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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 (${\delta }^{13}$C$_{\mathrm{carb}}$) for the Coniacian–Campanian interval. Integration of the palynological and ${\delta }^{13}$C$_{\mathrm{carb}}$ 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.

The Cambrian is the most poorly dated period of the past 541 million years. This hampers analysis of profound environmental and biological changes that took place during this period. Astronomically forced climate cycles recognized in sediments and anchored to radioisotopic ages provide a powerful geochronometer that has fundamentally refined Mesozoic–Cenozoic time scales but not yet the Palaeozoic. Here we report a continuous astronomical signal detected as geochemical variations (1 mm resolution) in the late Cambrian Alum Shale Formation that is used to establish a 16-Myr-long astronomical time scale, anchored by radioisotopic dates. The resulting time scale is biostratigraphically well-constrained, allowing correlation of the late Cambrian global stage boundaries with the 405-kyr astrochronological framework. This enables a first assessment, in numerical time, of the evolution of major biotic and abiotic changes, including the end-Marjuman extinctions and the Steptoean Positive Carbon Isotope Excursion, that characterized the late Cambrian Earth. The Cambrian is the most poorly dated period of the past 541 million years. Here, the authors present a new astronomical time scale, allowing for a first assessment, in numerical time, of the evolution of major biotic and abiotic changes that characterized the late Cambrian Earth. [ABSTRACT FROM AUTHOR]

The current study presents new bed‐by‐bed brachiopod δ13C and δ18O records from Öland, Sweden, which together with previously published data from the East Baltic region, constitutes a high‐resolution paired brachiopod and bulk rock carbon and oxygen isotope archive through the Lower to Upper Ordovician successions of Baltoscandia. This new data set refines the temporal control on the global Ordovician δ18O‐trend considerably, improving paleoenvironmental reconstructions through the main phase of the Great Ordovician Biodiversification Event (GOBE). The new brachiopod carbon and oxygen isotope records from Öland display strong similarity with the East Baltic records, elucidating the regional consistency as well as global correlation utility of the ensuing composite Baltoscandian Lower to Middle Ordovician carbon and oxygen isotope record. The carbon isotope record from Öland indicates that the widely reported Middle Ordovician carbon cycle perturbation—MDICE (Mid‐Darriwilian Carbon Isotope Excursion)—is recorded in both brachiopods and bulk carbonates. The oxygen isotope record reveals a long‐term Lower to Upper Ordovician trend of increasingly heavier brachiopod δ18O values, with a pronounced increase during the Middle Ordovician Darriwilian Stage. We interpret this trend as dominantly reflecting a paleotemperature signal indicating progressively cooler Early to Middle Ordovician climate with glacio‐eustasy. Our Baltic δ18O values are therefore consistent with postulations that the biotic radiations during the GOBE and climatic cooling during the Darriwilian were strongly linked. Plain Language Summary: Oxygen isotope values obtained from fossil brachiopod shells have traditionally been used as a faithful paleoclimatic proxy to shed light on temperature trends in ancient oceans. However, because brachiopod shells are susceptible to diagenetic overprint after burial, secular oxygen isotope trends derived from these fossils are often questioned—notably the farther one goes back in geological time. This study presents temporally well‐resolved oxygen isotope data from Lower–lower Upper Ordovician sedimentary rocks of Öland, Sweden, tied precisely to conodont biostratigraphy on the bed‐by‐bed scale. This interval is important in Earth history as it brackets the greatest marine biodiversification event known in the fossil record and coincides with a global climatic cooling phase (determined based on proxies other than oxygen isotopes). The current study therefore provides an excellent test of the spatial and temporal consistency of the secular Ordovician oxygen isotope trend. We find that although our data is probably affected by diagenetic modification, primary paleoclimatic signals are preserved. Furthermore, as current global Ordovician oxygen isotope records lack sufficient resolution because they comprise data from geographically widely distributed low‐paleolatitude localities, our new high‐resolution data set from one mid‐paleolatitude region, provides significant temporal insights that considerably improves our understanding of the Ordovician climate. Key Points: New paired Baltic carbonate data set improves Ordovician 18O‐ and 13C‐recordThe new data supports a Middle Ordovician sea surface temperature coolingRegional/intra‐basinal consistency of oxygen isotope trends indicate primary nature of paleoenvironmental changes [ABSTRACT FROM AUTHOR]

Abstract The Upper Cretaceous Flamborough Chalk Formation of the English Northern Chalk Province (Danes Dyke section, East Yorkshire, UK) has been sampled for isotope analyses to test for the expression of the positive carbon-isotope excursion defining the Santonian–Campanian Boundary Event (SCBE) in northern England, and to improve basin-scale correlations between the Boreal and Tethyan realms. Clay mineral investigations have been conducted in order to characterise potential variations in the detrital flux between the top of the Santonian and the base of the Campanian, and to test relationships with the SCBE. In the Flamborough Chalk and in other chalk sections, the Santonian/Campanian boundary is defined by the highest occurrence datum of the crinoid Marsupites. Carbon isotope results in this section indicate the presence of the negative Foreness Event in the upper Santonian, while the SCBE is characterised by a double positive excursion with peaks respectively named 'a' and 'b'. The first peak of the SCBE (a) lies in the uppermost part of the Marsupites Zone and therefore belongs to the upper Santonian. Peak b of the SCBE is located above the highest occurrence of Marsupites and is thus partially included in the Uintacrinus anglicus Zone of the lower Campanian. The clay fraction (<2 μm) analysis of chalks and marl bands reveals dominant smectite-rich clay minerals (e.g. R0 type illite/smectite mixed-layers or IS R0, 95% on average) and subordinate illite (5% on average) through the section. A discrete increase of the illite/IS R0 ratio in the clay fraction, combined with an increase in marl horizons and clay proportions in the bulk insoluble residue, highlight slightly enhanced terrigenous input during the SCBE. Correlation with published key sections in Western Europe shows that the SCBE has a similar chemostratigraphic signature and can be used to refine regional correlations, although it is thicker in the English Northern Province due to higher sedimentation rates in this area. [ABSTRACT FROM AUTHOR]

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

An integrated biostratigraphic (foraminifera, calcareous nannofossils, crinoids), chemostratigraphic (stable carbon isotopes) and magnetostratigraphic study of the Bocieniec section (southern Poland) is presented here. The section presents a continuous and lithologically monotonous sedimentary record across the Santonian–Campanian boundary transition. A large number of macrofossil, foraminiferal and calcareous nannofossil bioevents along with several well-identified carbon-isotope excursions of the upper Santonian and lowermost Campanian are documented. The base of the Campanian is well-constrained by the last occurrence (LO) of the crinoid Marsupites testudinarius , and correlates to the onset of the first δ 13 C positive peak of the Santonian–Campanian Boundary Event (SCBE peak a). A presumable primary Cretaceous paleomagnetic signal highlights the potential presence of the C34N/C33R magnetic reversal although its exact position remains uncertain between peaks a and b of the SCBE. The planktic foraminifer Dicarinella asymetrica is very rare at Bocieniec but a potential LO of this important marker may be recorded in coincidence with peak b of the SCBE. The first occurrence (FO) of calcareous nannofossil Broinsonia parca parca coincides with the lower part of chron C33R and with the early Campanian pilula zone event. A large set of additional nannofossil events and benthic foraminifer events further constrain the stratigraphy of the section and along with the carbon isotopes, allows for correlation with other important sections of the Boreal realm. Although the Bocieniec section is relatively thin and condensed (5.5 m), the successive order of events and presence of all past proposed stratigraphic criteria for the Santonian-Campanian boundary makes it the most complete reference section for this interval at the European and at the global scale. Moreover, this section allows for a precise correlation of the Tethyan and Boreal domains. The Bocieniec section fulfils the geological criteria to be a potential boundary stratotype candidate for the base of the Campanian Stage. [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]

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]

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: 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]

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]

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]

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]

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]

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]

• 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]

The Middle Ordovician (~460-470 Ma) in Baltoscandia is mainly represented by the so called 'orthoceratite limestone'. This is a geographically wide-spread condensed sedimentary succession of a few tens of meters thickness consisting of fine-grained limestones deposited at middle paleolatitudes. These successions have a long history of detailed litho- and biostratigraphical research, which in recent years is complemented with chemostratigraphical investigations (mainly stable carbon isotopes). New mm-resolution XRF elemental core scanning data from the Tingskullen-1 and Kårehamn P4 cores from the island of Öland, Sweden, reveal the potential to further test the hypothesis of the presence of Milankovitch scale cyclicity in these records. This new high-resolution data also resolves the regular occurrence of hardgrounds in this 'orthoceratite limestone', as for example expressed in minima in carbonate content and peaks in detrital elements. These dissolution surfaces have been suggested to be related to carbonate production-dissolution alternations. It is interesting that many of the relative changes in the elemental profiles seem to be related to these dissolution horizons and show a certain regularity in occurrence on different spatial levels. The ratio between the different periods, in combination with specific patterns of amplitude modulation - both visually and statistically inspected - suggests the presence of a precessional scale variability, bundled in eccentricity cycles. Besides the existing integrated stratigraphical framework, these interpretations can be tested by ongoing geochronological work (CA-TIMS U-Pb dating of zircons from volcanic ash layers present in these successions). The prospective of building an astronomical timescale for the Middle Ordovician can shed new light on its climate dynamics and associated tempo and duration of important events such as the Great Ordovician Biodiversification Event (GOBE) and the middle Darriwilian carbon isotope excursion (MDICE). [ABSTRACT FROM AUTHOR]

The Aalenian was a time marked by profound environmental and carbon cycle changes. Still, the scarcity of detailed studies hinders a better understanding of the triggering mechanisms and the larger-scale context of Lower to Middle Jurassic environmental perturbations. This study provides an unprecedented high-resolution biostratigraphically well-constrained carbon isotope record (δ 13C org and δ 13C carb) for the upper Toarcian–lower Bajocian interval of two expanded limestone-marl alternation successions in France (French Subalpine Basin) and Chile (Andean Basin). The comparison with available records from the Tethyan and Boreal domains highlights that medium-term carbon isotope fluctuations are reproducible across different palaeoceanographic settings from both hemispheres, providing for the first time compelling evidence for recurrent perturbations of the global carbon cycle during the Aalenian. Combined with a review of geological events, climate modes, abundance and diversity of major fossil groups, and trophic conditions inferred from the calcareous nannofossil record, our study fills the gap in our understanding of global environmental changes in a so-far poorly documented Middle Jurassic stage, intercalated between the early Toarcian Oceanic Anoxic Event and the early Bajocian carbonate crisis. Importantly, this compilation indicates that the Aalenian was a pivotal time interval of environmental perturbations, likely triggering the Mesozoic Marine Revolution. • Recurrent global carbon cycle perturbations during the Aalenian • Evolutionary and ecological changes indicate a major middle–late Aalenian event. • The Aalenian event catalysed the Bajocian event and the Mesozoic Marine Revolution. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Gurpi Fm. age in SW Lurestan (Iran) is restricted to late Campanian-early Danian. • Gurpi facies variations in Lurestan were mostly controlled by tectonics. • The Lopha limestone in SW Lurestan shows the position of the forebulge. • Subaerial exposure of carbonate platforms led to persistent fine-fraction reworking. • Basin subsidence caused high sedimentation rates in late Maastrichtian- early Danian. In order to investigate the depositional history and facies architecture of the Campanian-Danian interval of the Zagros Basin, the succession of the Gurpi Formation (Fm.) was examined in the Gandab section, southwestern Lurestan Province, through an integrated study of calcareous nannofossils, planktic foraminifera, and bulk carbonate carbon isotopes. Despite the persistent occurrence of reworked fine fraction carbonates as attested by microfossils across the investigated interval, the carbon isotope stratigraphy of Lurestan shows a good correlation with those in the eastern and western Tethys from the Shahneshin section in central Zargos (Fars Province) and Gubbio of northern Apennines in Italy (Gubbio). The succession can be assigned an age range from late Campanian to early Danian based on the integrated stratigraphy. The results from the Gandab section, as well as field observations in more northeasterly areas of Lurestan, point to lateral facies variation of the Campanian–Danian interval associated with tectonic activity during the Late Cretaceous-Paleogene of the Zagros Basin. According to the known distribution of facies across the SW-NE transect of Lurestan and detailed ages delineated in the Gandab section, a schematic model of syntectonic sedimentation and facies distribution is drawn. Our model illustrates how the continental convergence and closure of Neo-Tethys resulted in uplifting/subsiding of the basin floor, shifting in depocenter, significant changes in sedimentary facies, and reworking phenomena in the Lurestan region. [ABSTRACT FROM AUTHOR]

During the mid-Barremian (Early Cretaceous), the Boreal Realm experienced an episode of widespread deposition of laminated organic-rich black shales (Hauptblätterton in the Lower Saxony Basin, NW Germany and Munk Marl in the North Sea) which may correspond to a regional oceanic anoxic event (OAE). This study focuses on changes in exceptionally well-preserved calcareous nannofossil assemblages across the Munk Marl in two North Sea cores coupled with geochemical data (bulk carbonate stable isotopes and TOC). As calcareous nannofossils are highly sensitive to environmental changes in sea-surface waters, they are excellent proxies for palaeo-sea-water temperatures, for estimating proximal and distal settings as well as for characterising nutrient fluxes through fertility changes. No compelling carbon isotope excursion is associated with the Munk Marl but pronounced negative excursions are recorded across this interval in both investigated cores for oxygen isotopes with amplitudes of approximately 4 ‰ in the first core and 2.5 ‰ in the second. TOC values within the Munk Marl are generally very high, fluctuating between 1.82 WT% and 10.13 WT% with values peaking in its lower and upper thirds. The negative oxygen isotope excursions may indicate increasingly warmer water temperatures. Below the Munk Marl, the nannofossil assemblages are characterized by a relatively low abundance of oligotrophic indicators (W. barnesiae, Nannoconid spp.) and warm water indicators (C. margerelii, R. asper, W. britannica) while the fertility index taxa (B. constans, D. lehmanii, D. ignotus, Z. noeliae) and proximal indicators (Micrantholithus spp.) show high abundances. In the Munk Marl, generally, both the warm water and oligotrophic species increase in abundance while the fertility index taxa drop to very low numbers in the upper two-thirds. Moreover, we observe a three-fold subdivision of the Munk Marl in the nannofossil assemblage, which matches a similar subdivision in the TOC and carbonate content. The lower third of the Munk Marl shows higher abundances of W. barnesiae, warm water indicators and fertility index taxa, while the middle part is dominated by higher abundances of oligotrophic nannoconids and proximal indicators. The upper third is dominated by W. barnesiae and warm water indicators similar to the lower part, but with a contrasting low abundance of fertility index taxa. Above the Munk Marl, the warm water and oligotrophic indicators show relatively low abundances, while the proximal indicators increase again. The fertility index taxa also regain high abundances in one of the two investigated cores.We interpret these data as an expression of a very warm and arid climate during deposition of the Munk Marl, along with low nutrient influx and reduced terrigenous run-off. Stable warm and arid conditions favoured strongly reduced ocean mixing and enhanced stratification of the water column, which led to bottom water anoxia. [ABSTRACT FROM AUTHOR]