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The Mochras core, UK, an historic reference site for the study of Early Jurassic calcareous nannofossils, has been reinvestigated here across the Hettangian to Lower Pliensbachian. Both relative and absolute abundances of 24 calcareous nannofossil species reveal patterns and occurrences that define not less than 37 defined biohorizons. However, due to the low abundance of many of those species towards the base and top of their stratigraphical range, we observe large inconsistencies in first and last occurrences of these species. Instead, we consider records of first consistent and last consistent occurrences (FCOs and LCOs), as well as base and top of acme events, as more reliable biohorizons. Accordingly, we assess the reliability of our biohorizons and show that, in addition to previously established zonal and sub-zonal biomarkers, nine non-zonal biohorizons prove to be robust. Based on that, an updated biozonations scheme with additional subzones for NJB has been proposed and tested against other localities. [ABSTRACT FROM AUTHOR]

Cadmium (Cd) isotope signatures (δ114Cd) deduced from modern and ancient marine deposits are often used as a proxy for bioproductivity and for micronutrient cycling, whereas chromium (Cr) isotope signatures (δ53Cr) are used as a potential proxy for oxygenation. The Cretaceous—Paleogene (K/Pg) boundary records one of Earth's five big mass extinctions, which contains geochemical fingerprints of the Chixculub asteroid impact and is coeval with the Deccan Trap volcanism. Here we present for the first time a combined record of Cd and Cr isotopes from the Danish Basin to interrogate the effects on bioproductivity across the K/Pg boundary. The δ114Cd values range between −0.28‰ and 0.27‰ defining an average of 0.05‰ ± 0.24 (2σ, n = 87). Authigenic δ53Cr values range between 0.06‰ and 1.06‰ and define an average of 0.59‰ ± 0.51 (2σ, n = 81). An abrupt jump, across the K/Pg boundary layer, from consistently positively fractionated Cd and Cr isotope signatures recorded in Late Maastrichtian white chalks towards less positively fractionated δ114Cd values and heterogeneous δ53Cr values in the Early Danian carbonates, likely indicates a decrease in surface water bioproductivity. This decrease is accompanied by redox fluctuations in the water column as a consequence of environmental changes either related to the Chixculub impact event and/or to the Deccan volcanic eruptions coeval with this boundary. Assuming an efficient removal of Cd and Cr through consumption and/or adsorption by primary producers, or by incorporation into the skeleton/shells of calcifiers, and using the fractionation factor of Cd into carbonates, we reconstruct surface water conditions during the Late Masstrichtian—Early Danian that are compatible with those of modern oceans, with δ114Cd varying from 0.17 to 0.72‰. Overall, the combined Cr-Cd isotope fluctuations over the K/Pg boundary are consistent with a scenario characterized by climate-induced changes of nutrient availability and concomitant responses of primary production levels, ultimately related to the asteroid impact and to the proceeding volcanic activities that influenced the ocean's chemistry. We anticipate our results to point for further studies of other stratigraphic sections worldwide to reveal an extensive Cd-Cr record for the Cretaceous—Paleogene boundary and its corresponding collapse of bioproductivity and decreasing ocean oxygenation. [Display omitted] • First study of combined Cd and Cr isotopes as tracer applied to carbonates across the Cretaceous—Paleogene boundary. • Coupling of the double tracer Cd-Cr isotopes to bioproductivity in ambient seawater. • Severe changes in Cd and Cr isotopes across the K/Pg boundary linked to the collapse of bioproductivity. • First study to correlate C and O stable isotopes with the non-traditional isotope systems. [ABSTRACT FROM AUTHOR]

We investigate the response of calcareous nannoplankton to the middle-late Eocene transition in the SW Neo-Tethys and compare our data to published results from X-ray diffraction (XRD) analysis, element content from X-ray fluorescence (XRF) and the abundance of microfossils in the coarse fractions of the sediment. The nannofossil assemblage is mainly composed of Reticulofenestra spp. (avg. 44%), Sphenolithus spp. (avg. 20%), Discoaste r spp. (avg. 18%) and Pontosphaera spp. (avg. 10%). The Relative abundance of Zygrhablithus bijugatus and the Chiasmolithus ratio are used with the visual assessment to evaluate the preservation. The Sphenolithus - Reticulofenestra turnover occurred before the MECO at the Lutetian-Bartonian boundary. Besides the significant influence of an evolutionary gradient caused by the disappearance of numerous species of Sphenoliths, Discoasterids, and Coccolithaceae, and the first appearance of multiple species of reticulofenestrids, paleoenvironmental conditions imposed a significant impact on the calcareous nannofossil assemblages. The abundance of ostracods and the planktic/benthic foraminifera ratio depict relative sea-level changes. The microfossil assemblages and the lithological composition of the sediments track paleoclimatic and paleoenvironmental changes across the Lutetian to Priabonian. Dry conditions marked the middle Lutetian, followed by increased variability in hydrolyzing conditions during the late Lutetian and early Bartonian. An eutrophic and restricted ecosystem with high fine-grained material input is suggested for the Priabonian. • Increased calcareous nannofossil diversity from 42 Ma to 38.2 Ma. • An abrupt change from oligotrophic to mesotrophic conditions at ∼42 Ma. • Sphenolithus - Reticulofenestra turnover at the Lutetian-Bartonian boundary. • The nannofossil assemblage expressed no temperature changes. [ABSTRACT FROM AUTHOR]

Earth's future environment depends critically on how the marine ecosystems react to the current greenhouse conditions. Past warming events from the Middle Eocene can shed light on the nature of these reactions. Middle Eocene sedimentary archives from the Tethyan margins record the Middle Eocene Climatic Optimum (MECO) with varying carbon isotope excursions from site to site. The present study integrates stable isotopes, the abundance of benthic fauna, and astrochronology to look for the timing of the MECO peak warming and the maximum abundance of nummulites in the Southern Mediterranean (Tunisia). A mesotrophic environment during the lower Bartonian with high eustatic sea level promotes the formation of a shallow water carbonate platform in central Tunisia from 40.6 Ma to 39.8 Ma. Nummulites occur in low abundance in the Lower Reneiche Limestone unit (LRL, Bey et al., 2015) from 40.6 to 40.2 Ma, then increase, reaching maximum abundance at the Upper Reneiche Limestone unit (URL, 40.1 to 40 Ma). Maximum accumulation of nummulites and negative excursion of δ18O in the URL occurred during the MECO's warming peak (40.07 to 40 Ma), 200 kyr after the middle Eocene third-order maximum flooding surface. The nummulitic beds represent warmer climates and higher sea levels (arid to semi-arid climate), and the short marl intervals reflect enhanced detrital input (humid climate and lower sea level). The eccentricity modulations were extracted using a lowpass filter applied on a wide-band precession filter then we computed the instantaneous amplitude using Hilbert Transform. The Spearman-rank correlation assesses the potential introduction of amplitude modulations during tuning. Power Decomposition Analysis (PDA) indicates a dominant short eccentricity forcing on the regional climate during the MECO with a minor obliquity component. Variations in magnetic susceptibility and CaCO 3 content suggest a combined control of climate and sea-level cycles controlled by eccentricity-modulated precession cycles. • Impact of the MECO on the benthic biota in the southern Mediterranean. • Benthic foraminifera responds to orbital cyclicity for the MECO at 40.2 Ma. • Eccentricity-modulated precession cycles paced climatic variability. • The regional climate is controlled by lower latitude insolation during the MECO. [ABSTRACT FROM AUTHOR]

Late Cretaceous to Early Paleogene time represents a critical transitional period in Earth history. Global events include short-term instability in climate and ocean circulation, large igneous province emplacement, and catastrophic extinction of marine and terrestrial fauna due at least in part to a bolide impact event. The response of the ocean system to Cretaceous-Paleogene (K-Pg) global events has been the subject of much research, yet fundamental questions remain regarding carbon cycling, climate, ocean mixing, and redox conditions. To help elucidate paleoceanographic changes across the K-Pg transition, we revisit the classic Maastrichtian to Danian chalk-limestone succession at Stevns Klint, Denmark with a suite of new geochemical data, including insights from the redox-sensitive chromium isotope system. We use carbon and oxygen isotope trends to form a well-constrained framework for the succession, before presenting strontium isotope, chromium isotope, and rare-earth element data for the units deposited both before and after the K-Pg event. Carbon isotopes show only minor perturbation across the K-Pg boundary and oxygen isotopes record a prominent positive excursion, with both of these trends standing in contrast to many K-Pg boundary sections worldwide. Strontium isotopes record a spike towards more radiogenic values, which is consistent with a globally-observed, short-term weathering pulse. The chromium isotope profile of Maastrichtian chalk begins with strongly positive values followed by a sharp negative excursion associated with a facies shift and initiation of bottom currents in the Chalk Sea. δ 53 Cr values then recover, before falling steadily across the K-Pg boundary and into the Danian limestone. Chromium isotope trends do not correspond to changes in hydrothermal input or basin redox conditions—instead, we propose that mixing of water masses with distinct chromium isotope signatures controlled temporal chromium isotope variability. The local mixing event inferred from our Maastrichtian chromium isotope data could be related to a temporary inflow of Tethyan bottom waters, or the shift from end-Maastrichtian greenhouse warming (associated with Deccan volcanism) to the worldwide cooling phase that immediately preceded the K-Pg boundary. No immediate change in chromium isotopes is recorded across the K-Pg boundary, indicating that the bolide impactor did not substantially perturb the marine chromium cycle, at least at the scale resolvable by our data. Instead, chromium isotope trends continued to be controlled by local oceanographic processes, highlighting the potential of the chromium isotope system to record isotopic heterogeneity and mixing events in ancient oceans. [ABSTRACT FROM AUTHOR]

Detailed facies analysis of a 350 m long core of upper Campanian-Maastrichtian chalk at Stevns Peninsula, eastern Denmark, shows that four mudstone and wackestone chalk facies account for close to 95% of the succession, and that bioturbated mudstone chalk alone accounts for nearly 55% of the sediment. Sedimentation took place in deep water, below the photic zone and storm-wave base, and is characterized by decimetre to metre-scale variations in facies and trace fossil assemblages indicating repeated shifts in depositional environment. Integration of facies with published data on sea-surface temperature and accumulation rates suggests that sea-surface temperature is the most important parameter in controlling stratification of the water column and thereby, indirectly, the observed variations in depositional facies. However, bioturbated mudstone chalk occurs in all stratigraphic levels independent of accumulation rates and sea temperatures and is interpreted to represent a very broad set of deep water environmental conditions with an ample supply of calcareous nannofossil debris and intense bioturbation. Longer term shifts in deposition are best expressed by distribution of clay, flint and bioturbated micro-wackestone, bioturbated wackestone and laminated mudstone chalk facies, whereas the trace fossil assemblages appear less useful. The data set indicates overall shallowing over time with two distinctive events of clay influx to the basin during the late Campanian-earliest Maastrichtian and late Maastrichtian. [ABSTRACT FROM AUTHOR]

Abundance and size changes in the calcareous nannofossil Schizosphaerella are investigated throughout the upper Sinemurian to lowermost Toarcian of the Sancerre-Couy core (Paris Basin). Measurements from 116 samples are compared to 487 and 411 measurements of CaCO 3 content and total organic carbon (TOC) content, respectively. Our results confirm that Schizosphaerella was better adapted to proximal areas than coccoliths as expressed by the stepwise rise in abundance of Schizosphaerella , followed later on by the rise in abundance of coccoliths during the major transgression of the Sinemurian. The new results show that changes in the size of Schizosphaerella were mostly a response to Early Jurassic temperature variations (coldhouse-greenhouse changes). Large average sizes of Schizosphaerella correspond mostly to proximal, cool environmental conditions of the late Sinemurian. Medium average sizes correspond to more distal conditions and cool surface waters whereas small average sizes are associated with warm episodes. These results suggest that the size response of Schizosphaerella to the early Toarcian Oceanic Anoxic Event and to preceding environmental perturbations of the Early Jurassic was probably not a physiological response to lower calcification but rather represent changes in abundances of different ecophenotypes or (sub-)species related to climate change. The contribution of Schizosphaerella carbonate (CaCO 3schizo ) to the total carbonate (bulk CaCO 3 ) in the Paris Basin was minor (< 6%) and short-term fluctuations of both parameters show no correlation. However, the CaCO 3schizo and bulk CaCO 3 show similarities in their long-term trends, suggesting a possible relationship between the biotic carbonate production and the export of allochthonous carbonate to the Paris Basin. [ABSTRACT FROM AUTHOR]

The biostratigraphy of Sinemurian to lower Toarcian calcareous nannofossils has been investigated in the Sancerre-Couy core (Paris Basin), which contains a mixed assemblage of species with affinities to the northern and southern areas of the peri-tethyan realm, thus allowing for the use and calibration of the Mediterranean Province (Italy/S France) and NW Europe (UK) biozonation schemes. This study is based on semi-quantitative analyses of the calcareous nannofossil assemblage performed on 145 samples and the recorded bioevents are calibrated to the NW European Ammonite Zonation and to a new organic carbon isotope curve based on 385 data points. The main bioevents, i.e. the first occurrences of Parhabdolithus liasicus , Crepidolithus pliensbachensis , Crepidolithus crassus , Mitrolithus lenticularis , Similiscutum cruciulus sensu lato, Lotharingius hauffii , Crepidolithus cavus and Lotharingius sigillatus as well as the last occurrence of Parhabdolithus robustus , have been identified. However, we show that a large number of standard biostratigraphic markers show inconsistent occurrences at the base and top of their range, possibly accounting for some of the significant discrepancies observed between the different domains. In addition to the nine main bioevents used for the biozonation of the core, we document an additional 50 distinct bioevents, evaluate their reliability and discuss their potential significance by comparison to previous studies. A total of five significant negative organic carbon isotope excursions are identified and defined in the Paris Basin including the well-documented Sinemurian–Pliensbachian boundary event. One positive excursion is further defined in the Pliensbachian interval. Our calibration of high-resolution calcareous nannofossil biostratigraphy to ammonite biostratigraphy and organic carbon isotopes represents a new stratigraphic reference for the Lower Jurassic series. [ABSTRACT FROM AUTHOR]

We integrate previous Bayesian and astronomically tuned age calibrations of the calcareous nannofossils events with our large-scale correlations to discuss using the standard calcareous nannofossil zonal schemes in the SW Neo-Tethys platform during a period of significant paleoceanographic, tectonic, and paleoclimatic perturbations (middle Eocene to early Oligocene). Two marine on-land sections extend from NP15 (Nanno-Plankton zone) to lower NP23, equivalent to upper CNE9 (Calcareous Nannofossil of the Eocene) to lower CNO3 (Calcareous Nannofossil of the Oligocene), are studied. Calcareous nannofossils have been investigated at less than 96 kyr resolution between 45.55 Ma and 31.9 Ma. The Souar section covers the Top (T) of the Nannotetrina alata group zone (CNE9, Lutetian) to the Isthmolithus recurvus zone (CNE18, Priabonian) in the Pelagic facies of the Tunisian dorsal. The El Rahma section extends from the Helicosphaera compacta zone (CNE21) to the Reticulofenestra umbilicus (CNO2) zone in the Cap Bon peninsula. The distribution patterns were studied through semi-quantitative counts to test the reliability of the biohorizons used in the standard biozonations schemes (Martini, 1971; Agnini et al., 2014). We discuss 14 biohorizons that span 13.65 Myr to highlight the limitations (absence/scarcity) of the Chiasmolithus group, particularly Ch. grandis, Ch. oamaruensis , and Ch. solitus, as biohorizons in the SW Neo-Tethys. Our study shows that Sphenolithus furcatolithoides , Dictyococcites bisectus, Sphenolithus obtusus, and Reticulofenestra erbae are reliable horizons for large-scale correlations with the northern margins of the Neo-Tethys. Calcareous nannofossils from the SW Neo-Tethys margin were highly affected by the paleo-circulation changes due to the episodic restriction of the westward subtropical Eocene Neo-Tethys (STENT) current (Jovane et al., 2009), followed by the closure of the eastern Neo-Tethys. • Calcareous nannofossil biostratigraphy at time resolution below 96 kyr. • Correlation of calcareous nannofossils events between the SW Neo-Tethys and Northern Neo-Tethys (Italy and Turkey). • Reliability of 14 early Paleogene biohorizons between 45.55 Ma to 31.9 Ma. • Sphenolithus furcatolithoides and Sphenolithus obtusus are reliable horizons for correlations with the northern Neo-Tethys. • C hiasmolithus grandis, Ch. oamaruensis , and Ch. solitus are diachronous and inconsistent in the SW Neo-Tethys. [ABSTRACT FROM AUTHOR]

Criticism of the age-model used by Dameron et al. (in press) is commented hereby. This criticism essentially concerns the age of the first occurrence of calcareous nannofossil Micula prinsii at Shatsky Rise, central Pacific, which should not be considered older than 66.6 Ma, rather than 67.3 Ma as considered by the authors. Although this criticism does not fundamentally change the environmental and paleoceanographic interpretations of Dameron et al. (in press), the age of this bioevent influences quite a lot the time scale used for the latest Maastrichtian and thus the actual age of the termination of their main dissolution interval and the duration of the partial recovery in carbonate preservation. We recommend the authors to modify their age-model and to provide alternative durations and ages for the sequence of events in the end-Maastrichtian interval as such revised ages constitute an important base for comparison with the timescale of Deccan volcanism and other end-Cretaceous perturbations. [ABSTRACT FROM AUTHOR]

An integrated study of magnetic mass susceptibility (MS), bulk stable isotopes and calcareous nannofossil paleoecological changes is undertaken on the late Maastrichtian of the Elles section, Tunisia, spanning the last ca. 1 Myr of the Cretaceous. A cyclostratigraphic analysis reveals the presence of Milankovitch frequencies and is used for proposal of two distinct orbital age models and to provide ages of important stratigraphic horizons, relative to the age of the Cretaceous-Paleogene boundary (K-PgB). Principal component analysis (PCA) performed on the nannofossil assemblage reveal two main factors, PCA1, mostly representing fluctuations of D. rotatorius, P. stoveri, Lithraphidites spp., Retecapsa spp., Staurolithites spp., Micula spp., and PCA2, mostly representing fluctuations of A. regularis, C. ehrenbergii, Micula spp., Rhagodiscus spp., W. barnesiae and Zeugrhabdotus spp. Variations in PCA1 and PCA2 match changes in bulk δC and δO, respectively, and suggest changes in surface-water fertility and temperatures and associated stress. The variations in abundances of high-latitude taxa and the warm-water species Micula murus and in bulk δO delineate fast changes in sea-surface paleotemperatures. As in many other sites, an end-Maastrichtian greenhouse warming is highlighted, followed by a short cooling and an additional warm pulse in the last 30 kyr of the Maastrichtian which has rarely been documented so far. Orbital tuning of the delineated climatic events is proposed following the two different age models. Calcareous nannofossil assemblages highlight a decrease in surface-water nutriency, but their species richness remains high through the latest Maastrichtian, indicating, in Tunisia, a weak impact of Deccan volcanism on calcareous nannoplankton diversity before the mass extinction. [ABSTRACT FROM AUTHOR]

New paleoecological data are presented for late Maastrichtian calcareous nannofossil assemblages of the Indian Ocean and the Boreal epicontinental Chalk Sea. These data are compiled with recent results in the tropical Atlantic, Pacific, and Tethys oceans in order to characterize environmental changes by the end of the Cretaceous era. The paleobiogeographic distribution of the warm-water species Micula murus is updated and indicates the existence of major sea-surface currents in the late Maastrichtian Atlantic Ocean similar to the present day. The end-Maastrichtian greenhouse warming is characterized at tropical and subtropical latitudes by an increase in abundance of M. murus and the temporary disappearance of the high-fertility marker Biscutum constans . In the Boreal realm, the greenhouse episode is marked by a contemporaneous acme of Watznaueria barnesiae coincident with very rare occurrences of M. murus and other tropical nannofossil species which have never been reported before at boreal latitudes. A review of cyclostratigraphic and calcareous nannofossil data in the Atlantic, Pacific, Indian, and Tethys oceans points to the following evolution of sea-surface paleotemperatures for the last ca. 350–380 kyr of the Cretaceous: the end-Maastrichtian greenhouse warming lasted on average a little more than 200 kyr and was followed by a ca. 100–120 kyr cooling. In the Tethys, a 30–40 kyr additional pulse of warming is highlighted immediately below the Cretaceous–Paleogene boundary. These findings indicate an important instability of the climate system at the end of the Maastrichtian, most likely caused by Deccan volcanism. The calcareous nannofossil species richness dropped during the end-Maastrichtian greenhouse warming, which may indicate environmental stress and/or ocean acidification. However, nannoplankton diversity returned rapidly to higher values after this climatic episode and remained high up to the Cretaceous–Paleogene boundary. No significant extinction is recorded in this biotic group prior to the boundary clay. [ABSTRACT FROM AUTHOR]

The lithostratigraphy, calcareous nannofossil biostratigraphy, carbon- and oxygen-isotope stratigraphy and gamma-ray profile are presented for the Skælskør-1 core, eastern Denmark. The correlation of carbon isotopes to Gubbio (Italy) and ODP Site 762C (Indian Ocean) provides the chronostratigrahical framework of the core through a tie to magnetostratigraphy. Two new carbon-isotope excursions are defined for the uppermost Maastrichtian of the core and prove useful for long-distance correlation. Twenty stratigraphic tie-points are used for correlation of the upper Campanian-Maastrichtian interval by combining carbon-isotope and gamma-ray variations. Significant dissimilarities in the gamma-ray profiles of the Danish Basin cores preclude the sole use of this tool for basin-scale correlations. Bulk oxygen-isotopes and semi-quantitative abundance changes in the warm-water calcareous nannofossil Watznaueria barnesiae and the cool-water Kamptnerius magnificus highlight the following past changes in sea-surface temperatures ( SSTs): relatively warm late Campanian SSTs, cooling across the Campanian-Maastrichtian boundary and through the early Maastrichtian, warming across the early-late Maastrichtian transition, cooling in the late Maastrichtian, intense warming in the latest Maastrichtian chron C29r, followed by a very short episode of cooling immediately before the Cretaceous-Palaeogene boundary. The late Campanian-Maastrichtian evolution in sea water temperatures inferred from the Danish Basin is similar to that delineated at tropical latitude oceanic sites. [ABSTRACT FROM AUTHOR]

The Toarcian oceanic anoxic event (T-OAE; ∼183 million y ago) is possibly the most extreme episode of widespread ocean oxygen deficiency in the Phanerozoic, coinciding with rapid atmospheric pCO2 increase and significant loss of biodiversity in marine faunas. The event is a unique past tipping point in the Earth system, where rapid and massive release of isotopically light carbon led to a major perturbation in the global carbon cycle as recorded in organic and inorganic C isotope records. Modern marine ecosystems are projected to experience major loss in biodiversity in response to enhanced ocean anoxia driven by anthropogenic release of greenhouse gases. Potential consequences of this anthropogenic forcing can be approximated by studying analog environmental perturbations in the past such as the T-OAE. Here we present to our knowledge the first organic carbon isotope record derived from the organic matrix in the calcite rostra of early Toarcian belemnites. We combine both organic and calcite carbon isotope analyses of individual specimens of these marine predators to obtain a refined reconstruction of the early Toarcian global exogenic carbon cycle perturbation and belemnite paieoecology. The organic carbon isotope data combined with measurements of oxygen isotope values from the same specimens allow for a more robust interpretation of the interplay between the global carbon cycle perturbation, environmental change, and biotic response during the T-OAE. We infer that belemnites adapted to environmental change by shifting their habitat from cold bottom waters to warm surface waters in response to expanded seafloor anoxia. [ABSTRACT FROM AUTHOR]

Cyclostratigraphic analysis of the Maastrichtian limestone–marl alternations of Bidart (SW France) allows the hypothesis of orbital control on lithological cycles to be evaluated. Magnetic susceptibility (MS), oxygen and carbon isotope measurements, sampled at a high resolution, are analyzed using various cyclostratigraphic tools. A statistically significant orbital signal is detected, with a remarkable record of the precession corresponding to the limestone–marl couplets. This well expressed orbital forcing allows the building of a relative cyclostratigraphic time scale for the MS and δ13C records based on the 100kyr eccentricity cycle. The total duration of the section is estimated at 1.44±0.22Myr. Correlation based on calcareous nannofossil biostratigraphy and comparison of the scaled Bidart δ13C record to the astronomically calibrated δ13C signal of ODP Hole 762C shows that the studied section extends from −71.5 to −70Ma, covering the upper part of Chron C32n.1n and 2/3 of Chron C31r. Oxygen isotope data suggest a 2°C cooling of sea-surface temperatures during the studied interval. When placed on the long-term δ18O trend of the Bidart section, this interval is here recognized as the onset of the early Maastrichtian cooling event. With its excellent record of the precessional forcing, the Bidart section, along with other sections of the Basque Country, is a useful tool for the refinement of the Maastrichtian timescale. [ABSTRACT FROM AUTHOR]

Abstract: An integrated framework of magnetostratigraphy, calcareous microfossil bio-events, cyclostratigraphy and δ 13C stratigraphy is established for the upper Campanian–Maastrichtian of ODP Hole 762C (Exmouth Plateau, Northwestern Australian margin). Bulk-carbonate δ 13C events and nannofossil bio-events have been recorded and plotted against magnetostratigraphy, and provided absolute ages using the results of the cyclostratigraphic study and the recent astronomical calibration of the Maastrichtian. Thirteen carbon-isotope events and 40 nannofossil bio-events are recognized and calibrated with cyclostratigraphy, as well as 14 previously published foraminifer events, thus constituting a solid basis for large-scale correlations. Results show that this site is characterized by a nearly continuous sedimentation from the upper Campanian to the K-Pg boundary, except for a 500kyr gap in magnetochron C31n. Correlation of the age-calibrated δ 13C profile of ODP Hole 762C to the δ 13C profile of the Tercis les Bains section, Global Stratotype Section and Point of the Campanian–Maastrichtian boundary (CMB), allowed a precise recognition and dating of this stage boundary at 72.15±0.05Ma. This accounts for a total duration of 6.15±0.05Ma for the Maastrichtian stage. Correlation of the boundary level with northwest Germany shows that the CMB as defined at the GSSP is ~800kyr younger than the CMB as defined by Belemnite zonation in the Boreal realm. ODP Hole 762C is the first section to bear at the same time an excellent recovery of sediments throughout the upper Campanian–Maastrichtian, a precise and well-defined magnetostratigraphy, a high-resolution record of carbon isotope events and calcareous plankton biostratigraphy, and a cyclostratigraphic study tied to the La2010a astronomical solution. This section is thus proposed as an excellent reference for the upper Campanian–Maastrichtian in the Indian Ocean. [Copyright &y& Elsevier]

Abstract: The taxonomy of the calcareous nannofossil Arkhangelskiella is revised using the results of a biometric analysis performed on 599 specimens from various stratigraphic levels throughout the upper Campanian-Maastrichtian of the Stevns-1 borehole, Denmark. Combined qualitative labelling and biometric measurements suggest that this genus comprises at least three distinct morphogroups in this stratigraphic interval, with possibly one additional morphotype. The results show that the descriptions formerly used for the erection of these groups as distinct species do not fit to their observed range in the coccolith length and in the rim width, and that the central opening is an important additional parameter allowing distinction between the different morphogroups. Biometric analysis shows, however, that the morphogroups are strongly overlapping on all measured parameters. Therefore, the three distinct variants of Arkhangelskiella cymbiformis (var. NT, var. N and var. W) formerly described by Varol are reintroduced and emended rather than using distinct species. In addition, a fourth variant is described, A. cymbiformis var. SW. Using observed relationships between the parameters as well as stratigraphic ranges of these groups throughout the latest Cretaceous, evolutionary trends are outlined. [ABSTRACT FROM AUTHOR]

Abstract: The response of calcareous nannofossils to the end-Cretaceous warming is investigated in the Tropical Pacific DSDP Site 577A (Shatsky Rise) through the record of species richness, Shannon diversity, distribution patterns and statistical treatments. This event is marked by a strong acme of the tropical species Micula murus and is accompanied by a decrease of Placozygus spiralis, the disappearance of Biscutum constans and a decrease in bulk δ 13C, indicative of a decrease in primary productivity. An increase in abundance of other Micula species at Site 577A and a drop in species richness recorded in all sites of Shatsky Rise, suggest stressed environmental conditions coincident with the end-Cretaceous warming. The acme of M. murus at Shatsky Rise and in the Atlantic Ocean is recorded within magnetochron C29r and correlates (1) with the intense warming as expressed in intermediate waters through the δ 18O of benthic foraminifera, and in surface waters through poleward migration, reduced diversity and dwarfism in planktonic foraminifer assemblages, (2) with a sharp decline in marine 187Os/188Os, chemical marker of Deccan volcanic activity, and (3) with a rise in the atmospheric pCO2 record of terrestrial plants in Texas, USA, probably triggered by Deccan volcanic degassing. However, a drop of calcareous nannofossil cool-water taxa in the Equatorial and South Atlantic, as well as a first rise in abundance of M. murus in the South Atlantic and Tropical Pacific occur in the topmost part of chron C30n, and correlates with the rise in palaeotemperature record of terrestrial plants in North Dakota, USA. This suggests that initiation of the warming in the atmosphere and surface waters may predate the striking warming of intermediate water masses by 150/200kyr. The coincidence and the links between climate change, volcanism, geochemical and biotic events at the end of the Maastrichtian thus remain to be fully elucidated. [Copyright &y& Elsevier]

Micula murus is one of the main calcareous nannofossil biostratigrapic markers of Tethyan and Intermediate provinces in the upper Maastrichtian (uppermost Cretaceous). A review of its first occurrence at 14 deep-sea sites and sections shows that it is time transgressive from the Tropical Realm of the Atlantic and Pacific Oceans to the intermediate latitudes of the North Atlantic, South Atlantic, Indian Ocean, and the northern Tethys. M. murus remained confined to the Tropical Realm for ∼1.2 m.y. in the early-late Maastrichtian, thus supporting high-latitudinal thermal gradients. It subsequently spread out in the late Maastrichtian to temperate latitudes and to the Tethys in coincidence with the onset of a thermohaline circulation change ca. 67.5 Ma, suggesting a major change in surface-water circulation and interocean communications. [ABSTRACT FROM AUTHOR]

Calcareous nannofossil biostratigraphy and carbon-isotope stratigraphy on bulk organics of the middle-upper Eocene Souar Formation (Tunisia) allow for a refined stratigraphy of this interval in the southwestern Neo-Tethys margin. The Souar Formation represents the deepest sedimentary deposits of the central northern Tunisian Basin and was only dated previously by coarse data on planktonic foraminifera. Together with our new data, a correlation is proposed to previous Tunisian records of the Halk El Menzal carbonate platform to the NE and shallow-water deposits of central Tunisia to the SW, which leads us to the erection of a synthetic stratigraphic chart of the middle-upper Eocene in central and northeastern Tunisia. Our results allow for a review of the accurate position of the Lutetian / Bartonian and the Bartonian / Priabonian stage boundaries in Tunisia relative to calcareous nannofossil biohorizons. We apply Bayesian statistics to build our age-depth model which points to a hiatus in the Lutetian (CNE12 Zone) that we relate to the middle Lutetian regressive sequence leading to the Lu-4 M-cycle. Radiolarian-rich sediments and cherts of the late Lutetian and early Bartonian are interpreted as a response to an increase in productivity, tied to the seasonal upwelling of nutrient-rich waters. Correlation to other sections in Tunisia highlights the strong contrast in facies between the carbonate-rich sequences of the edges of the dorsal and the silica-rich deposition in the Souar Formation. This contrast is particularly pronounced in the interval before and across the Middle Eocene Climatic Optimum (MECO) characterized by a maximum of nummulitic carbonate production on the platform and a minimum of carbonate production in the deep basinal parts of the Tunisian dorsal, rather dominated by silica-rich sediments. • Middle-Late Eocene calcareous nannofossil biostratigraphy in the SW Neo-Tethys. • The MECO corresponds to the Reneiche member in the Tunisian stratigraphic chart. • The MECO is characterized by a δ 13Corg excursion and biosiliceous productivity. • Increase in terrigenous flux to the Tunisian dorsale during the MECO. • Major sedimentation rate variations due to changes in the on-land weathering. [ABSTRACT FROM AUTHOR]

Abstract: The phytoplankton response (calcareous nannofossils) to the Late Maastrichtian climate evolution is investigated in the South Atlantic DSDP Hole 525A and compared to published geochemical and micropaleontological data. The results point to a succession of dramatic climatic fluctuations. “Cool-water indicators” (Ahmuellerella octoradiata, Kamptnerius magnificus and Nephrolithus frequens) suggest cool surface water conditions prevailed during Chron C30n. At the top of C30n, their sudden drop in abundance, the last occurrence of B. constans and the concomitant increase in the tropical species Micula murus suggest warming and lower surface water productivity. An M. murus acme within Chron C29r reflects maximum warming. During the last 100 kyr of the Maastrichtian, the decrease in M. murus and increase in cool-water indicators reflect rapid cooling with the cool climate persisting over. The calcareous nannoplankton response to climate change correlate with similar findings in the Equatorial Atlantic Hole 1258A and parallels the stable isotope record of planktic and benthic foraminifera of DSDP Hole 525A as well as the decline in 187Os/188Os. Comparison of this marine record and the continental climate record in North America suggests a link between Deccan volcanism and the late Maastrichtian warm event. [Copyright &y& Elsevier]

This paper is devoted to the following incremental problem. Initially, a graph and a distinguished subset of vertices, called initial group, are given. This group is connected by an initial tree. The incremental part of the input is given by an on-line sequence of vertices of the graph, not yet in the current group, revealed on-line one after one. The goal is to connect each new member to the current tree, while satisfying a quality constraint: the average distance between members in each constructed tree must be kept in a given range compared to the best possible one. Under this quality constraint, our objectives are to minimize the number of critical stages and the number of elementary changes of the sequence of constructed trees. We call "critical" a stage where the inclusion of a new member implies heavy changes in the current tree. Otherwise, the new member is just added by connecting it with a (well chosen) path to the current tree. In both cases, updating a tree implies a certain number of elementary changes (that we define). We propose a strategy leading to at most O(log i) critical stages (i is the number of new members) and to at most a constant average number of elementary changes per stage. We also prove that there exists situations where Ω(log i) critical stages are necessary to any algorithm to maintain the quality constraint. Our strategy is then worst case optimal in order of magnitude for the number of critical stages criterion and induces a constant number of elementary changes in average per stage. [ABSTRACT FROM AUTHOR]

The Early Jurassic nannofossil Schizosphaerella has displayed major changes in its mean valve size through time. These variations are investigated in detail in the Sinemurian to lowermost Toarcian of the Sancerre-Couy core (Paris Basin), based on previously published measurements of 7050 specimens. Through multivariate morphon analysis and mixture analysis, we decipher three distinct overlapping varieties of Schizosphaerella (small, medium, large) and show that mean size changes of this taxon can be mostly related to variations in the relative abundance of these three varieties. Comparison to facies changes and to newly and previously acquired geochemical data (bulk carbonate C and O isotopes and organic C isotopes, %CaCO 3 and TOC) suggest that, whilst sea-surface temperature was indeed an important driver of size changes in Schizosphaerella , it is insufficient on its own to explain the full variability of our dataset. Likewise, sea-level controlled proximal-distal variations and levels of nutrient supply were additional drivers of Schizosphaerella size changes. The small population of Schizosphaerella remains, however, a good indicator for warmer episodes. [Display omitted] • Schizosphaerella is composed of three pseudo-cryptic variants • The 3 variants strongly overlap and are only distinguishable by biometric studies • Sea-level and temperature are main drivers of Schizosphaerella size changes • Bulk δ18O matching global trends limited to late Pliensbachian [ABSTRACT FROM AUTHOR]

The Lower Cretaceous Tuxen (lower Hauterivian - upper Barremian) and Sola (upper Barremian - Albian) Formations in the Danish Central Graben (North Sea) constitute one of the oldest chalk successions recorded globally, but have received little attention with regards to sedimentary facies and depositional processes. This study presents the first comprehensive carbonate facies analysis of the succession, retrieved from seven drill cores from the Valdemar and Adda Fields. A total of 50 facies are identified, based on a continuum of six lithologies ranging from chalk to marlstone and tuffaceous siltstone to sandstone that display eight different sedimentary structures or fabrics, and two redox-associated lithological color variations (green and red) in the Adda Field. The eight sedimentary structures record: (i) comprehensive bioturbation of homogeneous sediment during fully oxygenated benthic conditions and low sedimentation rates; (ii) a similar bioturbation process but in heterogeneous sediment with lithological contrasts permitting visible burrows to form, perhaps due to rhythmic alternation between pelagic (clay-poor) and hemipelagic (clay-rich) sedimentation; (iii) pelagic to hemipelagic suspension settling in dysoxic to anoxic bottom-water conditions; (iv) patchy cementation of the shallow sea bed during incipient hardground formation; (v) reworking of bioclasts and chalk intraclasts by bottom or wave-induced currents and cohesive debris flows; (vi) pressure solution during late burial diagenesis; (vii) shear deformation by intense plastic deformation of unlithified sediment from limited lateral displacement; and (viii) silicification during burial diagenesis. The facies distribution indicates that active tectonism took place prior to the onset of anoxia that resulted in deposition of the Munk Marl Bed, which in the Valdemar Field was followed by tectonic waning and repeated anoxia. The Valdemar Field constituted a basinal depocenter and was flanked to the east by an early inversion high in the Adda Field characterized by condensation and bypass. The Fischschiefer Member represents a return to prevailing anoxia, consistent with global records of the early Aptian Oceanic Anoxic Event 1a (OAE-1a). [ABSTRACT FROM AUTHOR]

The Rhaetian (~201–209 Ma, the latest stage of the Triassic) is an important time-interval for the study of environmental changes preceding the End-Triassic Mass extinction. A detailed sedimentological and chemostratigraphic study was conducted in the lower Kössen Formation at Hochalm (Austria), the type-section of the Hochalm Member (Mb). This section exposes mid-Rhaetian sediments deposited in an intraplatform shallow marine basin on the north-western margin of the Tethys. The study highlights eight apparent shallowing-upward sequences from the middle of Unit 2 to Unit 4 of the Hochalm Mb stacked within the long-term transgression that characterizes the Kössen Formation. Both the bulk carbonate and the bulk organic matter δ13C records indicate the presence of a distinct increase in carbon isotope values in the lower part of the lower Hochalm Mb. This excursion might represent a new chemostratigraphic marker that could be used for refining the Rhaetian stratigraphy and represents another important Late Triassic carbon-cycle perturbation prior to the major disturbance associated with the End Triassic biotic crisis. • Detailed paleoenvironmental model of the Hochalm Mb. • Shallowing-deepening sequences related to sea-level changes. • Carbon isotope stratigraphy in mid-Rhaetian Hochalm Mb. • Distinct increase in carbon isotopes in the lower Hochalm Mb. [ABSTRACT FROM AUTHOR]

Coniacian to Maastrichtian changes in calcareous nannofossil assemblages have been investigated in the eastern Tethyan Shahneshin section (central Zagros Basin, Iran). The nannofossil assemblages are mainly composed of Watznaueria spp. (avg. 54%), Retecapsa spp (avg. 7.9%), Cribrosphaerella ehrenbergii (avg. 7.7%) and Micula spp. (avg. 5.7%). Throughout the late Campanian, there is a trend to lower abundances in Watznaueria spp. together with increasing abundances of C. ehrenbergii and Arkhangelskiella cymbiformis , which are considered in this basin as the main cool-water taxa. Our results reveal that, despite a diagenetic impact on calcareous nannoflora, a number of primary paleoecological trends are preserved which depict well features of the progressive Late Cretaceous cooling. The first pronounced cooling episode occurs across the late Campanian to early Maastrichtian. The onset of pronounced cooling in the eastern Tethys appears to occur prior to the Campanian/Maastrichtian Boundary event (CMBE) δ13C negative excursion, in contrast with the Boreal realm where pronounced cooling only occurs in the early Maastrichtian, postdating the onset of the CMBE. The coincidence of this earlier cooling in the Zagros Basin with an interval characterized by a significant increase in benthic foraminifera suggests an amplified response of the assemblage due to a change to shallower environments. Hence, the late Campanian calcareous nannofossil assemblage turnover in central Zagros is either a response to an early cooling trend in the eastern Tethys or to sea-level fall or both. The mid-Maastrichtian warming and late Maastrichtian cooling episodes are also delineated in the nannofossil assemblage of Shahneshin and likely correlate with similar episodes in the Boreal Realm. • The first quantitative study on the Late Cretaceous calcareous nannofossil assemblages from the Eastern Tethys (Zagros). • The first palaeoecological record of the Late Cretaceous cooling in the eastern Tethyan Realm (Zagros). • Cribrosphaerella ehrenbergii and Arkhangelskiella spp. are considered as the best cool-water indicators in the Zagros Basin in this study. • The late Campanian–early Maastrichtian cooling appears to occur earlier in eastern Tethys compared to the Boreal Realm. [ABSTRACT FROM AUTHOR]

A high-resolution study of carbon isotope stratigraphy and calcareous nannofossil biostratigraphy has been undertaken on the Upper Cretaceous sediments of the Gurpi Formation (Fm.) in the Bowan section (Zagros Basin, Iran). The integrated stratigraphy of the section allows for large-scale correlation with Upper Cretaceous reference sections (Gubbio, Italy; German Chalk; Shahneshin, Iran) and suggests the age of the Gurpi Fm. at Bowan to be latest Santonian to early Selandian. Correlation of the isotopic data from Bowan to the Shahneshin section in the central Zagros mountains shows remarkable similarity that may be related to effects specific to the peculiar stratigraphy of the area and, possibly, to the long-term evolution of seawater δ13C in the Zagros Basin. A sequence stratigraphic framework is proposed for both sections. Correlation of the two sections to data from the Boreal realm, Indian Ocean, equatorial Pacific Ocean, and other Tethyan sections suggests that it is possible to identify some of the previously defined major carbon isotope events in the Iranian sections. Significant differences, however, are observed in absolute values and overall amplitude of carbon isotope trends. In particular, our results show that the Santonian/Campanian boundary event (SCBE) which is a well-defined, double-peaked, positive excursion at Gubbio and in the Boreal realm is absent in the Zagros Basin, eroded by a major sequence boundary. Moreover, the most pronounced feature in Upper Cretaceous carbon isotope ratios of the Zagros Basin carbonates is an overarching maximum culminating in the early Campanian which correlates with a discrete, low-amplitude (0.25‰) positive excursion defined as the papillosa Zone event at Gubbio and in the Boreal realm. Our results thus reveal a contrasting evolution of carbonate δ13C during the early Campanian between different oceanic basins but also within the Tethys. • The Upper Cretaceous bio- and isotopic data of central Zagros reveals the long-term evolution of seawater δ13C. • The most prominent feature in δ13C trend of Zagros appears to be the significant increase in the papillosa Zone event. • Two significant hiatuses at the uppermost Campanian–early Maastrichtian and latest Maastrichtian–early Danian are identified. • The two identified significant hiatuses in the Zagros Basin are linked here to tectonic uplifts. • The Santonian/Campanian boundary event (SCBE) is poorly expressed in the Zagros Basin. [ABSTRACT FROM AUTHOR]

The late Campanian – Maastrichtian (~74–66 Ma) was characterized by a long-term cooling trend that marks a transition from extreme greenhouse conditions associated with the mid-Cretaceous to cooler conditions that precede the Cenozoic climate. Sparse availability of stable isotope data and the low temporal resolution of biozonations hinder our understanding of this interval, especially for open ocean records. Provincialism of calcareous planktonic taxa also occurred during this time, making it difficult to develop a global biostratigraphic scheme. Calcareous nannofossils are sensitive indicators of surface water, making this fossil group a useful proxy for understanding Late Cretaceous climatic events and correlating these events across different ocean basins. This study expands on the work of Thibault and Gardin (2007), that explored the paleoclimatic evolution of late Maastrichtian calcareous nannofossils from Deep Sea Drilling Project (DSDP) Hole 525A in the South Atlantic. The completeness of its late Campanian – Maastrichtian record makes Hole 525A an ideal site for this study. Furthermore, high-resolution stable isotope datasets have been published, making this section useful for correlation to other ocean basins. A total of 72 smear slides from DSDP Hole 525A, spanning approximately 74–66 Ma, were analyzed. Absolute abundances were determined by counting approximately 300 specimens and two additional traverses were scanned for rare species. Given that this is a low middle latitude site, the calcareous nannofossil assemblage is predominantly comprised of cosmopolitan species, with little evidence of provincialism. This means that sea surface temperature changes are not as well expressed at this site. Despite the dominance of cosmopolitan species, abundance increases of "Cool-water indicators" (Ahmuellerella octoradiata, Kamptnerius magnificus and Nephrolithus frequens) are still observed in this section.In addition to the evidence presented for cool surface water conditions prevailing during the late Maastrichtian (Chron C30N) (Thibault and Gardin, 2007), increases in "Cool-water indicators" are also observed at the base of the early Maastrichtian (Chron C32n1r through the middle of Chron C31r) and two peaks during the late early Maastrichtian (uppermost Chron C31r). These fluxes of "Cool-water indicators" further support onset of global cooling during the late Campanian – early Maastrichtian, evidenced by a rapid, positive oxygen benthic foraminiferal isotope excursion recorded at numerous deep ocean sites. Traditionally viewed as a low-fertility indicator, the gradual decrease in abundance of Watznaueria barnesiae is observed throughout the section, seemingly following the gradual global cooling trend. Fluctuations in abundance are superimposed on this general decrease. The highest abundances precede the Campanian/Maastrichtian boundary. Increases in abundance also occur throughout the middle Maastrichtian (Chron 31n through Chron 30r), possibly coinciding with the collapse of rudist bivalve-dominated reef systems and the extinction of inoceramid bivalves during the Mid-Maastrichtian event. ReferencesThibault, N., & Gardin, S. (2007). The late Maastrichtian nannofossil record of climate change in the South Atlantic DSDP Hole 525A. Marine Micropaleontology, 65(3), 163-184. [ABSTRACT FROM AUTHOR]

The Middle Ordovician outer shelf section of Steinsodden (Norway) shows exquisite marl-limestone alternations with subtle variations in thickness. The section is very well-dated by conodonts allowing correlation to the Baltoscandian conodont and graptolite zonations, and spans the Dapingian to Darriwilian stages. Here, we demonstrate an unambiguous orbital origin of the alternations, allowing for an astronomical calibration of this important time interval that spans the main radiation phase of the Great Ordovician Biodiversification Event (GOBE). A shift in carbonate sedimentation from precession-dominated in the Dapingian and lower Darriwilian to 405 kyr eccentricity-dominated in the middle Darriwilian is in direct coincidence with an increase in the diversity of Baltoscandian conodonts. The conodont diversification correlates with a similar increase in the diversity of Baltoscandian brachiopods, which in turn, have been shown to coincide with a +1‰ increase in benthic oxygen isotopes. The amplitude of isotopic change and its coincidence to the major switch in the dominance of orbital components reflect a scenario that bears similarities to that of the Eocene/Oligocene boundary transition, suggesting that glaciation could have triggered the main radiation phase of the GOBE. [ABSTRACT FROM AUTHOR]

Drilled in 1983, DSDP Site 534A is a prime location to investigate marl-limestone alterations from the middle Tithonian to the earliest Barremian. In 336 metres, the studied interval encompasses a nearly complete succession, allowing a high-resolution long-term study for this critical interval of Earth's history. To strengthen the Stratigraphy of the Jurassic-Cretaceous system boundary, we integrate the already published magnetostratigraphic, chemostratigraphic (bulk carbonate carbon isotopes) and biostratigraphic framework of the core (based on nannofossils, radiolarians, dinoflagellates and calpionellids) with cyclostratigraphy based on high-resolution (4cm) XRF data. Astronomical tuning of the core suggests a total duration of ~19 million years for the studied interval. Interestingly, long-term trends in the Ca/Fe ratio compare well with that of carbon isotopes. These trends are forced by the 9.1 Myr grand eccentricity cycle, placing the Weissert event close to a maximum of this grand cycle. Astronomical configuration appears to have played a major role in the development of this oceanic anoxic event. [ABSTRACT FROM AUTHOR]

In the Northern Calcareous Alps of Austria, Tethyan marls, clays and limestones of the upper Zlambach facies outcrop in excellent conditions in the Roßmoosgraben section (east of Bad Goisern, Oberösterreich). These sediments were deposited in a toe-of-slope to basinal paleoenvironment and thus constitute a rare example of Rhaetian open ocean conditions of the northern Tethys. Calcareous nannofossils are abundant in these sediments and their preservation is generally moderate, allowing for assessing potential changes in assemblages. Absolute and relative abundances of nannofossils and changes in the size of Prinsiosphaera triassica have been established for 65 samples across the V. stuerzenbaumi to C. marshi ammonite zones and compared to high-resolution bulk carbonate carbon isotopes. Two large 1.5 per mil negative excursions in carbon isotopes are recorded in the C. marshi zone and are accompanied by significantly lower total abundance in calcareous nannofossils but no significant change in the composition of the assemblage. Organic-rich black shales prevail in the uppermost 3 m of the Roßmoosgraben section and contain an unusually high abundance of the nannolith Tetralithus and significantly smaller specimens of Prinsiosphaera triassica. In addition, the total number of coccoliths, which represent the earliest representatives of coccolithophorids, is higher in this interval. These results suggest that a possible change in fertility conditions of surface waters favoured the thriving of the primitive coccolithophorids and accompanied bottom water anoxia. Our study shows that even though Rhaetian calcareous nannofossil assemblages have a low diversity, changes in their composition and in their size can be used to depict significant environmental changes. Also, the Rhaetian was characterized by unstable environmental conditions as attested by rapid shifts in the carbon cycle and episodes of ocean anoxia. [ABSTRACT FROM AUTHOR]

An atlante is a corbel figure (or pillar support) sculpted in the form of a man carrying a heavy load. A group of well-preserved stone carved atlantes from c. 1250 carrying the vaults of the Ribe Cathedral in western Jylland, Denmark, represents the antique titan Atlas and are up to 150 cm high. Their obviously foreign origin has so far remained uncertain. The figures are made of a relatively soft, sandy limestone. A new nannofossil analysis of small chips of the chalky and sandy limestone narrows the age of the stone down to the late Campanian (Late Cretaceous). Upper Campanian sandy limestones of this type are exposed in the Münster Basin in North Rhine-Westphalia, western Germany. The Campanian Baumberger Sandstein in this region fits well with the atlantes in terms of lithology and age and is the only possible provenance of the stone. Around 1250 the Baumberger Sandstein was used for baptismal fonts as far north as Ostfriesland at the Dutch-German border, and it is a novel finding of this investigation that it even reached Denmark. The stone was most likely floated along the rivers Lippe and Rhine and shipped via the Wadden Sea to Ribe. It is a remarkably long transport distance for historic commercial stone transportation in continental northern European art in the High Middle Ages. [ABSTRACT FROM AUTHOR]

The organic matter content of marine sediments is often used to infer past changes in ocean conditions. However, the organic carbon pool preserved in coastal sediments is a complex mixture derived from different sources and may not reflect in situ processes. In this study, we combine taxonomic identification of reworked palynomorphs with pyrolysis organic geochemistry and reflected‐light organic petrographic microscopy to investigate the provenance, composition and preservation of organic matter in a marine sediment core retrieved from the NE Greenland shelf. Our study reveals continuous yet variable input of land‐derived organic carbon to the marine environment throughout the late Younger Dryas–Holocene, with the highest input of inert carbon in the late Younger Dryas. Although the sediments contain some recent marine palynomorphs, there is no other evidence of fresh marine organic carbon. In contrast, our results indicate that these shelf sediments represent a significant sink of recycled organic carbon. The results of pyrolysis geochemistry revealed that ~90% of the total organic carbon in the sediments is inert. The organic petrography analyses revealed that >70–84% of the organic carbon in the sediment core is terrigenous. Reworked dinoflagellate cysts showed a continuous provenance of Cretaceous land‐derived material, most likely from the nearby Clavering Island. Our study points to the importance of constraining the organic matter origin, composition and preservation in marine sediments to achieve more accurate palaeoenvironmental reconstructions based on organic proxies. [ABSTRACT FROM AUTHOR]

Abstract Middle to late Rhaetian toe–of–slope to basin deposits (Zlambach Formation) of the Northern Calcareous Alps in the Tethyan realm have been studied with respect to depositional palaeoenvironments and chemo- and sequence stratigraphy, using high-resolution stable isotope and X-ray fluorescence measurements, microfacies and microfossil analysis. Our results show that the Zlambach Formation represents a regressive-transgressive succession which includes one 3rd order and two 4th order depositional sequences as well as several subordinate sedimentary cycles reflecting variations of calciturbidite input from the Dachstein platform due to minor sea-level fluctuations. We present the first high-resolution δ13C carb record for the Middle and Upper Rhaetian interval of the west Tethyan open marine realm. The data show, in contrast to earlier suggestions, that growth and progradation of the Dachstein carbonate platform margin was continuous until the early Choristoceras marshi ammonoid zone (upper Rhaetian). In the late C. marshi zone the Hallstatt basin was affected by significant environmental perturbations as recorded by a 1.0‰ C carb negative excursion followed by a 1.3‰ positive excursion and contemporaneous fluctuations in benthic microfossil abundance and diversity. The occurrence of comparable carbon isotope excursions in the late C. marshi zone of intraplatform basinal deposits of the Northern Calcareous Alps suggests that these perturbations were of a higher significance than previously thought. These isotope excursions could be related to regional ecologic changes such as the late Rhaetian termination of the Dachstein platform margin growth. [ABSTRACT FROM AUTHOR]

A high-precision global time scale for the Early Jurassic is important for understanding the relationship between biotic, climatic and sea-level changes that occurred during this time interval. In this study, we present a cyclostratigraphic analysis of iron (Fe) and titanium (Ti) elemental data from the Pliensbachian marine mudstone succession of the Sancerre-Couy drill core (Paris Basin, France). Time-series analysis of the data, coupled with existing broad chronological constraints, reveals 405 kyr long-eccentricity, 133–100 kyr short-eccentricity, and 34 kyr obliquity cycles in Ti and Fe abundance. Based on astronomical tuning of the 405 kyr long eccentricity cycles, we construct an astrochronology for the Pliensbachian Stage in the Sancerre-Couy record spanning ∼7.9 Myr. Anchored in numerical time, our new Pliensbachian timescale can be correlated with the thicker, likely more complete, astronomically calibrated Pliensbachian record in the Mochras Farm (Llanbedr) borehole. This exercise suggests the presence of significant hiatuses near the base and top of the Sancerre-Couy record. The recently developed sedimentary noise model for inferring sea-level change has also been applied and compared to previous estimates of Pliensbachian sea-level change derived from the Sancerre-Couy record and elsewhere. Analysis of the sedimentary noise modeling results, previously published nannofossil abundance data and our elemental data suggests the presence of million-year scale cycles linked to long-period astronomical forcing. This work provides new constraints on the chronology of the Pliensbachian and its constituent faunal zones, and the role of long-period astronomical forcing in mediating Early Jurassic paleoclimate and sea-level. • The Pliensbachian Stage spanned ∼7.9 Myr. • The timing and duration of Pliensbachian ammonite zones and subzones are constrained. • Sedimentary noise modeling provides new details on relative sea-level changes. • Long astronomical forcing had an impact on paleoclimate and sea-level variations. [ABSTRACT FROM AUTHOR]

Ikaite and pseudomorphs thereafter ("glendonites") are a potentially powerful tool for palaeoclimatic studies, as a low-temperature proxy. However, much uncertainty still surrounds the drivers of ikaite formation, in particular prerequisite thermal and chemical conditions. Furthermore, the ikaite to glendonite transformation is not fully understood, and it was unclear which calcite phases in glendonites were ikaite-derived and which were later diagenetic calcites. This leads to difficulties in choosing which phase to analyse in order to reconstruct the original ikaite growth environmental conditions. Petrographic examination of air-transformed ikaite from the Isatkoak Lagoon in Utqiaġvik, Alaska, confirms that both 'Type I' and 'Type II' calcite phases seen in glendonites are directly derived from ikaite breakdown and not from secondary sources. Clumped isotope temperature reconstructions for transformed ikaites from Utqiaġvik, and comparison to Recent glendonites from the White Sea, Russia, confirm that clumped isotope thermometry may be used to reconstruct ikaite growth temperatures, whilst stable isotopes and minor elemental analysis reveal that a range of geochemical conditions characterise ikaite growth sites. [ABSTRACT FROM AUTHOR]

Cylindrical borings assigned to ichnospecies Trypanites mobilis Neumann, Wisshak & Bromley, 2008, are common in bulbous echinoid spines (Tylocidaris baltica and Ty. vexilifera) and globular calcareous sponges (Porosphaera globularis) from the Maastrichtian chalk and Danian limestone of eastern Denmark. Trypanites mobilis was originally described as being restricted to these substrates but is here reported also from crinoid fragments and asteroid ossicles. A revised diagnosis of Tr. mobilis is proposed to accommodate the broader spectrum of host bioclasts and the fact that some bioclasts, notably Porosphaera, are fully penetrated. Trypanites mobilis is interpreted as a mobile shelter for sipunculan worms and the first appearance of this trace fossil around the Early/Late Cretaceous transition is inferred to reflect intensified predation pressure, and a general shortage of hard substrates on the muddy chalk sea floor. Trypanites mobilis is very common in the Maastrichtian of Denmark. It then nearly disappears in the lower Danian, re-occurs in the middle Danian, at first with smaller sizes and in low numbers, before becoming numerous and large-sized again around the middle/upper Danian transition. The near absence of Tr. mobilis in the lower Danian and its low abundance in the middle Danian is suggested to reflect that the ‘substrate makers’ were affected by ecological instability following the Cretaceous–Palaeogene mass extinction. Trypanites mobilis disappeared after the mid/late Danian transition, i.e. before extinction of its Danian substrate-maker Ty. vexilifera. [ABSTRACT FROM AUTHOR]

Marine sedimentary ikaite is the parent mineral to glendonite, stellate pseudomorphs found throughout the geological record which are most usually composed of calcite. Ikaite is known to be metastable at earth surface temperatures and pressures, readily breaking down to more stable carbonate polymorphs when exposed to warm (ambient) conditions. Yet the process of transformation of ikaite to calcite is not well understood, and there is an ongoing debate as to the palaeoclimatic significance of glendonites in the geological record. This study uses a combination of techniques to examine the breakdown of ikaite to calcite, outside of the ikaite growth medium, and to assess the palaeoclimatic and palaeoenvironmental significance of stable and clumped isotope compositions of ikaite-derived calcite. Powder X-ray diffraction shows that ikaite undergoes a quasi- solid-state transformation to calcite during heating of samples in air, yet when ikaite transforms under a high temperature differential, minor dissolution-recrystallisation may also occur with the ikaite structural waters. No significant isotopic equilibration to transformation temperature is observed in the resulting calcite. Therefore, in cases of transformation of ikaite in air, clumped and stable isotope thermometry can be used to reconstruct ikaite growth temperatures. In the case of ancient glendonites, where transformation of the ikaite occurred in contact with the interstitial waters of the host sediments over unknown timescales, it is uncertain whether the reconstructed clumped isotope temperatures reflect ikaite crystallisation or its transformation temperatures. Yet clumped and stable isotope thermometry may still be used conservatively to estimate an upper limit for bottom water temperatures. Furthermore, stable isotope along with element/Ca ratios shed light on the chemical environment of ikaite growth. Our data indicate that a range of (bio)geochemical processes may act to promote ikaite formation at different marine sedimentary sites, including bacterial sulphate reduction and anaerobic oxidation of methane. The colours of the ikaites, from light brown to dark brown, indicate a high organic matter content, favouring high rates of bacterial sulphate reduction as the main driver of ikaite precipitation. Highest Mg/Ca ratios are found in the most unstable ikaites, indicating that Mg acts to destabilise ikaite structure. [ABSTRACT FROM AUTHOR]

The middle Miocene Kareem Formation is a major hydrocarbon reservoir in the Gulf of Suez rift basin. The middle Miocene Kareem Formation is a major hydrocarbon reservoir in the Gulf of Suez rift basin. The age of this formation has remained controversial due to the lack of clear marker species and the presence of barren intervals in evaporite seals or sand reservoirs. Furthermore, until now, the absolute age and duration of a well-known recognized hiatus (T40) in this formation has not been estimated. Here, we establish the precise age and extent of the Kareem Formation based on the integration of foraminifer and calcareous nannofossil biostratigraphy, with the establishment of an astronomically tuned timescale (ATS) based on gamma-ray variations of two wells, Gs197-2 in the October Basin and J58-81 in the July Basin. These two wells represent the most complete cored sequence of the Middle Miocene Kareem Formation, recording six calcareous nannofossil, four planktonic, and one benthic foraminiferal biohorizons, that enable us to define the Langhian-Serravalian boundary. According to our new biostratigraphically-supported ATS, we estimate that the Kareem Formation spans from 13.25 to 15 Ma. The T40 hiatus is identified in both wells at the boundary between the Shagar and Rahmi Members, with an estimated duration of ca. 0.26 Myr and 0.18 Myr for Gs197-2 and J58-81, respectively. A pronounced obliquity imprint is recorded in the upper Langhian to Serravalian of Gs197-2 well, right above the T40 hiatus. • Astronomical tuning combined with Miocene calcareous nannofossils and plankton foraminiferal biozones. • The Kareem Formation spans 13.25 to 15.15 Ma in the Gulf of Suez, Egypt. • A major T40 hiatus is found within the Kareem Formation at the Langhian-Serravalian boundary. [ABSTRACT FROM AUTHOR]

Macrofossil calcite plays a central role for palaeoenvironmental reconstructions because its preservation state and geochemical signatures can be checked using a variety of screening techniques. Reconstructions of the ecology and seawater composition from such data require knowledge about species-specific compositions of well-preserved calcitic fossils. Comprehensive datasets, recording averages, intraspecimen and intraspecific variability of geochemical proxies in fossil calcite, however, are still largely lacking. Here we report δ 13 C and δ 18 O values, as well as Mg/Ca, Sr/Ca and Mn/Ca ratios of 204 aliquots sampled along transects through three rostra of the late early Campanian belemnite species Belemnellocamax mammillatus . Geochemical signatures of partially altered samples are consistent to those reported for early marine calcite cementation and show trends towards moderately higher Mn/Ca, heavier δ 13 C and lower Sr/Ca. In contrast, Mg/Ca ratios and δ 18 O values remain similar to projected original values. Median δ 18 O values of − 0.3 to 0.0‰ are comparable to the heaviest values of coeval oysters from the same localities, and internal variability of the well-preserved parts of the rostra is low. These findings suggest that B . mammillatus lived mostly in the deep part of the basin where seasonal changes were low and water temperatures cool. The δ 13 C is offset from oysters and most coeval belemnite species from the same region, and from bulk rock values of other European localities by several permil towards lighter values. This offset suggests that a strong vital effect impacted the carbon isotopes of the investigated species during calcification. Average Mg/Ca ratios of 11.5 mmol/mol and Sr/Ca ratios of 2.13 mmol/mol (n = 155) are found for the well-preserved parts of the belemnite rostra. The intraspecimen variability of Mg/Ca and Sr/Ca ratios between 7 and 20% (2 relative standard deviations) is similar amongst the specimens, but intraspecific variability of Mg/Ca is significantly higher than for Sr/Ca. Average Sr/Ca ratios of 2.1 ± 0.2 mmol/mol and Mg/Ca of 11 ± 3 mmol/mol are proposed for the late early Campanian B . mammillatus of the Kristianstad Basin. [ABSTRACT FROM AUTHOR]

Continuous and biostratigraphically well-constrained carbon isotope (δ13C org) profiles through the upper Miaolingian (middle Cambrian) to Tremadocian (Lower Ordovician) part of the Alum Shale Formation in four drill cores from southernmost Scandinavia are described. The sections record seven Furongian (upper Cambrian) excursions/spikes, of which three appear valuable as auxiliary markers for identifying global stage boundaries. The Steptoean Positive Carbon Isotope Excursion (SPICE) event with a magnitude of up to 2.8‰ is located mainly within the Olenus Superzone. The onset, as specified here, coincides with the end-Marjuman extinction and is marked by a minor negative excursion (up to −1.6‰) right below the Miaolingian–Furongian boundary. The end of the SPICE event approximates the upper boundary of the Olenus Superzone and has potential for correlation of the Paibian–Jiangshanian boundary. The Top of Cambrian Excursion (TOCE) with a magnitude of about −1.6‰ straddles the Parabolina lobata – Parabolina heres megalops zonal boundary in Baltoscandia. This chemostratigraphic excursion, considered as a synonym of the Hellnmaria-Red Tops Boundary excursion (HERB), represents a secondary marker for correlating the base of Stage 10, if defined by the FAD of Eoconodontus notchpeakensis. A positive spike at the Cambrian–Ordovician boundary, here named COBS, recognized in the stratotype section at Green Point (Canada; δ13C carb magnitude +5.3‰), Scandinavia (δ13C org magnitude up to +2.2‰) and elsewhere, appears as a valuable supplementary marker for recognizing this important boundary. The described δ13C org profile from the Albjära-1 core provides a standard reference for Furongian carbon isotope chemostratigraphy in Baltica, refines the correlation between Baltica and other palaeocontinents, and indicates new possibilities for pinpointing international stage boundaries within the Furongian based on carbon isotope records. • First biostratigraphically well-constrained δ13C org data for the entire Furongian of Baltica • Global chemostratigraphic correlation of middle Cambrian to lowermost Ordovician successions • Pinpointing global Furongian stage boundaries based on δ13C events [ABSTRACT FROM AUTHOR]

• The Upper Cretaceous-Paleogene stratigraphy of the western Tajik Basin sequence. • Dating the western Tajik Basin using Sr-isotope and biostratigraphy. • Emplacement of the OAE2 and PETM within the western Tajik Basin sequence. • Deciphering the major and minor sea level cycles in the western Tajik Basin sequence. The Tajik-Afghan Basin is a large basin in Central Asia, whose sediments document the area's long tectonic and climatic history from the Paleozoic to the present. However, the sedimentary characteristics and stratigraphy of these successions remain poorly understood. The study of this basin is critical for understanding the depositional conditions that prevailed during the transformation of this area from a part of the Western Oceanic Tethys to a more restricted Para-Tethys. In the southwestern corner of the Tajik Depression, a well-exposed sedimentary sequence associated with a large anticlinal limb was sampled. The authors proposed a new age model based on a combination of biostratigraphic data from planktic foraminifera, calcareous nannofossils, and strontium chemostratigraphy (87Sr/86Sr). The lower part of the studied section is of the upper Cenomanian age (95.5 Ma), while the upper part is assigned to the early Oligocene age (34.05 Ma). The carbon isotope profile shows several excursions linked to major paleoenvironmental events including the Oceanic Anoxic Event 2 (OAE2) and the Paleocene-Eocene Thermal Maximum (PETM). The latter is revealed in the study area for the first time. New sedimentological observations and interpretations of the depositional environments and sea-level cycles are provided. The deposition in the Aktash area occurred between upper coastal lagoonal and transitional environments before fully transitioning to continental environments in the Neogene. The stratigraphic record in Aktash is divided into large-scale progradation/ retrogradation cycles that can be tentatively linked to global sea-level signals. [ABSTRACT FROM AUTHOR]

The Poigny borehole near Provins (Seine-et-Marne) provides the most complete single pristine section through the Upper Cretaceous Chalk of the Paris Basin. A well preserved and diverse palynoflora including 236 species and subspecies of organic-walled dinoflagellate cysts (dinocysts) is documented from the borehole, together with a high-resolution carbon-isotope curve (δ13Ccarb) for the Coniacian-Campanian interval. Integration of the palynological and δ13Ccarb data provides a basis for a chemostratigraphic and biostratigraphic correlation to England and Germany. Carbon isotope events (CIEs) are used to refine the placement of sub-stage boundaries in the core, and to calibrate and correlate distinctive palynological events with those from other European sections. Thirty-three palynological events in the upper Coniacian-Campanian, judged to be of biostratigraphic significance, are described. Palynological assemblages, the peridinioid/gonyaulacoid (P/G) dinocyst ratio and clay mineralogy are compared to depositional sequences and implicate sea-level as a major driver of palaeoenvironmental change. [ABSTRACT FROM AUTHOR]

The duration of polarity Chron C31r is estimated with a cyclostratigraphic approach. Two sites are investigated: ODP Site 762 (Indian Ocean) and the Contessa Highway section (Gubbio, Italy). Cyclostratigraphic analysis is performed on greyscale variations (Site 762) and magnetic susceptibility variations (Contessa section). Both sites reveal an astronomical control of the sedimentation, highlighted by the identification of all the orbital periodicities. Cyclostratigraphic signals are tuned on 405 ka eccentricity cycles extracted from the La04 astronomical solution. In both sites, cycle counting gives an estimate of the duration of polarity Chron C31r of about 2.09 ± 0.03 Ma. [ABSTRACT FROM AUTHOR]

Abstract: We study the problem of designing truthful algorithms for scheduling a set of tasks, each one owned by a selfish agent, to a set of parallel (identical or unrelated) machines in order to minimize the makespan. We consider the following process: at first the agents declare the length of their tasks, then given these bids, the protocol schedules the tasks on the machines. The aim of the protocol is to minimize the makespan, i.e. the maximum completion time of the tasks, while the objective of each agent is to minimize the completion time of its task and thus an agent may lie if by doing so, his task may finish earlier. In this paper, we show the existence of randomized truthful (non-polynomial-time) algorithms with an expected approximation ratio equal to for different scheduling settings (identical machines with and without release dates and unrelated machines) and models of execution (strong or weak). Our result improves the best previously known result Angel et al. (2006)  for the problem with identical machines () in the strong model of execution and reaches, asymptotically, the lower bound of Christodoulou et al. (2007) . In addition, this result can be transformed to a polynomial-time truthful randomized algorithm with an expected approximation ratio (resp. ) for (resp. ). [Copyright &y& Elsevier]

Upper Cretaceous marine sequences in the Gulf Coastal Plain (USA) span the Cretaceous–Paleogene (K–Pg) transition, allowing for detailed studies of one of the most severe extinction events of the Phanerozoic. To improve the temporal resolution of the stratigraphic record that represents environmental change leading up to the K–Pg boundary, we constructed a high-resolution chemostratigraphy and cyclostratigraphy of upper Maastrichtian shallow marine deposits located in the state of Mississippi (USA). Upper Maastrichtian strata in this area consist of alternating decimeter scale chalk and marl rhythmites deposited in a hemipelagic setting. New geochemical proxy records were used to test whether rhythmic sedimentation was driven by Milankovitch cycles. Stable isotopes (δ13C carb , δ18O carb), carbonate content (wt% CaCO 3), and elemental concentrations (Ti, K, Fe) integrated with microfossil and ammonite biostratigraphy reveal astronomical forcing in the studied record. Spectral estimation suggests that rhythmic bedding was associated with climate change driven by precession (~20 kyr). Obliquity signals are also apparent in our analysis, and short eccentricity (~100 kyr) is inferred from amplitude modulation of precession. Studied sections were correlated at the precession scale with the recently tuned K–Pg succession near Morello, Italy which is stratigraphically equivalent to the well-characterized K–Pg sites in Gubbio, Italy (Bottaccione, Contessa Highway). Additionally, carbon isotope records from the study area exhibit large scale trends throughout the latest Maastrichtian, similar to those observed in the Morello and Bottaccione sections. Thus, we show that Milankovitch-scale climatic signals and low-amplitude carbon isotope shifts (<0.5‰) of the late Maastrichtian of the Gulf Coastal Plain are well-preserved and can be correlated globally. • A high-resolution chemostratigraphy was constructed for the Prairie Bluff Chalk. • Milankovitch cycles are preserved in Latest Cretaceous chalks in Mississippi. • Carbon isotope records from the Prairie Bluff Chalk may represent a global signal. [ABSTRACT FROM AUTHOR]

We report on new collections of cephalopods (ammonites and nautilids) from the Cretaceous-Paleogene (K-Pg) successions of the Corsicana and Kincaid formations exposed along the Brazos River in Falls County, Texas. An abundant fauna of eight species comprising four genera of ammonites is described from the Corsicana Formation, including Discoscaphites mullinaxorum n. sp. The presence of abundant aptychi (probably lower jaws) of Discoscaphites and Eubaculites, as well as juvenile specimens, indicates a living population that experienced little postmortem drift. The lytoceratid genus Gaudryceras is also reported for the first time from the Brazos River area. Presence of the index taxon Discoscaphites iris (Conrad, 1858) indicates that the fauna belongs to the D. iris Range Zone, the highest ammonite range zone in North America. Correlation with new and existing microfossil data indicates that the fauna represents the uppermost Maastrichtian, and comparison with published records further suggests that this is the most diverse D. iris Zone fauna yet reported from the Gulf and Atlantic Coastal Plains of North America. Three ammonite genera are recorded from the basal units of the K-Pg event deposit at Brazos, which likely represents deposition in the immediate aftermath of the Chicxulub impact event. A single specimen of the nautilid Eutrephoceras is reported from the Danian Kincaid Formation, less than 300 kyr after the K-Pg boundary. These data provide new information on the differing fate of these cephalopod groups during the K-Pg mass extinction and add to the picture of diverse and abundant Maastrichtian ammonite faunas prior to the Chicxulub impact event. [ABSTRACT FROM AUTHOR]