Description: Highlights • Complete upper Albian to early Turonian climate archive in drilled core from Tarfaya Basin. • Eccentricity pacing of mid Cretaceous OAE isotope excursions. • MCE and OAE2 associated with climate cooling and sea level fall. Abstract A 325 m long continuous succession of uppermost Albian to lower Turonian pelagic (outer shelf) deposits was recovered from a new drill site in the central part of the Tarfaya Basin (southern Morocco). Natural gamma ray wireline logging, carbonate and organic carbon content, bulk carbonate and organic carbon stable isotopes and X-ray fluorescence (XRF)-scanner derived elemental distribution data in combination with planktonic foraminiferal biostratigraphy indicate complete recovery of the Cenomanian Stage. This exceptional sediment archive allows to identify orbitally driven cyclic sedimentation patterns and to evaluate the pacing of climatic events and regional environmental change across the Albian-Cenomanian boundary (ACB), the mid-Cenomanian Event (MCE) and Oceanic Anoxic Event 2 (OAE2) in the latest Cenomanian. The deposition of organic-rich sediments in the Tarfaya Basin, likely driven by upwelling of nutrient-rich water masses, started during the latest Albian and intensified in two major steps following the MCE and the onset of OAE2. The duration and structure of the MCE and OAE2 carbon isotope excursions exhibit striking similarities, suggesting common driving mechanisms and climate-carbon cycle feedbacks. Both events were also associated with eustatic sea level falls, expressed as prominent sequence boundaries in the Tarfaya Basin. Based on the 405 kyr signal imprinted on the Natural Gamma Ray (NGR) and XRF-scanner derived Log(Zr/Rb) records, we estimate the duration of the Cenomanian Stage to be 4.8 ± 0.2 Myr.

Description: Highlights • Higher lipid content in D. cornigera in Cantabrian Sea than in Menorca Channel. • Lipid composition and δ13C values reflected contrasted food captured by corals. • Feeding on phytoplankton and herbivorous grazers by Cantabrian D. cornigera. • Main trophic role of dinoflagellates and invertebrates for Menorca D. cornigera. • High trophic plasticity of D. cornigera. Abstract The cold-water coral (CWC) Dendrophyllia cornigera is widely distributed in areas of both high and low productivity, suggesting a significant trophic plasticity of this coral depending on the food available in the environment. In this study, lipid biomarkers and their isotopic signature were compared in colonies of D. cornigera and sediment from the highly productive Cantabrian Sea (Northeast Atlantic Ocean) and the less productive Menorca Channel (Western Mediterranean Sea). Lipid content and composition in coral tissue clearly reflected the contrasting productivity in the two areas. Cantabrian corals presented higher content in fatty acids (FA), fatty alcohols and sterols than Menorca corals. Energy storage (saturated + mono-unsaturated FA) to structural (poly-unsaturated FA) ratio was higher in Cantabrian than in Menorca corals. The high ΣC20:1 content as well as PUFA(n-3)/PUFA(n-6) ratio suggest that Cantabrian corals mainly feed on phytoplankton and herbivorous grazers. This is also supported by the higher mono-unsaturated fatty alcohols (MUOH) and long chain mono-unsaturated fatty alcohols (LCMUOH) content in Cantabrian compared to Menorca corals. Conversely, higher PUFA(n-6) content in Menorca corals, with the dominance of C22:4(n-6) and C20:4(n-6), as well as the dominance of cholesterol and norC27Δ5,22 among sterols, point to a higher trophic role of dinoflagellates and invertebrates. The observed geographical variability in trophic ecology supports a high trophic plasticity of D. cornigera, which may favour the wide distribution of this CWC in areas with highly contrasted food availability.

Description: Understanding the controls that determine the spatial distribution and internal heterogeneities of black shales in the Mesozoic ocean has been a focal point of research over many decades. The consensus is that atmosphere–land–ocean interactions influenced variations in marine biogeochemistry and sediment supply, thus exerting fundamental controls on the richness and quality of sedimentary organic matter (OM) and ultimately on petroleum source rock distribution and its generation potential. Internal, small-scale heterogeneities in black shales that have been reported from all ocean settings were often linked to orbitally-driven fluctuations in continental runoff and marine upwelling. The two processes are generically related under the ascending (tropical) and descending (subtropical) limbs of the palaeo-Hadley Cells, with fluctuations at variable time (seasonal, orbital, geological) and spatial (shelf, margin, deep basin) scales. These dynamic variations translate into characteristic patterns of OM quantity and quality, best preserved near the continents where the forcing effects are strongest. The expression of these orbital-scale interactions are not well constrained at the basin scale, however, they may hold a key to better understand the distribution of heterogeneities in black shales. This study presents a conceptual framework that links OM quality and quantity in Cretaceous Atlantic sediments with the dominant processes that operated under the Hadley Cells. Using a comprehensive compilation of bulk organic geochemical data – total organic carbon concentration (TOC), hydrogen index (HI), oxygen index (OI), and kerogen type – we explore how basic geochemical patterns can be used to identify the underlying generic processes. We utilise published and new data from deep ocean sites of the DSDP/ODP program, as well as one palaeo-shelf setting (Tarfaya), spanning a latitudinal transect from the outer subtropics to the palaeo-equator during the Albian, the Cenomanian–Turonian, and the Coniacian–Santonian. This study emphasises the potential of integrating orbital scale datasets and wide spatial coverage as a predictive tool for black shale formation across ocean basins.

Description: As a result of the raising CO2-emissions and the resultant ocean acidification (decreasing pH and carbonate ion concentration), the impact on marine organism that build their skeletons and protective shells with calcium carbonate (e.g., mollusks, sea urchins, coccolithophorids, and stony corals) becomes more and more detrimental. In the last few years, many experiments with tropical reef building corals have shown, that a lowering of the carbonate ion concentration significantly reduces calcification rates and therefore growth (e.g., Gattuso et al. 1999; Langdon et al. 2000, 2003; Marubini et al. 2001, 2002). In the middle of this century, many tropical coral reefs may well erode faster than they can rebuild. Cold-water corals are living in an environment (high geographical latitude, cold and deep waters) already close to a critical carbonate ion concentration below calcium carbonate dissolves. Actual projections indicate that about 70% of the currently known Lophelia reef structures will be in serious danger until the end of the century (Guinotte et al. 2006). Therefore L. pertusa was cultured at GEOMAR to determine its long-term response to ocean acidification. Our work has revealed that – unexpectedly and controversially to the majority of warm-water corals – this species is potentially able to cope with elevated concentrations of CO2. Whereas short-term (1 week) high CO2 exposure resulted in a decline of calcification by 26-29 % for a pH decrease of 0.1 units and net dissolution of calcium carbonate, L. pertusa was capable to acclimate to acidified conditions in long-term (6 months) incubations, leading to slightly enhanced rates of calcification (Form & Riebesell, 2012). But all these studies were carried out in the laboratory under controlled conditions without considering natural variability and ecosystem interactions with the associated fauna. Moreover, only very little is known about the nutrition (food sources and quantity) of cold-water corals in their natural habitat. In a multifactorial laboratory study during BIOACID phase II we could show that food availability is one of the key drivers that promote the capability of these organisms to withstand environmental pressures such as alterations in the carbonate chemistry and temperature (Büscher, Form & Riebesell, in prep.). To take into account the influences of natural fluctuations and interactions (e.g. bioerosion), we aim to merge in-situ results from the two research cruises POS455 and POS473 with laboratory experimental studies for a comprehensive understanding of likely ecosystem responses under past, present and future environmental conditions.

Description: New drill cores from the Lower Aptian historical stratotype at Roquefort-La Bédoule (SE France) provide continuous high-resolution geochemical and isotope records which closely track the onset of OAE 1a in a subtropical intra-shelf basin (South Provençal Basin). The drilling operation recovered a total of 180 m of undisturbed sediments in three holes. The lowermost 67 m correspond to the Bedoulian (core LB1) and are here analyzed in high-resolution using geochemical proxies (stable carbon isotopes, stable oxygen isotopes, and carbonate content) and foraminiferal biostratigraphy. Pervasive bioturbation through core LB1 suggests mostly oxygenated bottom water conditions with transient dysoxic episodes, as shown by higher pyrite and glauconite concentrations within the marlstones. Unprecedented resolution over the negative δ13C excursion preceding OAE 1a (segment C3) reveals a characteristic double trough extending over ∼5.5 m in core LB1. This long-lasting negative excursion was possibly linked to multiple pulses of enhanced CO2 release to the atmosphere. Estimated sedimentation rates of 1.6–2 cm/kyr indicate that the negative δ13C excursion lasted 〉200 kyr, while the main positive carbon isotope shift (segment C4) had a duration of 〉300 kyr. Fluctuations in δ18O suggest transient episodes of climate warming and cooling at the northern margin of the Tethys or even on a more global scale prior to the onset of OAE 1a.

Description: Several new discoveries suggest that the climate of the Cretaceous may have been more different from that of today than has been previously supposed. Detailed maps of climate-sensitive fossils and sediments compiled by Nicolai Chumakov and his colleagues in Russia indicate widespread aridity in the equatorial region during the Early Cretaceous. The very warm ocean temperatures postulated for the Mid-Cretaceous by some authors would likely have resulted in unacceptable heat stress for land plants at those latitudes, however, and may be flawed. Seasonal reversals of the atmospheric pressure systems in the Polar Regions are an oversimplification. However, the seasonal pressure differences between 30° and 60° latitude became quite pronounced, being more than 25 hPa in winter and less than 10 hPa in summer. This resulted in inconstant winds, affecting the development of the gyre-limiting frontal systems that control modern ocean circulation. The idea of Hasegawa et al. (2012) who suggest a drastic reduction in the size of the Hadley cells during the warm Cretaceous greenhouse is supported by several numerical climate simulations. Rapid contraction of the Hadley cell such that its sinking dry air occurs at 15° N latitude rather than 30° N is proposed to occur at a threshold of 1000 ppmv CO2 in the atmosphere. This change will probably be reached in the next century. Keywords

Description: 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.

Description: We present the first full water column Nd isotope (εNd) and concentration data for Caribbean seawater, as well as for stations close to the Orinoco River mouth and in the Florida Straits. The surface inflow into the southeastern Caribbean via the Guyana Current is characterized by an εNdsignature of −10.9, which is a consequence of the mixing of relatively unradiogenic εNdsignatures (−13.6) supplied by the Orinoco River with contributions from the Amazon River (∼−10). Despite the proximity to land, sub-surface and intermediate waters within the Caribbean largely retain the εNdsignatures of their source water masses in the Atlantic. In contrast, the deep waters of the Caribbean show εNdsignatures at least 3 εNdunits more radiogenic than the inflowing Upper North Atlantic Deep Water (UNADW). A εNdshift from −13 to −9.7 can be explained by addition of radiogenic Nd to the deep Caribbean through weathering inputs from land. However, in order to balance such large shifts in εNdwith at the same time modest increases in Nd concentrations, Nd must also be removed from seawater within the basin. It is suggested that the long residence time of deep waters in the Caribbean allows significant interaction of seawater with sinking particles and seafloor sediments resulting in more radiogenic values. These findings have implications for the use of εNdas a proxy for paleocirculation in restricted basins, in which the residence times of the deep waters are long.

Description: We examine ocean changes in response to changes in paleogeography from the Cretaceous to present in an intermediate complexity model and in the fully coupled CCSM3 model. Greenhouse gas concentrations are kept constant to allow a focus on effects arising from changing continental configurations. We find consistent and significant geography-related Cenozoic cooling arising from the opening of Southern Ocean (SO) gateways. Both models show significant deep ocean cooling arising from tectonic evolution alone. Simulations employing continental configurations associated with greenhouse climates, namely the Turonian and the Eocene simulations, systematically exhibit warm deep ocean temperatures at elevated pCO2 close to 10 °C. In contrast, continental configurations associated with (later) icehouse climates are associated with cooler deep ocean temperatures at identical pCO2, arising from a progressive strengthening of the Antarctic Circumpolar Current. This suggests that a component of the Cenozoic benthic cooling trend recorded in oxygen isotopes could arise directly from changes in continental configuration, and so be partially decoupled from the Cenozoic greenhouse gas history. In this paper we will present our model results against the background of an extensive review of previous work on ocean gateways and additional modelling results from several other global climate models.