity, and assemblage composition data are reported for 137 dinocyst and 119 nannofossil taxa. Dinocyst assemblages are dominated by the peridinioid cyst Palaeohystrichophora infusorioides and the gonyaulacoid cysts of Spiniferites spp. Dinocyst records, events and zonations are assessed. An uppermost Turonian P. infusorioides abundance minimum occurs within the Navigation event, and a marked influx and acme of the taxon with other peridinioid cysts occurs in the lower Coniacian (the P. infusorioides Event). The highest occurrence of Cyclonephelium membraniphorum is recorded at the base of the Coniacian. Correlation of the P. infusorioides Event between Germany, Czech Republic and England is demonstrated. This event represents a productivity pulse, attributed to water-mass reorganisation accompanying early Coniacian eustatic sea-level rise. The nannofossils Biscutum constans, Kamptnerius magnificus and Zeugrhabdotus noeliae, potential cool water indicators, display maximum relative abundances immediately below and above the stage boundary. An increased abundance of Marthasterites furcatus characterises the lowest Coniacian, and a coeval but more extended acme of the species occurs elsewhere. Helicolithus turonicus has its highest occurrence in the lower Coniacian Cremnoceramus walterdorfensis hannovrensis Zone.

Enhanced aridification of Central Asia driven by the combined effects of orogenic surface uplift, Paratethys retreat, changes in atmospheric moisture transport and global cooling is one of the most prominent Cenozoic climate change events of the Northern Hemisphere. Deciphering regional long-term patterns of Central Asian hydrology is, therefore, a key element in understanding the role of Northern Hemisphere mid-latitude drying in the global hydrological system. This study characterizes long-term palaeoenvironmental conditions between the late Oligocene and early Miocene in south-eastern Kazakhstan based on stable isotopes, elemental geochemistry and laser ablation uranium–lead geochronology from alluvial, fluvial and pedogenic deposits. Sedimentary facies and geochemical weathering indices suggest an increased surface and ground water discharge fed by orographically-enhanced precipitation in the Tien Shan hinterland. In contrast, pedogenic stable isotope data and elevated rates of magnesium fixation in clay minerals mirror enhanced rates of evaporation in the vadose zone due to protracted aridification. This study posits that pronounced surface uplift of the Tien Shan Mountains during the Oligocene–Miocene transition promoted regionally increased orographic precipitation and the development of fluvial discharge systems. This article is protected by copyright. All rights reserved.

The δ18O record of well-preserved shells of the inoceramid Inoceramus hercules from the Upohlavy working quarry (Czech Republic) provides an insight into the climate variability in the late Turonian benthic environment of the Bohemian Cretaceous Basin. Similar to modern bivalves, this inoceramid species built its shell near equilibrium with the oxygen isotope value of the ambient water. Due to the nearly year-round shell growth, sequentially sampled δ18O values allowed to estimate the narrowest sub-annual temperatures fluctuations that prevailed during lifetime of the organisms. In accordance with previous studies, reconstructed temperatures suggest colder water conditions (19.0 ± 0.9 °C) during the earliest late Turonian (coinciding with the Hyphantoceras Event; also known as Hitch Wood Event) than during the later part of the substage (20.9 ± 1.1 °C). Climate warming, however, did not affect the sub-annual temperature fluctuations evenly, but predominantly affected the warmest part of the year (at least +4.0 °C). On the contrary, the coldest recorded temperatures remained more or less invariant, varying not (much) more than +1.0 °C across the studied time interval. The observed changes in the benthic temperature estimates likely reflect shifts in seasonal sea surface temperature amplitudes in response to climate forcing. Given the widespread distribution of I. hercules in the upper Turonian–lower Coniacian hemipelagic strata of Europe, the present study sets the basis for future continent-wide sub-annually-resolved climate reconstructions.

During the Late Cretaceous and early Cenozoic the Earth experienced prolonged climatic cooling most likely caused by decreasing volcanic activity and atmospheric CO2 levels. However, the causes and mechanisms of subsequent major global warming culminating in the late Paleocene to Eocene greenhouse climate remain enigmatic. We present deep and intermediate water Nd-isotope records from the North and South Atlantic to decipher the control of the opening Atlantic Ocean on ocean circulation and its linkages to the evolution of global climate. The marked convergence of Nd-isotope signatures 59 million years ago indicates a major intensification of deep-water exchange between the North and South Atlantic, which coincided with the turning point of deep-water temperatures towards early Paleogene warming. We propose that this intensification of Atlantic overturning circulation in concert with increased atmospheric CO2 from continental rifting marked a climatic tipping point contributing to a more efficient distribution of heat over the planet., Ocean circulation likely played a major role in past episodes of global warming. Here the authors show that converging neodymium isotope values indicate intensification of the Atlantic overturning circulation at 59 million years ago, which may have contributed to a more efficient distribution of heat over the planet.

International audience; Earth's climate during the Maastrichtian (latest Cretaceous) was punctuated by brief warming and cooling episodes, accompanied by perturbations of the global carbon cycle. Superimposed on a long-term cooling trend, the middle Maastrichtian is characterized by deep-sea warming and relatively high values of stable carbon-isotope ratios, followed by strong climatic variability towards the end of the Cretaceous. A lack of knowledge on the timing of climatic change inhibits our understanding of underlying causal mechanisms. We present an integrated stratigraphy from Integrated Ocean Drilling Program (IODP) Site U1403, providing an expanded deep ocean record from the North Atlantic (Expedition 342, Newfoundland Margin). Distinct sedimentary cyclicity suggests that orbital forcing played a major role in depositional processes, which is confirmed by statistical analyses of high resolution elemental data obtained by X-ray fluorescence (XRF) core scanning. Astronomical calibration reveals that the investigated interval encompasses seven 405-kyr cycles (Ma(405)1 to Ma(405)7) and spans the 2.8 Myr directly preceding the Cretaceous/Paleocene (K/Pg) boundary. A high-resolution carbon-isotope record from bulk carbonates allows us to identify global trends in the late Maastrichtian carbon cycle. Low-amplitude variations (up to 0.4%) in carbon isotopes at Site U1403 match similar scale variability in records from Tethyan and Pacific open-ocean sites. Comparison between Site U1403 and the hemipelagic restricted basin of the Zumaia section (northern Spain), with its own well-established independent cyclostratigraphic framework, is more complex. Whereas the pre-K/Pg oscillations and the negative values of the Mid-Maastrichtian Event (MME) can be readily discerned in both the Zumaia and U1403 records, patterns diverge during a similar to 1 Myr period in the late Maastrichtian (67.8-66.8 Ma), with Site U1403 more reliably reflecting global carbon cycling. Our new carbon isotope record and cyclostratigraphy offer promise for Site U1403 to serve as a future reference section for high-resolution studies of late Maastrichtian paleoclimatic change.

Deciphering the climatic evolution of the Tibetan Plateau region during the Plio-Pleistocene is hampered by the lack of continuous archives and proxy datasets indicative of moisture availability. Here we assess the suitability of magnetic susceptibility (χ) measured on lacustrine sediments as a paleohydrological proxy based on material from drill core SG-1 (2.69–0.08 Ma) from the western Qaidam Basin. Our assessment is based on directly comparing χ with theArtemisia/Chenopodiaceae (A/C) pollen ratio, which represents a sensitive, well-established proxy for moisture changes in arid environments. We find that higher and lower χ values represent drier and less dry conditions, respectively, for the Late Plio-Pleistocene. Less dry phases were likely caused by transiently increased influence of the westerlies and/or decreased influence of the Asian winter monsoon on glacial–interglacial time scales. An exception from this relationship is the interval between ~ 1.9 and 1.3 Ma, when the SG-1 χ record exhibits a 54 ka cyclicity, which may indicate summer monsoon influence on the Qaidam Basin during that time. After ~ 1.3 Ma, the summer monsoon influence may have ceased due to global cooling, with the consequence that the Asian winter monsoon and the westerlies exerted a stronger control on the hydrology of the Qaidam Basin.

Paleoenvironmental studies and climate models demonstrate that fl uvial runoff and moisture availability in the Caribbean hinterland react very sensitively to climatic variations. Late Pleistocene and Holocene climate records document pronounced dry and wet periods over tropical South America mainly caused by shifts of the Intertropical Convergence Zone (ITCZ). However, forcing mechanisms for changes in the ITCZ position remain controversial. Here we present high-resolution foraminiferal Ba/Ca and δ18Oseawater records from a core located within the Orinoco River outfl ow documenting abrupt hydrological changes in the Orinoco catchment area during the deglacial and Holocene. Our data, obtained from the surface-dwelling foraminifera Globigerinoides ruber (pink), show an abrupt increase in Ba/ Ca ratios in the early Holocene, starting ~600 yr after the end of the Younger Dryas (YD) cold interval at ca. 10.8 ka and suggesting a massive reorganization of moisture sources in northern South America. In contrast, the salinity dependent δ18Oseawater from the same samples shows a gradual decrease starting at the end of the YD. The offset of our Ba/Ca peak excludes meltwater release in conjunction with the northern Andean glacier retreat well before the end of the YD as a forcing mechanism. We suggest that the Ba/Ca record documents an abrupt increase in Ba-rich waters of a northern Andean source caused by the insolation-driven shift of the ITCZ and/or enhanced monsoon activity.

High-resolution osmium (Os) isotope stratigraphy across the Cenomanian–Turonian Boundary Interval from 6 sections for four transcontinental settings has produced a record of seawater chemistry that demonstrates regional variability as a function of terrestrial and hydrothermal inputs, revealing the impact of palaeoenvironmental processes. In every section the 187Os/188Os profiles show a comparable trend; radiogenic values in the lead up to Oceanic Anoxic Event 2 (OAE 2); an abrupt unradiogenic trend at the onset of OAE 2; an unradiogenic interval during the first part of OAE 2; and a return to radiogenic values towards the end of the event, above the Cenomanian–Turonian boundary. The unradiogenic trend in 187Os/188Os is synchronous in all sections. Previous work suggests that activity of the Caribbean LIP (Large Igneous Province) was the source of unradiogenic Os across the OAE 2 and possibly an instigator of anoxia in the oceans. Here we assess this hypothesis and consider the influence of activity from other LIPs; such as the High Arctic LIP.A brief shift to high radiogenic 187Os/188Os values occurred in the Western Interior Seaway before the onset of OAE 2. We evaluate this trend and suggest that a combination of factors collectively played critical roles in the initiation of OAE 2; differential input of nutrients from continental and volcanogenic sources, coupled with efficient palaeocirculation of the global ocean and epeiric seas, enhanced productivity due to higher nutrient availability, which permitted penecontemporaneous transport of continental and LIP-derived nutrients to trans-equatorial basins.

Past river run-off is an important measure for the continental hydrological cycle and the assessment of freshwater input into the ocean. However, paleosalinity reconstructions applying different proxies in parallel often show offsets between the respective methods. Here, we compare the established foraminiferal Ba/Ca and View the MathML source salinity proxies for their capability to record the highly seasonal Orinoco freshwater plume in the eastern Caribbean. For this purpose we obtained a data set comprising Ba/Ca and View the MathML source determined on multiple species of planktonic foraminifera from core tops distributed around the Orinoco River mouth. Our findings indicate that interpretations based on either proxy could lead to different conclusions. In particular, Ba/Ca and View the MathML source diverge in their spatial distribution due to different governing factors. Apparently, the Orinoco freshwater plume is best tracked by Ba/Ca ratios of G. ruber (pink and sensu lato morphotypes), while View the MathML source based on the same species is more related to the local precipitation-evaporation balance overprinting the riverine freshwater contribution. Other shallow dwelling species (G. sacculifer, O. universa) show a muted response to the freshwater discharge, most likely due to their ecological and habitat preferences. Extremely high Ba/Ca ratios recorded by G. ruber are attributed to Ba2+-desorption from suspended matter derived from the Orinoco. Samples taken most proximal to the freshwater source do not show pronounced Ba/Ca or View the MathML source anomalies. Here, the suspension loaded freshwater lid developing during maximum discharge suppresses foraminiferal populations. Both proxies are therefore biased towards dry season conditions at these sites, when surface salinity is only minimally reduced.