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Abstract: High-resolution carbon isotope stratigraphy of the upper Campanian–Maastrichtian is recorded in the Boreal Realm from a total of 1968 bulk chalk samples of the Stevns-1 core, eastern Denmark. Isotopic trends are calibrated by calcareous nannofossil bio-events and are correlated with a lower-resolution δ13C profile from Rørdal, northwestern Denmark. A quantitative approach is used to test the reliability of Upper Cretaceous nannofossil bio-events and provides accurate biohorizons for the correlation of δ13C profiles. The Campanian–Maastrichtian boundary (CMB) is identified through the correlation of dinoflagellate biostratigraphy and δ13C stratigraphy between Stevns-1 and the Global boundary Standard Stratotype-section and Point at Tercis les Bains (SW France), allowing the identification of new chemical and biostratigraphic markers that provide a precise placement of the stage boundary on a regional scale. The boundary interval corresponds to the third phase of a stepwise 0.8‰ negative δ13C excursion, lies in calcareous nannofossil subzone UC16dBP, and encompasses the last occurrence of nannofossil Tranolithus stemmerikii and first occurrence of nannofossil Prediscosphaera mgayae. Fifteen δ13C events are defined and correlated to sixteen reliable nannofossil biohorizons, thus providing a well-calibrated standard high-resolution δ13C curve for the Boreal Realm. [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]

This paper is dedicated to the connection, by a provider, of multiple groups of nodes spread over a network. The role of the provider is to interconnect the members of every group. For this purpose, it must distribute the available links of the network between the groups. The general aim then is to allocate these links in such a way that the communications latencies in the allocated structure are equivalent to the ones in the original (full) network for each group. We study two approaches constructing structures preserving the maximum latency (called the diameter). Unfortunately we show that the associated optimization graph problems are difficult (one cannot be approximated by a constant and the other is NP-complete). Due to these difficulties we relax the constraint on the diameter and propose to construct a unique tree connecting all the groups together. We give a heuristic to treat this problem and we propose several analytical results on its maximum and average latencies performance. [ABSTRACT FROM PUBLISHER]

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]

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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 early Eocene (c. 56 - 48 million years ago) experienced some of the highest global temperatures in Earth's history since the Mesozoic, with no polar ice. Reports of contradictory ice-rafted erratics and cold water glendonites in the higher latitudes have been largely dismissed due to ambiguity of the significance of these purported cold-climate indicators. Here we apply clumped isotope paleothermometry to a traditionally qualitative abiotic proxy, glendonite calcite, to generate quantitative temperature estimates for northern mid-latitude bottom waters. Our data show that the glendonites of the Danish Basin formed in waters below 5 °C, at water depths of <300 m. Such near-freezing temperatures have not previously been reconstructed from proxy data for anywhere on the early Eocene Earth, and these data therefore suggest that regionalised cool episodes punctuated the background warmth of the early Eocene, likely linked to eruptive phases of the North Atlantic Igneous Province. The early Eocene was characterized by exceptionally high global temperatures and no polar ice. Here, clumped isotope paleothermometry of glendonite calcite from the Danish Basin shows that these were formed in waters below 5 °C, indicating that regionalised cool episodes punctuated the background warmth of the early Eocene. [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]

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]

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]

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]

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]

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]

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]

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]

A 460 m long profile of the Cretaceous-Paleogene (K-T) boundary strata at Stevns Klint was measured by the late Professor A. Rosenkrantz probably in 1944. The measured profile was inherited by Finn Surlyk around 1974 together with other original boundary data. This material was dug up in a long-forgotten drawer in connection with detailed field work by the co-authors on the boundary succession in the late spring and summer of 2021. The profile illustrates the stratigraphy, geometry and palaeotopography of the boundary strata in unprecedented detail. The part of the cliff illustrated in the profile is today partly covered by beach ridges composed of flint rubble but is situated below the finest section of the lower Danian bryozoan mounds exposed at Stevns Klint. This coastal section is situated immediately adjacent to a large limestone quarry and was planned to be quarried away around 1937, but was saved by A. Rosenkrantz who demonstrated its great scientific and educational value to the authorities. [ABSTRACT FROM AUTHOR]

• Discovery of Milankovitch cycles in the late Cambrian from two coeval drill cores. • Climate cycles are recorded by XRF in pyrite and clay-bound elements. • We establish a floating astronomical time scale across 8.9 My including the SPICE event. • Sedimentation rate is anticorrelated with eustatic sea level. • Precise constraint on Earth-Moon distance, lunar recession and day length ∼493 Ma. We report evidence for Milankovitch cycles in two drill cores from the Cambro–Ordovician Alum Shale Formation of Scandinavia. The signal is preserved in elemental abundances recorded at high stratigraphic resolution by core scanning XRF analysis (0.2 mm resolution). The new data enable us to establish a floating timeline calibrated to the stable 405 kyr eccentricity cycle for a ∼8.7 Myr interval across the Miaolingian–Furongian boundary. This interval spans the Steptoean Positive Carbon Isotope Excursion (SPICE), which is recorded in the δ 13 C org in the studied drill cores. We calculate the durations of the Olenus Superzone to 3.4 ± 0.2 Myr, the Parabolina Superzone to 1.9 ± 0.3 Myr, the Leptoplastus Superzone to 0.33 ± 0.18 Myr, the Protopeltura Superzone to 0.51 ± 0.20 Myr, and the SPICE event straddling the Paibian and lower main part of the Jiangshanian Stage to 3.0 ± 0.2 Myr. The sedimentation rate shows similar trends at both drilling locations and is inversely correlated to eustatic sea level changes in certain time intervals, opening tantalizing new prospects of using cyclostratigraphic analyses of shales to track eustatic sea level variations. The identification of obliquity cycles enables us to calculate the Cambrian Earth–Moon distance as well as the day length at ∼493 Ma to 368.9 ± 2.3 ⋅ 106 m and 21.78 ± 0.29 hr, respectively. [ABSTRACT FROM AUTHOR]