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A detailed biostratigraphic, chemostratigraphic, and chronostratigraphic study was carried out in the South‐Western margin of the Neo‐Tethys ocean (Tunisia) covering the Eocene‐Oligocene interval to report potential paleoenvironmental and paleoclimatic changes associated with the growth of the Antarctic ice sheet (AIS). The studied section consists of marls and limestones extending from the Helicosphaera compacta nannofossil Zone (CNE21) to the Reticulofenestra umbilicus Zone (CNO2). The Bc of Clausicoccus subdistichus coincides in northeastern Tunisia with the extinction of hantkeninids and is thus used here to define the Eocene/Oligocene boundary (EOB) at 34.03 Ma. Calcareous nannofossil assemblages suggest a significant change from oligotrophic/warm surface waters during the late Eocene to eutrophic/cool waters during the early Oligocene. The observed changes in trophic conditions are synchronous with a shallowing trend testified by an increase in nearshore species and enhanced terrigenous input. Major environmental changes occurred at the EOB and across glaciation event Oi‐1a whereas we record a poor imprint of glaciation event Oi‐1. Three orbital configurations have been distinguished: (1) The late Eocene is characterized by a prominent 405‐kyr cycle and a weak obliquity component; (2) the onset of cooling at 34.35 Ma coincides with the rosette‐shaped discoaster extinction and is reflected by a shift toward enhanced obliquity and short‐eccentricity cycles. The installation of a fully developed AIS (event Oi‐1a, 32.75 Ma) shows the most pronounced obliquity imprint reflecting an increased influence of high‐latitude climate processes; (3) after 31.75 Ma, the obliquity decreases in coincidence with the return to a dominant long‐eccentricity cycle. Plain Language Summary: The Eocene/Oligocene transition corresponds to one of the most important climatic shifts in the Cenozoic. This paleoclimatic shift from the greenhouse of the late Eocene to the icehouse regime in the early Oligocene triggered changes in the paleoenvironmental conditions of the Neo‐Tethyan area. We used calcareous nannofossil assemblages, carbon isotopes, elemental data (X‐ray fluorescence), and spectral analysis applied on magnetic susceptibility to report the possible effects of ice volume changes associated with the Antarctic glaciation on the Southern Neo‐Tethyan region and on the expression of Milankovitch cycles at low latitudes. We observe a change in the calcareous nannofossil assemblages that suggests a transition from low‐nutrient/warm‐water conditions to more heterotrophic/cooler conditions across the Eocene/Oligocene interval associated with the shift from a dominant 405‐kyr long‐eccentricity cycles to a prevalent obliquity and short‐eccentricity forcing. However, the situation shifted again at 31.75 Myr, with the return of dominant long‐eccentricity cycles. Key Points: High phytoplankton productivity across the EOT of the Southern Neo‐Tethys (Tunisia)Astronomical calibration of the Tunisian record and power variations in the expression of distinct orbital components across the EOTMajor changes in trophic conditions and sediment composition at the EOB and across Oi‐1a but minor changes across the main Oi‐1 glaciation [ABSTRACT FROM AUTHOR]

The Toarcian Oceanic Anoxic Event (T-OAE, ∼183 Ma) was characterized by enhanced carbon burial, a prominent negative carbon-isotope excursion (CIE) in marine carbonate and organic matter, and numerous geochemical anomalies. A precursor excursion has also been documented at the Pliensbachian/Toarcian boundary, but its possible causes are less constrained. The T-OAE is intensively studied in the Cleveland Basin, Yorkshire, UK, whose sedimentary deposits have been litho-, bio- and chemostratigraphically characterised. Here, we present new elemental data produced by hand-held X-ray fluorescence analysis to test the expression of redox-sensitive trace metals and detrital elements across the upper Pliensbachian to mid-Toarcian of the Cleveland Basin. Detrital elemental concentrations (Al, Si, Ti, Zr) are used as proxies for siliciclastic grain content and thus, sea-level change, which match previous sequence stratigraphic interpretations from the Cleveland Basin. The timescale of the event is debated, though our new elemental proxies of relative sea level change show evidence for a cyclicity of 350 cm that may be indicative of ∼405 kyr eccentricity cycles in Yorkshire. Trends in total organic carbon and redox-sensitive elements (S, Fe, Mo, As) confirm scenarios of widespread ocean deoxygenation across the T-OAE. The correlation of comparable trends in Mo across the T-OAE in Yorkshire and the Paris Basin suggests a similar oceanic drawdown of this element accompanying widespread anoxia in the two basins. Data from Yorkshire point to a transgressive trend at the time of the Mo drawdown, which contradicts the “basin restriction” model for the euxinic conditions that characterise the CIE interval. [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]

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

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]

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]

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]

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]

Abstract: Recent improvements to astronomical modeling of the Solar System have contributed to important refinements of the Cenozoic time scale through astronomical calibration of sedimentary series. We extend this astronomical calibration into the Cretaceous, on the base of the 405ka orbital eccentricity variation thanks to the recovery of well preserved Maastrichtian sedimentary series from ODP (Ocean Drilling Program) Holes 1258A (Leg 207, Equatorial Atlantic), 1267B (Leg 208, South Atlantic), 762C (Leg 122, Indian Ocean) and DSDP (Deep Sea Drilling Program) Hole 525A (Leg 74, South Atlantic). Cyclostratigraphic analysis is performed on high resolution measurements of magnetic susceptibility on sediments cored during Legs 207 and 208, and gray level variations of sediment color obtained from core photographs from Legs 122 and 74. Astronomical control on sedimentation is evident at every site, with the presence of cycles corresponding to forcing by precession, obliquity and orbital eccentricity variations. Identification of these cycles leads to the definition of a detailed cyclostratigraphic frame covering nearly 8Ma, from the upper Campanian to the Cretaceous/Paleogene (K/Pg) boundary. Durations of each magnetochron from C32r.2r to C29n are inferred by cycle counting. Astronomical calibrations of Maastrichtian sedimentary series are proposed, based on the 405ka eccentricity variation according to the most recent astronomical solution La2010a. Two different ages are suggested for the K/Pg boundary, considering the uncertainty of the long-term variation of the 405ka eccentricity cycle. The first proposal provides a Cretaceous/Paleogene boundary age of 65.59±0.07Ma and the second an age of 66±0.07Ma, which is coherent with the most recent radio-isotopic datings. Magnetochron boundaries and the Campanian/Maastrichtian boundary are dated relative to these numerical ages of the K/Pg boundary. [Copyright &y& Elsevier]

Mercury (Hg) anomalies linked to Large Igneous Provinces (LIP) volcanism have been identified in sediments across all five major mass extinctions in Earth's history. This study tests whether Hg in marine sediments is a reliable proxy linking Deccan Traps volcanic eruptions to late Maastrichtian global climate warming and the mass extinction at the Cretaceous-Paleogene boundary (KPB). Our primary test site is the Elles section in Tunisia, the auxiliary Global Stratotype Section and Point (GSSP) to El Kef. Elles has the most complete marine sedimentary record and a high average sedimentation rate of ~4.7 cm/ky. We chose the Hor Hahar section in Israel to corroborate the geographic distribution of Hg fallout from Deccan volcanism. Reliability of the Hg proxy over the last 550 ky of the Maastrichtian to early Danian was evaluated based on high-resolution age control (orbital cyclostratigraphy), stable isotope climate record, Hg concentrations, biotic turnover and mass extinction. These results were correlated with the pulsed Deccan eruptive history constrained previously by U-Pb zircon geochronology. Our results support Hg as robust proxy for Deccan volcanism with large Hg spikes marking "extreme event" (EE) pulsed eruptions correlative with climate warming peaks separated by steady, less intense eruptions. Long-term global climate warming began near ~350 ky pre-KPB, reached maximum warming (3–4 °C) between 285 and 200 ky pre-KPB, followed by gradual cooling and rapid temperature drop between 45 and 25 ky pre-KPB. During the last 25 ky before the KPB, multiple Hg EE eruptions correlate with hyperthermal warming that culminated in the rapid mass extinction at Elles during ≤1000 years of the Cretaceous. These latest Cretaceous Hg peaks may correlate with massive, distal, Deccan-sourced lava flows (>1000 km long) that traversed the Indian subcontinent and flowed into the Bay of Bengal, bracketing the mass extinction. These results support Deccan volcanism as a primary driver of the end-Cretaceous mass extinction. Unlabelled Image • Hg anomalies in sediments are a reliable proxy for Deccan volcanism. • Deccan eruptions caused long-term climate warming in the last 350 ky of the Cretaceous. • Long-term climate warming resulted in faunal decline but no extinctions. • Paroxysmal Deccan eruptions occurred during the last 25 ky of the Cretaceous. • Deccan-induced hyperthermal and ocean acidification led to the KPB mass extinction. [ABSTRACT FROM AUTHOR]