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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]

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]

Disentangling the external and internal forcing responsible for the variability of the Earth's climate and associated extreme events over the Holocene is crucial for producing reliable scenarios of adaptation to the effects of ongoing climate change. At mid-latitudes, significant relationships between westerly storminess, solar activity and internal atmospheric and oceanic modes of variability have been repeatedly evidenced to exist over millennial and centennial time scales. However, at shorter (decadal) scale, it is still challenging to establish clear control links between the forcing mechanisms and the spatio-temporal variability of past extra-tropical storms. This probably owes to the existence of complex multi-scale relationships and feedback loops, as well as to the difficulty of producing proxy-records of sufficiently high-resolution and wide spatial significance. Here we present a reconstruction of westerly storminess in western Denmark between 4840 and 2300 yrs. cal. B·P. Past-storminess is retrieved from an organic-rich sedimentary succession by combining markers of aeolian sand influx, μ-XRF geochemistry and plant macrofossils. Particular focus is paid to the c. 4840–4350 yrs. cal. B·P. period for which our record is characterized by a pluri-annual resolution. We evidence concurrent pluri-decadal shifts in storminess and humidity regime at our site that we interpret as relocations of the mean westerly storm-track over the North-Atlantic. The signal is dominated by ≈ 90, ≈ 50–80 and ≈ 35-yr periods, evoking possible links with solar activity, the North-Atlantic Oscillation (NAO), the Atlantic Multidecadal Oscillation (AMO) and the Atlantic Meridional Overturning Circulation (AMOC) modes of variability, respectively. The ≈ 35-yr periodicity found in our record is especially strong and stationary, suggesting that storminess could have been closely linked with the AMOC over the study period. Our records of storminess indeed show some great similarities with a record of deep overflow of a branch of the AMOC. Opposite to some model outputs, the strength of the AMOC seems to have often co-varied with storminess at pluri-decadal scales over the study period. We also find periods of high storminess activity to be significantly correlated with solar minima and relative pluri-decadal lows in the NAO. We suggest that small lowering in the strength of the NAO in an otherwise positive NAO context may have caused southward relocations of the mean westerly storm-track from subpolar latitudes to northern Europe. This invites to reconsider the importance given to using the NAO as a binary index. Finally, an attempt is made to explore the temporal lead-lag relationships between storminess and different potential forcing agents such as the Total Solar Irradiance, the NAO and the AMOC. Unfortunately, the insufficient chronological precision of the proxy-records available for the TSI, the NAO and the AMOC over the study period prevents us from deriving any robust interpretations regarding potential teleconnections at a decadal-scale between past north-Atlantic westerly storminess activity, solar forcing, the NAO and north-Atlantic surface and deep oceanic circulation. • Concurrent decadal shifts in north-eastern Atlantic storminess and precipitations • Storminess variability characterized by dominant non-coexistent 90, 55–80 and 35-yr periodicities. • Increased storminess during decadal to centennial minima in solar activity • Increased storminess during decadal relative lows in the NAO • Concurrent variations in storminess and strength of the AMOC [ABSTRACT FROM AUTHOR]

The Early Jurassic was broadly a greenhouse climate period that was punctuated by short warm and cold climatic events, positive and negative excursions of carbon isotopes, and episodes of enhanced organic matter burial. Clay minerals from Pliensbachian sediments recovered from two boreholes in the Paris Basin, are used here as proxies of detrital supplies, runoff conditions, and palaeoceanographic changes. The combined use of these minerals with stable isotope data (C-O) from bulk carbonates and organic matter allows palaeoclimatic reconstructions to be refined for the Pliensbachian. Kaolinite/illite ratio is discussed as a reliable proxy of the hydrological cycle and runoff from landmasses. Three periods of enhanced runoff are recognised within the Pliensbachian. The first one at the Sinemurian-Pliensbachian transition shows a significant increase of kaolinite concomitant with the negative carbon isotope excursion at the so-called Sinemurian Pliensbachian Boundary Event (SPBE). The Early/Late Pliensbachian transition was also characterised by more humid conditions. This warm interval is associated with a major change in oceanic circulation during the Davoei Zone, likely triggered by sea-level rise; the newly created palaeogeography, notably the flooding of the London-Brabant Massif, allowed boreal detrital supplies, including kaolinite and chlorite, to be exported to the Paris Basin. The last event of enhanced runoff occurred during the late Pliensbachian (Subnodosus Subzone of the Margaritatus Zone), which occurred also during a warm period, favouring organic matter production and preservation. Our study highlights the major role of the London Brabant Massif in influencing oceanic circulation of the NW European area, as a topographic barrier (emerged lands) during periods of lowstand sea-level and its flooding during period of high sea-level. This massif was the unique source of smectite in the Paris Basin. Two episodes of smectite-rich sedimentation (‘smectite events’), coincide with regressive intervals, indicating emersion of the London Brabant Massif and thus suggesting that an amplitude of sea-level change high enough to be linked to glacio-eustasy. This mechanism is consistent with sedimentological and geochemical evidences of continental ice growth notably during the Latest Pliensbachian (Spinatum Zone), and possibly during the Early Pliensbachian (late Jamesoni/early Ibex Zones). [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]

The Late Cretaceous is marked by geodynamical changes including Africa-Eurasia convergence that resulted in the narrowing of the Tethys Ocean and in ophiolite obduction along the southern margin of the various continental blocks in eastern Tethys. Geochemical and mineralogical analyses were performed on the Shahneshin section (Zagros Basin - eastern Tethys), to explore the consequences of this evolution on oceanic circulation, and to estimate the role of ophiolite weathering that can impact climate through atmospheric CO 2 drawdown. [Ni] and [Cr] sharply increase in the uppermost Campanian – Maastrichtian interval and are not coeval with an increase in the Nd isotope composition (ɛ Nd) of the detrital fraction of the sediments. This is interpreted as reflecting weathering of the mantellic, ultramafic part of the ophiolite sequence at that time, implying that ophiolites were exposed on the continents as soon as the Coniacian in the vicinity of the Zagros Basin. Hence their weathering could have contributed to the Late Cretaceous climatic cooling. Clay mineralogy reveals an alternation of kaolinite-rich humid periods (Coniacian/Santonian and late early Campanian to latest Campanian) and kaolinite-depleted arid periods (early Campanian and the latest Campanian to late Maastrichtian). The ɛ Nd(t) of bathyal waters (carbonate leached fraction) appears quite radiogenic, in the range of -3.4 to -5.2 ɛ-units, about 2 to 4 ɛ-units higher than the detrital fraction. Changes in the ɛ Nd(t) of detrital material delivered to the Zagros Basin appear to control the ɛ Nd(t) of the local bottom waters from the Coniacian to the middle Campanian. By contrast, decoupling of detrital ɛ Nd(t) from that of the local bottom waters from the middle Campanian to the Maastrichtian points to increasing fluxes of westward flowing Pacific radiogenic water masses into the eastern Tethys at that time. These results support an intensification of the Tethyan Circumglobal Current, likely related to the narrowing of the Tethyan seaway. • Alternating humid and arid periods throughout the Late Cretaceous of Zagros. • Ophiolite sequence was aerially exposed as soon as the Coniacian in the Zagros area. • Intensification of the TCC from the middle Campanian to the Maastrichtian. [ABSTRACT FROM AUTHOR]

The recovery time of marine productivity following the Cretaceous-Paleogene (KPg) mass extinction varies tremendously with location (hundreds to millions of years), with possible delays in the tropics as compared to higher latitudes. This heterogeneity is based on prevalent oligo- to mesotrophic marine environments. While highly productive eutrophic environments are less prevalent, they play a greater role in the carbon cycle. Here we present data from a eutrophic region within the tropical southern Tethys. Records of both organic matter and calcite production in this locality exhibit stability across the KPg boundary. In addition, our study points to a remarkably rapid recovery (<11 kyr), even possibly continuous high productivity across the KPg boundary, despite the tropical location. Moreover, the characteristic KPg δ13C negative excursion is observed in our locality, but is independent of high productivity, possibly indicating a reduction in the δ13C of the DIC of the ocean due to the input of light carbon from the atmosphere. Thus, this study provides new insight into the functioning of eutrophic ecosystems during environmental stress imposed by the ecological crisis. • A complete stratigraphic section for the Cretaceous-Paleogene (KPg) boundary is described in a eutrophic ecosystem. • Primary and export productivity seems to be continuous or very rapid (<11 ky) recovered following the KPg mass extinction. • δ13C excursion is independent of productivity, suggesting additional light carbon source to the ocean, possibly volcanism. [ABSTRACT FROM AUTHOR]

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]