Displays

The close temporal correlation between the emplacement of large igneous provinces and environmental crises in the geological record suggests a causal relationship. One such example is the emplacement of the North Atlantic Igneous Province (NAIP) and the Paleocene-Eocene Thermal Maximum (PETM), an extreme climate change event that occurred ~56 Ma. The main pulse of activity from the NAIP is around this time, but current radioisotopic ages are too low-resolution to constrain whether this activity was before, during and/or after the PETM. An ideal locality for understanding the initiation and development of the PETM is the island of Fur, northwest Denmark. The sedimentary sequence consists of clays and diatomites deposited in an epicontinental, shallow marine sea. The high sedimentation rates and close proximity to the NAIP means there are numerous volcanic and climatic proxies in the strata that can be used to provide high-resolution records constraining the relative and absolute timings of these events.

Here we present the findings of the project ‘Ashlantic’, which focuses on pre- to post-PETM strata. We adopt a multiproxy approach using volcanic tracers, including tephra horizons, Hg anomalies, and Os isotopes, to infer the intensity and timing of NAIP activity. Volcanic glass morphology and chemistry suggests a hydromagmatic origin for key tephra intervals, while U-Pb dating of magmatic zircon constrains the timing of NAIP activity and the development of the PETM. Detailed chemostratigraphic logs and datasets (e.g. δ¹³C analyses) define the onset and duration of the PETM, while clay chemistry, Li isotopes, total organic carbon (TOC), and the paleothermometer TEX₈₆ are used to assess the climate response to global warming during the PETM. In concert, our results suggest that the NAIP was active just before, during, and after the PETM, but the relationship between the NAIP and the marine and terrestrial environments is complex. These findings call for further work, such as ICDP and/or IODP drilling of North Sea sediments.

How to cite: Jones, M., Stokke, E., Augland, L., Pogge von Strandmann, P., Liu, E., Mather, T., Rooney, A., Tierney, J., Whiteside, J., Tegner, C., Schultz, B., Planke, S., and Svensen, H.: Constraining North Atlantic Igneous Province (NAIP) activity during the late Paleocene and early Eocene, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6727, https://doi.org/10.5194/egusphere-egu2020-6727, 2020.

Among the "big five" mass-extinction events during the Phanerozoic, the end-Cretaceous extinction 66 million years ago is particularly well known because it marks the demise of the non-avian dinosaurs. Evidence for the Chicxulub impact as the primary cause of this mass extinction has been accumulating over the past four decades, but there are still many open questions regarding the detailed course of events.

Building on our earlier modelling results demonstrating strong global cooling due to sulfate aerosols formed in the wake of the Chicxulub impact (Brugger, Feulner & Petri 2017, Geophys. Res. Lett., 44:419-427), we here explore the response of the ocean in more detail. Specifically, we added a marine biogeochemistry module to a coupled atmosphere-ocean model to investigate the effects of the impact on ocean geochemistry and primary productivity.

We find that the formation of stratospheric sulfate aerosols leads to a marked decrease in annual global mean surface air temperatures by at least 26°C in the coldest year after the impact, returning to pre-impact temperatures after about one century. The strong surface cooling induces vigorous ocean mixing that leads to changes in oxygen distributions and nutrient availability. Due to the darkness, marine net primary productivity essentially shuts down in the first years after the impact. Once the light returns, however, we find a significant increase in primary productivity caused by a surge in nutrient availability, both due to upwelling in the ocean and delivery by the impactor. These strong perturbations of the marine biosphere further support the notion that the impact played a decisive role in the end-Cretaceous mass extinction.

How to cite: Feulner, G., Brugger, J., Hofmann, M., and Petri, S.: Severe perturbations of the marine biosphere following the Chicxulub impact, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8025, https://doi.org/10.5194/egusphere-egu2020-8025, 2020.

The Cretaceous–Paleogene boundary (KTB or KPB) mass extinction is primarily known for the
demise of the dinosaurs, the Chicxulub impact, and the rancorous forty-year-old controversy
over the cause of this mass extinction. For the first 30 years, the controversy primarily revolved
around the age of the impact claimed as precisely KTB based on the assumption that it caused
the mass extinction. The iridium (Ir) anomaly at the KTB was claimed proof of the asteroid
impact, but no Ir was ever associated with impact evidence and recent findings reveal no
extraterrestrial component in PGEs or the KTB Ir anomaly. Impact melt rock glass spherules are
also claimed as indisputable evidence of the KTB age impact, but such spherule layers are
commonly reworked from the primary (oldest) layer in late Maastrichtian, KTB and Danian
sediments; thus only the oldest impact spherule layer documented near the base of zone CF1
~200 ky below the KTB can approximate the impact’s age. Similarly, the impact breccia in the
Chicxulub impact crater predates the KTB. The best age derived from Ar/Ar dating of impact
glass spherules is within 200 ky of the KTB and thus no evidence for the KTB age. All evidence
strongly suggests the Chicxulub impact most likely predates the mass extinction ~ 200 ky and
played no role in it.
Deccan volcanism (LIP) was dismissed as potential cause or even contributor to the KTB mass
extinction despite the fact that all other mass extinctions are associated with Large Igneous
Province (LIP) volcanism but none with an asteroid impact. During the last decade, Deccan
volcanism gained credence based on a succession of discoveries: 1) the mass extinction in
between the longest Deccan lava flows across India; 2) high-precision dating of the entire
sequence of Deccan volcanism based on UPb zircon dating; 3) recognition of four distinct
eruption pulses all related to global climate warming with the largest pulse beginning 20 ky prior
to and ending at the KTB; 4) Identifying the climate link to Deccan volcanism based on age
dating and mercury from Deccan eruptions in marine sediments; and 5) Identifying the KTB
mass extinction directly related to the major Deccan eruption pulse, hyperthermal warming and
ocean acidification all linked to global mercury fallout from Deccan eruptions in marine
sediments. Despite this remarkable culmination of evidence, the controversy continues with
impact proponents arguing that Deccan volcanism didn’t exist at the KTB – the impact was the
sole cause.

How to cite: Keller, G.: Deccan Volcanism or the Chicxulub Impact: The Chicken or Egg Question, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22414, https://doi.org/10.5194/egusphere-egu2020-22414, 2020.

Large Igneous Province (LIP) activity is hypothesized to impact global volatile cycles causing climate changes and environmental crises deleterious to the biosphere. Recent work suggests that the potential of LIPs to impact climate is magnified where they intrude organic-rich (i.e. shale-bearing) sedimentary basins. However, the chemical and degassing dynamics of magma-shale interaction are not well understood. Here we present the first experimental simulations of disequilibrium interaction between LIP magma and carbonaceous shale during upper crustal sill intrusions in the Canadian High Arctic LIP (HALIP), the latter of which were co-eval with oceanic anoxic event 1a. Experiments show that magma-shale interaction results in intense syn-magmatic degassing and simultaneous precipitation of sulfide droplets at the ablation interface. Magma-shale interaction on a basin-scale can thus generate substantial amounts of climate-active H-C-S volatiles, while the presence of strongly reducing volatiles may also increase the likelihood of magma to segregate a sulfide melt. These findings have fundamental consequences for our understanding of both large-scale Earth outgassing and metal prospectivity in sediment-hosted LIPs.

How to cite: Deegan, F., Bédard, J., Troll, V., Dewing, K., Geiger, H., Grasby, S., Misiti, V., and Freda, C.: Voluminous crustal degassing and immiscible sulfide genesis caused by magma-shale interaction in Large Igneous Provinces, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-14578, https://doi.org/10.5194/egusphere-egu2020-14578, 2020.

The connection between volcanic activity of large igneous provinces and the respective feedback from environment and biosphere contributing to the carbon cycle has been investigated at the present temporal resolution of high-precision U/Pb dating. Uncertainties of 0.05 % on the ²⁰⁶Pb/²³⁸U age from zircon dating allow a resolution of 30-50 ka pulses of magmatic activity; simultaneously, the duration of carbon isotope excursions (CIE) can be determined, the geological boundaries dated, or global sedimentary gaps can be quantified at the same level of precision. This contribution demonstrates with two case studies that we can refine the contemporaneity and start to reliably infer causality of consecutive events at the 10⁴ year level.

Until the Anisian the aftermath of the Permo-Triassic Boundary Mass extinction (PTBME; ~251.94 Ma, Baresel et al., 2017) is characterized by profound fluctuations of the global carbon cycle with amplitudes of up to 8 ‰ in d¹³C_carb values. These represent large variations in the global climate and biological crises, in particular during the end-Smithian extinction event (~249.1 Ma). A precise chronology from the southern Nanpanjiang basin (China) allows for a quantification of these fluctuations of Earth climate. Following the volcanic pulse causing the PTBME, several discontinuous episodes of volcanism of the Siberian Large Igneous Province (S-LIP) were generally assumed to have caused the subsequent Early Triassic carbon cycle fluctuations. This is, however, in disagreement with the geochronological database of precise zircon U/Pb dates that put an end to the volcanic activity at 250.6 Ma (Burgess & Bowring, 2015; Augland et al., 2019). Therefore, recurrent S-LIP volcanism is an unlikely explanation for the Early Triassic unstable carbon cycle.

The initial intrusive pulse of the Karoo Large Igneous Province (K-LIP) formed the sill/dyke complex of the Karoo basin, South Africa. New, precise U/Pb geochronology confirms its very short duration at around 183.2-182.8 Ma (Burgess et al., 2015; Corfu et al., 2016), as well as its synchronicity with the lower Toarcian oceanic anoxic event (T-OAE), and a carbon cycle disturbance of presumable global importance. Repeated excursions in d¹³C_org of up to 3 ‰ in the late Pliensbachian (~185.5 Ma) as well as at the Pliensbachian-Toarcian boundary (~183.5 Ma) are therefore at least partly older than any known magmatic activity of the K-LIP (Lena et al., 2019). We therefore, again, must invoke non-volcanic drivers in order to explain the instability of the carbon cycle.

These two case histories demonstrate that in order to invoke causality and global importance to carbon cycle instability, as well as for the testing of its correlation with volcanic episodes, we need to rely on geochronology of both sedimentary and volcanic records at the 10⁴ years level of precision.

References: Augland et al. (2019) Scientific Reports, 9:18723 ; Baresel et al. (2017) Solid Earth, 8, 361–378, 2017; Burgess & Bowring (2015) Science Advances, 1(7), e1500470–e1500470; Burgess et al. (2015) Earth and Planetary Science Letters, 415(C), 90–99; Corfu, F. et al. (2016) Earth and Planetary Science Letters, 434(C), 349–352; Lena et al. (2019) Scientific Reports, 9:18430.

How to cite: Schaltegger, U., Widmann, P., Greber, N. D., Lena, L., Gaynor, S. P., Vennemann, T., and Bucher, H.: Refining the temporal relation between Large Igneous Provinces and carbon cycle perturbations: not every LIP triggers environmental crises, not every crisis is due to a LIP!, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2141, https://doi.org/10.5194/egusphere-egu2020-2141, 2020.

Eruptions of Large Igneous Provinces (LIP) are commonly correlated with global climate change, and environmental, as well as biological, crises. However, establishing a causative link via chemical and physical proxies for global change is more complicated and often ambiguous. As technical improvements have allowed for increasingly higher precision dates especially in U/Pb dating, it is possible to better assess hypotheses connecting LIP’s and environmental impact via their contemporaneity. Here, we focus on the early Jurassic period, which includes a period of global change known as the Toarcian oceanic anoxic event (TOAE), as well as emplacement of the Karoo Large Igneous Province (K-LIP). Previous work has tied these two events together due to overlapping chronology and observed metamorphism and degassing (e.g., Svensen et al., 2012; Sell et al., 2014), and excellent exposure allows for extensive sampling of both the intrusive and extrusive components of the K-LIP. Therefore it is possible to directly study the influence of intrusive LIP magmatism on potential climate forcing.

The K-LIP is comprised of a suite of basaltic lava flows, sills, dike swarms, centered in southern Africa. Approximately 340,000 km³ of sills are interlaid within the Karoo Basin, and therefore served as significant heat source to the basin upon emplacement. While much of the sedimentary rocks of the basin are siliciclastic, the Ecca Group contains organic-rich facies and hosts 160,000 km³ of basaltic sills (Svensen et al., 2012). This unit is therefore uniquely capable of generating large volumes of thermogenic gas through thermal metamorphism of the organic matter of the shale. Previous mass balance calculations indicate that between 7,000 and 27,000 Gt of CO₂ equivalents was released through metamorphic reactions in contact aureoles within the Ecca Group (Svensen et al. 2007). If intrusive magmatism was short lived within this formation, causing rapid volatilization and degassing from the shales, than this event could represent a mechanism to drive a short pulse of global climate change. Previous studies have shown that intrusions are coeval with the TOAE (Svensen et al., 2012; Corfu et al. 2016), however higher-precision geochronology data from the sills is necessary to determine if the flux and timing of thermogenic gases from the basin was sufficiently high to destabilize Earth’s climate. In order to test the hypothesis, we present single crystal U-Pb zircon dates from sills across the Ecca Group. These data will be used (i) to quantify the duration and flux rate of carbon gas during the intrusive event, and (ii) to better understand how and to what extent K-LIP intrusive activity and associated thermogenic gas release of Ecca wall rocks were able to drive global climate change.

Corfu, F., et al., (2016) EPSL, 434, 349-352.

Sell, B., et al., (2014) EPSL, 408, 48-56.

Svensen, H., et al., (2007) EPSL, 3-4, 554-566.

Svensen, H., et al., (2012) EPSL, 325-326, 1–9.

How to cite: Gaynor, S. P., Schaltegger, U., and Svensen, H.: Sills Sautéing Shales: Did Karoo Intrusions into the Ecca Formation cause the Toarcian Ocean Anoxic Event?, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4145, https://doi.org/10.5194/egusphere-egu2020-4145, 2020.

The coincidence between mass extinction events and the emplacement of Large Igneous Provinces (LIPs) in the Phanerozoic geological record points to the magmatic CO₂ degassing as the potential trigger of rapid global-scale climatic and environmental changes. The Central Atlantic Magmatic Province (CAMP) is one of the Earth’s hugest LIPs, and is coincident with the end-Triassic extinction, at ca. 201.5 Ma. Such LIPs emplacement and associated magmatic CO₂ degassing have traditionally been interpreted as occurring over periods much longer than those of anthropogenic CO₂ emissions, however our improving understanding of LIPs activity is reducing these timescales, with the latest estimates indicating CAMP magmatic pulses lasting approximately a few centuries each and characterized by high eruption rates [1; 2]. We employed a biogeochemical model to investigate the effects on ocean-atmosphere system and climate of these CAMP magmatic pulses, and to test whether such rapid and intense magmatic CO₂ degassing is consistent with the climatic, geochemical and palaeontological record of the end-Triassic. Hence, we compared the modern anthropogenic emissions (since the Industrial Revolution) with the pulsed magmatic degassing during CAMP emplacement, in order to evaluate the impact of rapid and intense events on climate and environment changes.

[1] Knight et al. (2004), Earth Planet. Sci. Lett. 228, 143-160. [2] Marzoli et al. (2019), J. Petrol. 60, 945-996.

How to cite: Capriolo, M., Mills, B., Newton, R., Dal Corso, J., Dunhill, A., and Marzoli, A.: Rapid and intense CO2 emissions into the atmosphere: Examples from the end-Triassic extinction, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10473, https://doi.org/10.5194/egusphere-egu2020-10473, 2020.

The Palaeogene represents the last “greenhouse” period characterized by high atmospheric CO₂ concentrations and warm surface temperatures. This long-term climatic state was punctuated by several transient hyperthermal events. These events are recorded primarily by prominent negative carbon isotope excursions (NCIE) in both carbonates and organic matter of sedimentary successions. The largest hyperthermal of the Palaeogene, the Palaeocene-Eocene Thermal Maximum (PETM), is associated with a 5-8° rise in global temperature, ocean acidification and a global biotic perturbation. The PETM is thus often seen as a geological analogue for future greenhouse-gas-driven global warming. The source of the ¹³C-depleted carbon for the NCIE and whether it was released in one or numerous events however remains controversial. Numerous carbon sources have been suggested, either in concert or individually to explain the onset and the duration of the NCIE. These include magmatic as well as thermogenic release of CO₂ associated with large scale magmatism. Over the last decade, mercury (Hg) found in marine and continental sedimentary succession has emerged as a potential proxy of past volcanic emissions, allowing to trace the relationship between the emplacement of Large Igneous Provinces (LIP) and periods of warming, mass extinctions, and biotic disruptions.

Although the PETM is widely recorded in pelagic and hemipelagic settings, its record in shallow-water and continental successions remains scarce due to frequent hiatuses and unconformities in such environments and a lack of enough biostratigraphic constraints. However, the high sedimentation rate, which may characterize shallow water settings, compared to deeper marine environments, may potentially preserve expanded NCIE successions to better understand the nature and causes of the PETM

In this study, we present the first synthetic high-resolution mercury and stable isotopic records of three shallow-water and continental successions from highly subsident peripheral basins North (Lussagnet) and South (Serraduy and Esplugrafreda) of the Pyrenean orogen across the PETM. In those sections, our results show two important negative carbon isotope excursions in the bulk-rock carbonates. Based on biostratigraphy and similarity of shape and amplitude of the isotopic excursions with global records, the largest NCIE is interpreted as the NCIE associated with the PETM. This excursion is immediately preceded by another NCIE, second largest in amplitude in our record, and that we interpret as the Pre-Onset Excursion (POE), found in few other profiles worldwide. The occurrence of the POE suggests a first episode of ¹³C-depleted carbon release before the onset of the PETM. These various NCIE are associated with important mercury anomalies, even when normalized to total organic content. This suggests that pulses of magmatism, probably associated to the emplacement of the North Atlantic Igneous Province (NAIP), contributed to the onset and to the long duration of the PETM.

Our work confirms that hyperthermal events of the Palaeogene can be well recorded in shallow water and continental successions and can be used as powerful stratigraphic tools for these depositional environments, in addition to providing information on the climatic perturbations associated with the PETM.

This work is founded and carried out in the framework of the BRGM-TOTAL project Source-to-Sink.

How to cite: Tremblin, M., Khozyem, H., Spangenberg, J. E., Fillon, C., Lasseur, E., Serrano, O., Roig, J.-Y., Calassou, S., Guillocheau, F., Adatte, T., and Castelltort, S.: Mercury anomalies in Palaeocene-Eocene Thermal Maximum (PETM) successions of Pyrenean peripheral basins: new evidence of a plausible link between volcanic emissions from the North Atlantic large igneous province and the PETM, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9792, https://doi.org/10.5194/egusphere-egu2020-9792, 2020.

The Cretaceous-Paleogene boundary (K-PgB) interval of Denmark has been the subject of numerous contributions for understanding this mass extinction, focusing essentially on the famous coastal exposures of Stevns Klint (Sjælland). Although less popular, exposures of the K-PgB are also known in northern Jutland (NW Denmark) and have been the subject of a few contributions on their macro- and microfaunal content. Through an integrated study of the section of Nye Kløv (biostratigraphy and high-resolution stable isotope stratigraphy), we show here that the KPgB interval in northern Jutland presents the double advantage of (1) being continuous across the latest Maastrichtian to early Paleogene (contrary to Stevns Klint sections that bear several discontinuities such as prominent hardgrounds) and (2) bearing well-preserved macro- and microfossil assemblages, and isotopic trends in carbon and oxygen. Bulk carbonate oxygen isotopes delineate with great precision temperatures trends across the KPgB interval with cyclic oscillations that faithfully reproduce trends of the La2010b astronomical solution, hence allowing for an astronomical calibration of the section. The orbital calibration of the KPgB in Nye Kløv points to an age of 66.01 Ma. Our study delineates a Deccan warming optimum at 66.25 Ma corresponding to the deposition of the Kjølby Gaard marl, a distinct marly layer that can be traced throughout the North Sea. A clear shift toward the end-Maastrichtian cooling follows the Deccan warming at 66.1 Ma and precedes a last pulse of warming immediately below the boundary at 66.02 Ma. The earliest Danian is characterized by lower temperatures up until 65.88 Ma, after which temperatures resume to the same range as those of the Deccan warming, albeit with strong oscillations that reflect pacing by the short-eccentricity. This shift toward much warmer temperatures is associated with a first negative excursion in carbon isotopes. A second marked negative excursion in carbon isotopes occurs at 65.65 Ma and taken all-together, the overall warm interval comprising these two carbon isotope excursions reflects the local expression of the Dan-C2 hyperthermal event. Orbital calibration of the Nye Kløv section also allowed us to determine the timing of the recovery in the benthic community in the Boreal Chalk Sea, marked by an increase in skeletal fragments and brachiopod diversity, which occurred at 65.8 Ma, hence in conjunction with the Dan-C2 event.

How to cite: Møller, S. D., Adatte, T., Bjerrum, C. J., and Thibault, N.: Timing environmental perturbations across the Cretaceous – Paleogene boundary in the Boreal Realm (N. Denmark), EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19252, https://doi.org/10.5194/egusphere-egu2020-19252, 2020.

If most experts agree that the Cretaceous-Paleogene (K-Pg) extinction (66 Ma) resulted from a combination of the Chicxulub impact and of Deccan volcanism, the chain of reactions (Bond and Wignall, 2014) leading to the extinction is not well constrained. 
 
 In the present study, we use the GEOCLIM model to explore extreme perturbations induced by the two events and to investigate processes leading to the marine extinction. This state-of-the-art numerical tool (geoclimmodel.wordpress.com) includes in particular a marine ecological model in which food webs are simulated and marine organisms are sensitive to abiotic factors of their environment. The characteristics of each “species” of marine organisms, such as the tolerance to pH or temperature changes or the efficiency of predation, are randomly fixed to avoid any determinism in the response to the environmental perturbations. 

  The response of the Earth system to the onset of Deccan traps and to the Chicxulub impact is explored by forcing the model with the most recent “eruptive sequences”  (Schoene et al., 2019, Sprain et al. 2019) and with the assumption of a pulse-like degassing (Chenet et al. 2009) sequence over 500 kyrs that includes CO2 and SO2. This new approach allows us to take into account the interplays between the sulfur and carbon cycles on multiple time scales (from year to 105  yrs) and to capture the model sensitivity to the uncertainties in atmospheric emissions (duration, timing, nature of gases, intensity of pulses, intensity of the impact).

  The coupled evolution of the Earth’s climate and oceanic geochemistry during the K-Pg boundary crisis will be presented. Without considering evolution processes, the biotic response (biomass and biodiversity) will be discussed with respect to the ecosystem structure existing before the perturbations. 

How to cite: Guillaume, L. H., fréderic, F., Salome, H., and Yves, G.: New insights about the processes leading to marine extinction at the K-Pg boundary using a coupled biogeochemical-ecosystem model, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20315, https://doi.org/10.5194/egusphere-egu2020-20315, 2020.

Recent multi-disciplinary efforts demonstrate a correlation between continental flood basalt (CFB) volcanism and major environmental catastrophes associated with four out of the five largest Phanerozoic mass extinctions. Unique among these is the end-Cretaceous mass extinction, which is potentially coincident with both the Chicxulub bolide impact and the Deccan volcanism. Among these two drivers, the role of the Deccan volcanism is crucial in order to decipher if there is a causal relationship between volcanism and environmental stress, and if so, how stressed the environment was during the latest Maastrichtian. To assess the cause-and-effect relationship between Deccan volcanism and climate change and mass extinctions, high-resolution biostratigraphy, quantitative species analysis coupled with geochemical measurements have been performed on complete sections of Mudurnu-Göynük and Haymana basins (Turkey).

In both basins Maastrichtian sedimentation is characterized by monotonous mudstones, which sharply in turn to marl-calcareous mudstone alternations in the earliest Danian. Detailed quantitative study on planktonic foraminifera of the Haymana Basin revealed that planktonic foraminiferal community in the latest Maastrichtian is dominated by ecological generalists with small, simple morphologies (e.g., Heterohelix, Globigerinelloides, Guembelitria). Among them low oxygen tolerant Heterohelix globulosa is the most dominant taxa and their abundance changing with the presence of stress marker Guembelitria cretacea. In all sections, the K/Pg boundary itself is characterized by 2-3 mm thick reddish oxidized layer which corresponds to sudden annihilation of large, ornamented ecological specialists (e.g., Globotruncana, Rugoglobigerina, Racemiguembelina). Right after the boundary, there is an acme of calcareous dinoflagellate cysts (Thoracosphaera) and a surge of Guembelitria cretacea indicate ecosystem collapse in post-K/Pg environment.

On the other hand, detailed quantitative analysis shows a systematic reduction in the species richness throughout the Plummerita hantkeninoides Zone corresponding to the final 150 kyr of the Cretaceous. Proliferations of the Guembelitria cretacea through late Maastrichtian is known as an indicator of high terrigenous influx; therefore, enhanced food resources. The high sedimentation rates observed in all the studied sections might be linked to increased greenhouse conditions due to Deccan volcanism leading to enhanced weathering. Overall, our multiproxy approach including quantitative biostratigraphy and geochemical analyses highlights the influence of the Deccan volcanism by releasing high amounts of atmospheric CO₂ and SO₂, leading to the climatic changes and associated biotic stress, which predisposed faunas to eventual extinction at the K/Pg boundary.

How to cite: Karabeyoglu, A. U., Adatte, T., Lorenzo, V., Spangenberg, J., Özkan Altıner, S., and Altıner, D.: Faunal and environmental changes through the Cretaceous-Paleogene boundary (K-Pg) linked with Deccan Volcanism: evidence from the Neo-Tethys, Turkey, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2002, https://doi.org/10.5194/egusphere-egu2020-2002, 2020.

Major events like global anoxic episodes and mass extinctions are often associated with the eruption of Large Igneous Provinces (LIPs) in the geological past. The Deccan Trap eruption in the end-Cretaceous period in India forms the second-largest LIP and has often been causally linked to the Cretaceous-Paleogene Boundary (K/PgB) mass extinction event. To date, however, environmental reconstructions from pre- and post-volcanic sequences (infra- and inter-trappean, respectively) have mostly been qualitative and fragmentary and as a result, the effects of volcanism on the adjacent environmental conditions are still not well understood. Here, we present evidence of bottom water anoxia as a direct consequence of the Deccan volcanism. For this work, we analyzed major and trace element abundance, total organic carbon (TOC), bulk carbon isotope composition (δ¹³C_org), and molecular characterization of organic matter (OM) from shallow marine trappean sediments in Rajahmundry, SE India, where the main volcanic episodes separating the infra- and inter-trappean sediments also encompass the K/PgB. The infra-trappean shows overall low TOC (<0.1%) and δ¹³C_org (–26.3±0.4‰) values, with relatively higher concentrations of longer-chained n-alkane homologues and detrital elements (Al, Ti, Th, K) suggesting a larger contribution from terrestrial derived OM. Across volcanism, however, there is considerable decrease in terrigenous influx, as well as lowering in Pristane/Phytane ratios (<0.6) and enrichment in redox-sensitive elements like Mo, U, V and Co. This is also accompanied by contemporaneous increases in TOC (~0.6%) and δ¹³C_org values (~3.9‰), suggesting that the change from oxic to sub-oxic or anoxic condition after the main volcanic episode led to increased OM burial and perturbations in the shallow marine carbon reservoir. Higher supply of micro-nutrient during this interval, as evidenced from enrichment in Ba, Fe, Ni and Zn possibly suggest that hydrothermal recycling and initial phases of eutrophication led to depletion in the bottom-water oxygen levels. Temperature increases due to CO₂ degassing from volcanism may have further decreased the solubility of oxygen in the sea-waters; however, further studies from the volcanic province are required to ascertain the underlying causes and extent of perturbations and ultimately, to better constrain the complex environmental feedbacks associated with the Deccan volcanism.

How to cite: Roy, S. and Sanyal, P.: Anoxic bottom water condition during the Deccan volcanism: Multi-proxy evidences from a shallow marine sequence in Rajahmundry, SE India, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1037, https://doi.org/10.5194/egusphere-egu2020-1037, 2020.

Recent studies indicate that the bulk (80%) of Deccan trap eruptions occurred over a relatively short time interval in magnetic polarity C29r. U-Pb zircon geochronology shows that the main phase began 250 ky before the Cretaceous-Paleogene (KPg) mass extinction and continued into the early Danian suggesting a cause-and-effect relationship. But the potential causal relationship between paleo-environmental change and Deccan volcanism remains debated. New U-Pb zircon geochronology from the Malwa Plateau (~7% of the inferred total volume of the Deccan LIP) located on the northern margin of the Deccan Traps allows  to correlate basalts from the periphery of the province with the volcanic stratigraphy of the Western Ghats as well as to global paleoenvironmental records and precise the Deccan eruption rates at larger scale. Main part of the basalts released in northern Deccan area appears to be of latest Maestrichtian age.  Moreover recent geophysical and field observations show that the Malwa and Mandla basalt plateaus erupted in the Narmada-Tapti rift, made up of 2-3.5 km of Carboniferous to Cretaceous sedimentary rocks, including  up to 60m thick Lower Permian coal interval. Numerous dolerite dykes and sills intersecting these coal beds have been observed in open and underground mines from the Satpura area. The interaction between these dykes  and the coal seams may have significantly contributed to the latest Maastrichtian warming  by releasing high amounts of CO2, SO2 and halogens into the atmosphere. These observations indicate that Deccan volcanism played a key role in increasing atmospheric CO2 levels that resulted in global warming and enhanced greenhouse effect during the latest Maastritchtian, which coupled with high SO2 emissions, increased biotic stress and predisposed faunas to eventual extinction at the KTB.

How to cite: Adatte, T., Eddy, M., Schoene, B., Keller, G., and Khadri, S.: Late Maastrichtian global warming triggered by Deccan dykes and sills, evidence from Malwa and Mandla regions, Central India., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4201, https://doi.org/10.5194/egusphere-egu2020-4201, 2020.

The Toarcian Ocean Anoxic Event (TOAE) took place in the early Jurassic (­ ∼183 My) and is characterised by the widespread deposition of organic matter-rich black shales in deep basins, and by a negative carbon isotope excursion reflecting profound environmental changes. This event is well documented in the sedimentary record of deeper marine settings, in which the TOAE is marked by the presence of organic-rich shales. However, the recording of the TOAE in shallower environments is less common, due to incomplete sediment records, to sea-level fluctuations and the lack of good biostratigraphy markers.

Here we present data gathered from a new extremely shallow section in Morocco (Dadès Gorges, Central Atlas), which was located along the northern Gondwana margin. This section consists of alternating dolomitic limestones and paleosols, associated with the presence of several dinosaur tracks and other sedimentary features such as stromatolites, ripple marks, mud cracks and fossil roots. This section shows a significant increase in mercury (Hg) located just below a negative excursion in ¹³C _carbonate isotopes (-3 ) that we attributed to the TOAE NCIE, which coincides with several cyclical episodes of emersion. Bulk rock and clay mineralogy indicate an increase in weathering intensity in the upper part of the section marked by higher phyllosilicates quartz and kaolinite contents.

The upper part of the section shows a gradual decrease in the number of carbonate banks coinciding with an increase of clay-rich intervals. The carbonate banks interbedded with the clay levels are almost entirely composed of an accumulation of stromatolites reflecting even more extreme conditions, which coincide with the TOA-NCIE.

These results confirm the presence of the TOAE-NCIE even in the most shallow environments of the Tethys. The observed Hg anomalies have been globally recorded and are probably linked with the volcanic activity from the Karoo Ferrar province. This marker combined with stable isotopes is therefore a very promising correlative tool.

How to cite: Ruchat, A., Adatte, T., and Spangenberg, J.: Toarcian Ocean Anoxic Event (TOAE) recording in shallow environment : example from Central Atlas, Morocco, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18005, https://doi.org/10.5194/egusphere-egu2020-18005, 2020.

The end-Triassic extinction event just below the Triassic/Jurassic boundary and its dramatic paleoenvironmental and paleogeographical variations are well documented by rapid changes in the sedimentological and geochemical composition of the uppermost Triassic and lowest Jurassic sequence in the NE Paris Basin. 

An outstanding horizon in the Middle Rhaetian of the Paris Basin is the result of the effects generated by the asteroid impact of Rochechouart (~50 km large crater, ~201 Ma old). The asteroid hit the variscan basement at the southern margin of the Paris Basin, near the town of Limoges (France). This horizon starts at its base with seismically deformed alternation of siltstones and quartzites (seismite), which represent the result of a mega earthquake, generated during the initial impact phase. The seismite is overlain by a completely unsorted conglomerate, fining upwards into a strongly folded and sheared silt/clay with numerous vertebrate bones and ends at the top with a thick red clay formation of the Upper Rhaetian.

The horizon above the seismite obviously represents the deposits of a large tsunami (called tsunamite), triggered when the enormous ejecta masses of the impact entered the waterbody of the southern Paris Basin. Indicators for this event are not only the remains of the reworked vertebrates and exotic sedimentological structures. Additionally the enrichment of platinum group elements which was found in the sequence, clearly points to an impact with cosmic material being involved. The layer can be observed from the Eifel (Germany) over Luxembourg to Lorraine (France). Thickness, sedimentological structures and the lithological composition differ locally, mainly depending on the former geomorphological situation.

Here we present similar impact horizons in two other sites from France: in the northern Aquitanian Basin near Brive-la-Gaillarde (which is in a close distance to the crater) and in the southern Lodève Basin (at a larger distance and in carbonatic rocks). Intensive research in these areas is still in progress.  

The excellently conserved Rochechouart impactite in the Rhaetian of the Paris Basin and surrounding regions offers a unique chance to study in all detail the processes of a large impact with their effects on the adjacent marine sedimentation areas and to compare the results to similar events  worldwide.

How to cite: Kuhlmann, N., Thein, J., Nagel, T., and Colbach, R.: Traces of the Rochechouart Asteroid Impact in the uppermost Triassic sediments of the NE Paris-, Aquitanian- and Lodève Basin , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8692, https://doi.org/10.5194/egusphere-egu2020-8692, 2020.

Hyaloclastites have long been described within numerous volcaniclastic sequences in the Siberian Traps Large Igneous Province. They are typical for the southern and central parts of the Tunguska basin, and we inspected them in 2004-2010. In recent years, we have focused our attention on the northwestern region of the Tunguska basin (Norilsk area) with a volumetric manifestation of basaltic lava flows. We have completed fieldwork in this region from 2006 to 2019, with a recent focus on the understanding of the emplacement environments for the lowermost lava flow erupted directly on the end-Permian boggy surface. We studied pillow basalt at the basal part of the lowermost lava flow in the Norilsk region (Ivakinskaya Formation). In the upper part of this pillow basalt horizon, hyaloclastite is very common, and at the basal part, several tree trunks occur. The hyaloclastite includes black equant angular clasts and rusty red matrix and easily recognize at any outcrops. We studied hyaloclastite with optical microscopy and SEM-EDS. Black clasts composed of sideromelane cracked and altered to palagonite. Sideromelane fragments include crystals of olivine (Fo70), plagioclase (An63-70), and likely OPx altered to chlorite. Sideromelane glass has a basalt composition with elevated P2O5, CaO, and decreased amount of MgO and minor halogens (F, Cl). Some sideromelane clasts bear round inclusions (blobs) entirely infill with dolomite, siderite, and calcite. Every single carbonate inclusion has a specific structure and minerals infill.

We interpret these hyaloclastite rocks formations with carbonate inclusions as a result of lava flow effusion onto the shallow freshwater basin or boggy surface. Water and organic-rich sediments transferred with an explosion to steam and carbon dioxide gas, and this gas mixture was formed a hyaloclastite horizon at the basal part of a lava flow. We suppose that these sideromelane clasts with carbonate blobs are additional evidence of greenhouse gas generation during the early stage of the Siberian Traps lavas eruption.

How to cite: Polozov, A. G., Planke, S., Millett, J. A., Zastrozhnov, D. A., Jerram, D. A., and Svensen, H. H.: Hyaloclastite formation during the effusion of the first lava flows of Siberian traps into a shallow freshwater basin, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18885, https://doi.org/10.5194/egusphere-egu2020-18885, 2020.

The end-Permian Siberian Traps large igneous province (LIP) is temporally associated with the major extinction event at the Paleozoic-Mesozoic boundary. The extinction was likely triggered by massive eruption of carbon and halocarbon gases released from metamorphic aureoles around sill complexes in the Tunguska Basin. Additional environmental pollution was likely associated with magma degassing, forest fires, and extensive tuff formation during magma-water interaction. We have conducted detailed field work in the Norilsk area since 2006 to study the environment during the initial lava eruptions in the Siberian Traps. The field work included mapping, photogrammetric drone surveying, sampling, and subsequent inorganic geochemical and petrographic analyzes. The sediment-lava transition is particularly well exposed in the Norilsk area. In the Kajerkan quarry, shallow basaltic igneous intrusions were emplacement into the coal-rich upper part of the Tunguska Group of Late Carboniferous and Permian age. In the Ore Brook and Red Rocks localities, more than ten sub-vertical tree trunks have been mapped and sampled in the lowermost lava flow. The tree trunks are petrified wood of end-Permian age. Pillow basalts are found at the same levels, showing that the lava flow was emplaced in a wet environment. Ropy pahoehoe structures are found at the top of this flow, which suggests that the uppermost part of the lava flow was emplaced in a subaerial environment. Further south, in the Bratsk area, extensive sill intrusions and magnetite-rich hydrothermal vent complexes are abundant, documenting extensive eruptions of metamorphic gases and tuffs to the atmosphere. We have been drilling two 100-m long stratigraphic boreholes across the Permian-Triassic boundary in Svalbard, arctic Norway, to study the effect of the Siberian Traps magmatism on the sedimentary basin development some 2000-km away from the main eruption sites. The near complete core recovery, complemented by material collected in a river section ca. 1 km north-east of the drill site, allowed high-resolution analyses of the Permian-Triassic boundary interval. The cores have been logged and analyzed in detail, including organic and inorganic geochemistry, isotope geochemistry, petrography, and biostratigraphy. The Permian-Triassic boundary (PTB) is identified in the cores and lies within the Reduviasporonites chalastus Assemblage Zone, 2.50 m above the lithological change from bioturbated to dark grey, laminated mudstones. This corresponds to the local position of the Late-Permian Mass Extinction event (LPME) and its associated sharp negative δ¹³C_org excursion. High-resolution environmental proxies indicate a dramatic change in provenance across the PTB, and a transition towards a more arid climate in the earliest Triassic. This transition was contemporaneous with prolonged bottom-water dysoxic or anoxic conditions, following a Late Permian increase in volcanic activity, probably linked to the emplacement of the Siberian Traps LIP. Zircons have been separated from numerous basaltic ash layers in this sequence, and a few have been successfully dated with the U-Pb TIMS method and overlap in age with the Siberian Traps magmatism. This study shows that the Siberian Traps LIP had a major impact of both the basin development and life in the arctic Barents Sea region.

How to cite: Planke, S., Polozov, A., Millett, J., Jerram, D., Zastrozhnov, D., Svensen, H., Augland, L., Jones, M., Zuchuat, V., Sleveland, A., Midtkandal, I., Twitchett, R., and Faleide, J. I.: The Siberian Traps magma emplacement dynamics links to environmental changes across the Permian-Triassic boundary in Svalbard, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21766, https://doi.org/10.5194/egusphere-egu2020-21766, 2020.