The Norian "chaotic carbon interval": New clues from the δ13Corg record of the Lagonegro Basin (southern Italy)

A global carbon-isotope curve for the Late Triassic has the potential for global correlations and new insights on the complex and extreme environmental changes that took place in this time interval. We reconstruct the global δ 13 C org profile for the late Norian, improving on sparse published data from North American successions that depict a "chaotic carbon-isotope interval" with rapid oscillations. In this context, we studied three sections outcropping in the Lagonegro Basin (southern Italy), originally located in the western Tethys. The carbon-isotope profiles show four negative excursions correlatable within the Lagonegro Basin. In particular, a negative shift close to the Norian/Rhaetian boundary (NRB) appears to correlate with that observed in the North American δ 13 C org record, documenting the widespread occurrence of this carbon cycle perturbation. The 87 Sr/ 86 Sr and 187 Os/ 188 Os profiles suggest that this negative shift was possibly caused by emplacement of a large igneous province (LIP). The release of greenhouse gases (CO 2 ) to the atmosphere-ocean system is supported by the 12 C enrichment observed, as well as by the increase of atmospheric p CO 2 inferred by different models for the Norian/Rhaetian interval. The trigger of this strongly perturbed interval could thus be enhanced magmatic activity that could be ascribed to the Angayucham province (Alaska, North America), a large oceanic plateau active ca. 214 ± 7 Ma, which has an estimated volume comparable to the Wrangellia and the Central Atlantic Magmatic Province (CAMP) LIPs. In fact, these three Late Triassic igneous provinces may have caused extreme environmental and climate changes during the Late Triassic

Chemo-Biostratigraphic characterization of the Triassic/Jurassic boundary interval in the Western Southern Alps

The latemost Triassic was marked by a major mass extinction event, following profound global environmental changes likely related to the activity of the Central Atlantic Magmatic Province (CAMP), including: i) rapid sea-level fluctuations, ii) perturbations of the global C cycle, iii) and the collapse of the carbonate biological factory. Several studies tempted to stratigraphically constrain this global event and reconstruct the causative dynamics behind this dramatic extinction. In this work, we investigated the freshly-caved Italcementi active Quarry section, outcropping on the Mt. Albenza (Lombardy Basin, Southern Alps, Italy), for organic and carbonate carbon isotopes and calcareous nannofossils, contributing to the stratigrafic and paleoceanographic characterization of the end- Triassic interval. The new isotopic data highlight the occurrence of three 13C anomalies, which have been demostrated to be of global significance and to correspond to: 1) the late Rhaetian \u201cprecursor Carbon Isotope Excursion (CIE)\u201d; 2) the latemost Rhaetian \u201cinitial negative CIE\u201d; 3) and the Early Jurassic \u201cmain CIE\u201d. These excursions likely correspond to different phases of the CAMP volcanism probably responsible for perturbations in the ocean-atmoshpere system. We identify changes in nannofossil abundance and composition in correspondence of these intervals. In particular, a turnover is detected in correspondence of the \u201cinitial negative CIE\u201d with the first occurrence of Jurassic species coinciding with the end of the 13C anomaly thus being at a lower stratigraphic level than found in other localities worldwide. Further analyses are therefore required to cast light on this new evidence

Chemo-biotratigraphic characterization of the Triassic/Jurassic boundary interval in the Western Southern Alps

The latemost Triassic was marked by a major mass extinction event, following profound global environmental changes likely related to the activity of the Central Atlantic Magmatic Province (CAMP), including: i) rapid sea-level fluctuations, ii) perturbations of the global C cycle, iii) and the collapse of the carbonate biological factory. Several studies tempted to stratigraphically constrain this global event and reconstruct the causative dynamics behind this dramatic extinction. In this work, we investigated the freshly-caved Italcementi active Quarry section, outcropping on the Mt. Albenza (Lombardy Basin, Southern Alps, Italy), for organic and carbonate carbon isotopes and calcareous nannofossils, contributing to the stratigrafic and paleoceanographic characterization of the end- Triassic interval. The new isotopic data highlight the occurrence of three 13C anomalies, which have been demostrated to be of global significance and to correspond to: 1) the late Rhaetian \u201cprecursor Carbon Isotope Excursion (CIE)\u201d; 2) the latemost Rhaetian \u201cinitial negative CIE\u201d; 3) and the Early Jurassic \u201cmain CIE\u201d. These excursions likely correspond to different phases of the CAMP volcanism probably responsible for perturbations in the ocean-atmoshpere system. We identify changes in nannofossil abundance and composition in correspondence of these intervals. In particular, a turnover is detected in correspondence of the \u201cinitial negative CIE\u201d with the first occurrence of Jurassic species coinciding with the end of the 13C anomaly thus being at a lower stratigraphic level than found in other localities worldwide. Further analyses are therefore required to cast light on this new evidence

Magnetostratigraphy, biostratigraphy, and chemostratigraphy of the Pignola-Abriola section: New constraints for the Norian-Rhaetian boundary

A detailed magnetostratigraphic investiga- tion of the Pignola-Abriola section of Norian to Rhaetian age permits the identification of 22 magnetic polarity reversals grouped in 10 magnetozones. We correlate the magneto- stratigraphy of the Pignola-Abriola section with the Newark astrochronological polarity time scale (APTS). In total, 19 correlation options were tested, and only one (option 7) yielded a statistically significant correlation that was consistent with the available infor- mation on the stratigraphic age of the Newark APTS. After some adjustments to minimize erratic variations in sediment accumulation rates, a final correlation (option 7.1) was used to generate an age model of sedimentation for the Pignola-Abriola section. The Pignola- Abriola section has been correlated with Rhaetian sections from the literature, notably the current global boundary stratotype sec- tion and point candidate for the base of the Rhaetian at Steinbergkogel, Austria, where the Norian-Rhaetian boundary is proposed to be placed at a stratigraphic level contain- ing the first appearance datum (FAD) of conodont Misikella posthernsteini, traced on the Newark APTS to ca. 209\u2013210 Ma. Issues regarding the taxonomy of M. posthernsteini, a species characterized by transitional forms with its ancestor Misikella hernsteini, lead us to propose the alternative option of placing the Norian-Rhaetian boundary at a prominent negative \u3b413C spike observed in the Pignola- org Abriola section at meter 44.5, 50 cm below the level containing the FAD of M. posthernsteini sensu stricto and close to the base of radiolarian Proparvicingula moniliformis zone. This level has been magnetostratigraphically cor- related to Newark magnetozone E20r.2r at ca. 205.7 Ma. Assuming an age of ca. 201.3 Ma for the Triassic-Jurassic boundary, the Rhaetian Stage would have a duration of ~4.4 m.y

The Norian/Rhaetian boundary interval at Pignola-Abriola section (southern Apennines, Italy) as a GSSP candidate for the Rhaetian stage: an update

e Pignola-Abriola section (Southern Apennines, Italy) ful lls all the quali cations required by the Subcommission on Triassic Stratigraphy to be proposed as Global Boundary Stratotype Section and Point (GSSP) candidate for the Norian/Rhaetian Boundary (NRB). e Pignola-Abriola section consists of pelagic basinal strata, well exposed and very well preserved with minimal tectonic stress and deformation, outcropping along the SP5 “della Sellata” road in a very accessible location in a protected natural Park, which assures a long-time preservation of the site. e main marker event proposed to de ne the NRB is the First Appearance Datum (FAD) of the conodont Misikella posthernsteini s.s. at level PIG 24 (m 44.9), which in the study section is associated to other events, useful proxies for the identi cation of the base of the Rhaetian: 1) the base of the radiolarian Proparvicingula moniliformis Zone; 2) a strong negative shift of the δ13Corg, which is documented as a global marker. Both the δ13Corg negative shift and the FAD of M. posthernsteini s.s. occur within the magnetozone MPA-5r of Pignola-Abriola at ~205.7 Ma. In this work we discuss M. posthernsteini taxonomy, phylogenesis, and global correlations with other fossil groups and physical events. Furthermore, we update the already existing conodont and radiolarian biostratigraphy with new data, providing better constraint of the age interval determined by the conodont specie

Chaotic Late Triassic Carbon And The Overlooked Extinction At The Norian-Rhaetian Boundary

The latest Triassic was an interval of prolonged biotic extinction culminated by the end-Triassic Extinction, which is associated with a pronounced perturbation of the global carbon cycle that can be connected to extensive volcanism of the Central Atlantic Magmatic Province (CAMP). Earlier chaotic perturbations of the global carbon cycle can also be tied to the onset of declining latest Triassic diversity, which reached its maximum across the Norian-Rhaetian boundary (NRB). These perturbations are global across the Panthalassa Ocean to both sides of the Pangean supercontinent in both the Northern and Southern Hemispheres. The NRB witnessed the severe global extinctions of significant marine fossil groups, such as ammonoids, bivalves, conodonts and radiolarians. The onset of the stepwise Late Triassic extinctions coincided with the NRB carbon perturbation (d13Corg), indicating that the combined climate and environmental changes impacted the global biota. The trigger of this event is attributed to a volcanic event pre-dating the NRB, an alternative source of volcanogenic gas emissions, and/or a meteorite impact

The Late Triassic Extinction at the Norian/Rhaetian boundary: Biotic evidence and geochemical signature

The latest Triassic was an interval of prolonged biotic extinction culminating in the end-Triassic Extinction (ETE). The ETE is now associated with a perturbation of the global carbon cycle just before the end of the Triassic that has been attributed to the extensive volcanism of the Circum-Atlantic Magmatic Province (CAMP). However, we attribute the onset of declining latest Triassic diversity to an older perturbation of the carbon cycle (\u3b413Corg) of global extent at or very close to the Norian/Rhaetian boundary (NRB). The NRB appears to be the culmination of stepwise biotic turnovers that characterize the latest Triassic and includes global extinctions of significant marine and terrestrial fossil groups. These biotic events across the NRB have been largely under-appreciated, yet together with a coeval disturbance of the carbon cycle were pivotal in the history of the Late Triassic. Here, we present new and published \u3b413Corg data from widespread sections (Italy, Greece, ODP, Australia, New Zealand, USA, Canada). These sections document a previously unknown perturbation in the carbon cycle of global extent that spanned the NRB. The disturbance extended across the Panthalassa Ocean to both sides of the Pangaean supercontinent and is recorded in both the Northern and Southern Hemispheres. The onset of stepwise Late Triassic extinctions coincides with carbon perturbation (\u3b413Corg) at the NRB, indicating that a combination of climatic and environmental changes impacted the biota at a global scale. The NRB event may have been triggered either by gas emissions from the eruption of a large igneous province pre-dating the NRB, by a bolide impact of significant size or by some alternative source of greenhouse gas emissions. As yet, it has not been possible to clearly determine which of these trigger scenarios was responsible; the evidence is insufficient to decisively identify the causal mechanism and merits further study