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Location of Triassic-Jurassic boundary sections at Kendlbachgraben (subject of this study) and Kuhjoch (Global Stratotype Section and Point, GSSP) within the Eiberg basin, shown on a schematic tectonic map of the Northern Calcareous Alps (modified from Hillebrandt & Krystyn, 2009).
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The Triassic-Jurassic boundary (TJB) is marked by one of the five largest Phanerozoic mass extinctions. To constrain existing models for TJB events, we obtained a stratigraphically highly resolved dataset from a marine section at Kendlbachgraben, Austria.
The topmost Triassic Kössen Formation contains low to medium-charged smectite and vermiculite...
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Context 1
... including clay mineralogical data, from the Kendlbachgraben section in the Northern Calcareous Alps in Austria. Palaeogeographically, the studied section belongs to the Eiberg basin, which is also host to the Kuhjoch section, recently chosen as the Global Stratotype Section and Point (GSSP) for the base of Jurassic ( Hillebrandt et al., 2007) (Fig. ...
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... carbonate dissolution of sample KB-1, the >45 mm fraction of the residue contained pale bluish-green clay spherules, which exhibit perfect round or droplet shapes (Fig. 10). Moreover, some angular shaped grains were also found. The Clay mineralogy at the Triassic-Jurassic boundary chemical compositions of the individual grains, measured by EDX, are given in Table 1. Their formulae could not be calculated for 4 tetrahedral + 2 octahedral cations (supposing true dioctahedrality) and deducing the Fe 2+ ...
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... resistant to transportation processes; thus the preservation of the original shape of the spherules argues strongly that they most probably settled directly from the atmosphere without any significant transportation. Impact origin is a possible alternative interpretation of the spherules. The surface of some spherules shows incipient vesiculation (Fig. 10), favouring an origin from volatile-bearing lava. Since they are of similar composition, a similar clay mineral alteration is feasible for spherules ejected from an impact crater of mafic origin lithology; but our set of observa-tions at Kendlbachgraben is more compatible with a volcanic origin of the spherules. Michalík et al. (2007) ...
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Citations
... Enhanced continental weathering is a potential mechanism linking volcanic activity and marine environmental perturbations, whereas chemical weathering of silicate rocks contributes to climate stabilization by the drawdown of atmospheric CO 2 (Berner et al., 1983). Local weathering proxies have been widely used for the ETE, such as clay mineralogy (Shen, Yin, Zhang, et al., 2022;Zajzon et al., 2012), paleosols (van de Schootbrugge et al., 2020), and the Os isotope systems , and suggest abrupt changes in the weathering intensity in response to the emplacement of CAMP. However, temporally highly resolved, and accurate constraints on the weathering regime are still scarce for this time interval, partly due to the dearth of continuous marine sedimentary successions across the TJB. ...
The end‐Triassic extinction (ETE) is one of the most severe biotic crises in the Phanerozoic. This event was synchronous with volcanism of the Central Atlantic Magmatic Province (CAMP), the ultimate cause of the extinction and related environmental perturbations. However, the continental weathering response to CAMP‐induced warming remains poorly constrained. Strontium isotope stratigraphy is a powerful correlation tool that can also provide insights into the changes in weathering regime, but the scarcity of ⁸⁷Sr/⁸⁶Sr data across the Triassic‐Jurassic boundary (TJB) hindered the use of this method. Here we present new high‐resolution ⁸⁷Sr/⁸⁶Sr data from bulk carbonates at Csővár, a continuous marine section that spans 2.5 Myrs across the TJB. We document a continuing decrease in ⁸⁷Sr/⁸⁶Sr ratio from the late Rhaetian to the ETE, terminated by a 300 kyr interval of a flat trend and followed by a transient increase in the early Hettangian that levels off. We suggest that the first in the series of perturbations is linked to the influx of non‐radiogenic Sr from the weathering of freshly erupted CAMP basalts, leading to a delay in the radiogenic continental weathering response. The subsequent rise in ⁸⁷Sr/⁸⁶Sr after the TJB is explained by intensified continental crustal weathering from elevated CO2 levels and reduced mantle‐derived Sr flux. Using Sr flux modeling, we also find support for such multiphase, prolonged continental weathering scenarios. Aggregating the new data set with published records employing an astrochronological age model results in a highly resolved Sr isotope reference curve for an 8.5 Myr interval around the TJB.
... However, a distinctive red clayey-silty interval, the Schattwald Beds, occurs in several sections in this part of the NCA. The Schattwald Beds contain high kaolinite and haematite content, therefore, provide evidence for increased silicate weathering across the TJB interval in the area (Zajzon et al. 2012). ...
Bauxite deposits are residuals of intense lateritic weathering under warm and humid palaeoclimates. The Triassic–Jurassic Boundary (TJB) interval in the Salt Range, Pakistan, provides one such case of bauxite deposits formation along the SW tropical Neo-Tethyan passive margin. Thick, red bauxites/bauxitic clays occur at the contact of the Upper Triassic Kingriali Formation and the Lower Jurassic Datta Formation. These bauxites are rich in kaolinite, haematite, boehmite (Al2O3 and Fe2O3), and are depleted in silica (SiO2). Geochemical proxies of the succession signal intense chemical weathering of the parent siliciclastics under Mesozoic “greenhouse” conditions. Certain trace elements and Rare Earth Elements (REEs) are enriched up to seven times compared to mean Upper Continental Crust (UCC) values. These bauxites are synchronous with the Amir-Abad bauxites of the Alborz Mountains, central Iranian Plateau, that occur between the thick Triassic dolomite/dolomitic limestones of the Elika Formation and the Lower Jurassic Shemshak Formation. Thus, the Salt Range, Pakistan, provides evidence for the eastward extension of the Irano-Himalayan bauxites that are extended westward into Mediterranean bauxites, and the western Tethys by correlation with European bauxites. The TJB bauxites in the Salt Range support increased chemical weathering on the SW Neo-Tethyan passive margin and correspond to an associated sea-level fall during this time interval. This supports the Neo-Tethyan tectonics contribution in the formation of bauxite deposits during the Triassic–Jurassic in addition to the widely studied karst-bauxites that formed in response to the subduction and orogenic processes in the Paleo-Tethys.
... . Moreover, there is now geochemical and sedimentary evidence from marine sections that CAMP volcanism coincided with the ETE33,34 . Subsequent to the earlier work 30,31 , elevated Ir was identified at multiple horizons below the North Mountain Basalt (NMB) in the uppermost Blomidon Formation (Upper Triassic) in the Fundy basin(Fig. ...
Anomalous levels of iridium in sedimentary strata are associated with mass extinction events caused by impact events. In the case of the end-Triassic extinction event, the anomalies as well as the extinctions are linked to the eruption of the Central Atlantic Magmatic Province (CAMP) flood basalts. We report new data on concentrations of iridium in continental strata of the Fundy, Deerfield, Hartford and Newark basins, both above and below the oldest CAMP flows in these basins, that demonstrate that these anomalies are more common than previously known. We conclude that the enrichments were at least in some instances likely derived locally by concentration due to leaching directly from the lavas into sediments proximal to the CAMP flows due to post-eruptive hydrothermal activity. In other instances, the enrichments likely record the global fallout of aerosols and/or ash particles during the eruptions of the CAMP basalts. The common association of the highest levels of enrichment with organic matter suggests either redox control or stabilization by formation of organometallic complexes following post-eruptive redistribution. These findings demonstrate the importance of considering the distribution and magnitude of iridium anomalies in considering the source of the iridium and possible extinction mechanisms.
... Increased amounts of kaolinite encountered in boundary beds across NW Europe have been taken as evidence for extremely humid conditions (van de Schootbrugge et al., 2009;Zajzon et al., 2012;Lintnerová et al., 2013). In Scania (Sweden), high amounts of kaolinite were identified in the uppermost Rhaetian Bjuv Member (Lindström and Erlström, 2006). ...
Soils are a crucial link between the atmosphere, biosphere, and geosphere. Any disturbance to the health of soils will severely impact plants as well as a multitude of organisms living in or on soils, such as fungi, bacteria, and insects. Catastrophic soil loss is thought to have played a pivotal role during mass-extinction events as a result of major deforestation, but the exact feedbacks remain elusive. Here, we assess the role of soil loss during the end-Triassic mass-extinction event based on proxy data obtained from four sediment sections recovered from France, Germany, and Denmark. Clay mineral and palynological data indicate a strong increase in erosion during the latest Rhaetian with the influx of kaolinite and abundantly reworked Palaeozoic and Neoproterozoic organic matter. Based on a new timeline, these changes were coeval with intense volcanic activity in the Central Atlantic Magmatic Province (CAMP). In addition to vegetation dieback, repeated forest fires, as well as widespread seismic activity related to CAMP emplacement led to landscape destruction triggering removal of soils. The biological degradation of fern spore walls by fungi and bacteria, a process coupled to organic matter decay in soils, strongly decreased across the T/J boundary. We interpret this counter-intuitive result as evidence for rapid and widespread removal of soils. Taken together, CAMP induced environmental changes led to profound changes in erosion and removal of soils, while soil resilience during the Hettangian appears to have proceeded hand in hand with recovery in Jurassic seas.
... Beyond establishing the temporal link of CAMP volcanism and the ETE, and the plausible role of LIP-driven environmental changes in triggering the biotic crisis, significant effort went into finding direct markers of volcanism in marine sedimentary sections where the extinction event is best documented. Mafic mineral grains supposedly from air-fallen ash, distinctive clay minerals thought to derive from alteration of basaltic volcanic glass, and anomalous enrichment of rare earth elements (REE) at the TJB in a western Tethyan marine section now exposed in the Northern Calcareous Alps was proposed as distal evidence for coeval CAMP activity Zajzon et al., 2012). In recent years, mercury-concentration and Hg/TOC (Hg data normalized with the total organic carbon content) data have been increasingly used, and proved as a geochemical tracer of distal volcanic activity in sedimentary sections (Grasby et al., 2019 and references therein). ...
The end-Triassic extinction is one of the major Phanerozoic mass extinctions and it appears to have been linked to coeval rapid and severe environmental change, thought to be triggered by volcanism in the Central Atlantic Magmatic Province (CAMP). However, direct stratigraphic evidence to substantiate this linkage and help develop scenarios for the cascade of events is still scarce. Mercury is an increasingly widely used proxy to trace the volcanic activity associated with large igneous provinces (LIPs) in distal sedimentary sections, but so far Hg records are available from only a handful of Triassic–Jurassic boundary (TJB) sections. One of the few well-studied marine sedimentary sections with a continuous sedimentary record across the TJB is located at Csővár (Hungary) and it exposes an extended succession of carbonates deposited in an intraplatform basin on the western Tethyan shelf. Previously, this section yielded one of the first convincing records of carbon isotope excursions (CIE) across the TJB, albeit from low-resolution sampling. Here we report a new, high-resolution δ¹³Ccarb curve, supplemented with Hg measurements. A series of successive negative carbon isotope excursions (termed NCIE-1 to 6) attests to carbon cycle perturbations in the TJB interval. Four excursions appear significant after statistical smoothing. Of these, NCIE-3 exhibits the highest amplitude and is biostratigraphically constrained to the topmost Triassic, hence reliably correlated with the initial CIE, a globally recognised excursion closely preceding the TJB, coincident with the end Triassic extinction (ETE) horizon. The Hg concentration data provide the longest record available to date from a single section across the TJB. It shows very low values below NCIE-3 that are interpreted as the pre-volcanic background, followed by a prominent Hg peak that is nearly coincident with the most significant carbon isotope spike (NCIE-3). The slight lag suggests that onset of a major extrusive phase of CAMP (marked by a significant rise in Hg) closely followed the very onset of carbon cycle perturbation at that time (expressed by an abrupt change in the δ¹³Ccarb signal), possibly from biogenic methane release. Subsequent and recurring smaller Hg peaks suggests a pulsatory nature of prolonged volcanic activity. Organic content in the section is consistently low and sedimentary Hg concentrations are therefore normalized against Fe content, a reliable proxy in the lack of significant lithological changes. The maximum sedimentary Hg concentration at Csővár is greater than that in any other TJB section, although not unprecedented if other events are considered. Three hypotheses are explored to explain the high values; i) the hit-or-miss model could suggest that deposition of the sampled beds was fortuitously coincident with major eruptions, ii) the presence and preservation of cryptotephra could account for the unusually high sedimentary Hg enrichment, and iii) changes in the proportion of Hg-carrier phases throughout the studied succession, e.g. from magnetite to pyrite dominance, could have enhanced the potential of Hg capture. Collectively, the new data provide direct stratigraphic and geochemical evidence for the link between CAMP volcanism and carbon cycle perturbations and strengthen the case of their causal relationship with the end-Triassic extinction.
... The dramatic global warming driven by the release of CO 2 and methane led to a significant increase of extreme climatic events, which may have eventually caused the biotic crises (McElwain et al., 1999;Tanner et al., 2001;Grice et al., 2005;Cleveland et al., 2008;Bacon et al., 2011;Schaller et al., 2012;de Jersey and McKellar, 2013;Mander et al., 2013;Haworth and Raschi, 2014;Williford et al., 2014;Steinthorsdottir et al., 2015). The study of the major perturbations in carbon and sulfur cycling showed that there was an interaction between the terrestrial and marine ecosystems across the TJB (Hesselbo et al., 2002;Williford et al., 2007Williford et al., , 2009Götz et al., 2009;Bonis et al., 2010;Pieńkowski et al., 2012;Zajzon et al., 2012). However, the duration and environmental background of the end-Triassic mass extinction remain under debate. ...
The end-Triassic mass extinction is one of the five big extinction events in the Phanerozoic, and its impact on marine organisms has been extensively studied. However, whether the terrestrial ecosystem had begun to deteriorate or even collapsed prior to the end-Triassic mass extinction remains controversial and the related studies in Asia are very limited. In this study, we provide a comprehensive investigation of the sedimentary environments, their implications for floral changes, and the paleoecology during the Norian–Rhaetian transition in Xuanhan area, northeastern Sichuan Basin, Southwest China. The sedimentary environments and climatic conditions changed coupling the transgression and regression caused by the tectonic movements. Climatic oscillations were identified during the Norian–Rhaetian transition in the Xuanhan area, including a short-term cooling event. The diversity and composition of the plant communities changed through the Norian–Rhaetian transition in Xuanhan area, but the terrestrial ecosystem as a whole didn’t collapse or deteriorate prior to the end-Triassic mass extinction.
... Nevertheless, a most Fig. 8. Boxplots of δ 13 C TOC of the combined sites in the NCA binned for three stratigraphically distinct units (Section 5.2), compiling data from the Restentalgraben, Tiefengraben, Kendlbachgraben, Kuhjoch and Hochalplgraben sections (Kuerschner et al. 2007, Ruhl et al. 2009). The Kendlbachgraben and Tiefengraben lithological subdivision is based on clay mineralogy analysis by Zajzon et al. (2012) and a change to a more silty lithology (Kuerschner et al. 2007), respectively. Age of the lower Schattwald Beds is after Lindström et al. (2017 b) and Korte et al. (2019); the age of the Tr-J boundary is after Wotzlaw et al. (2014). ...
Stratigraphic studies are an integral component in understanding the chronology of events that led to the end-Triassic mass extinction, by resolving causal relationships between environmental upheavals and biotic response. Successful correlation of Triassic–Jurassic (Tr–J) successions is complicated by the disappearance of macro-fossils that are otherwise central components in stratigraphic studies. This problem is exacerbated in multiple Tr–J sections situated in Europe, where the so-called “Event Beds” – assumed to demarcate the extinction interval – are virtually devoid of fossils. An alternative stratigraphic approach entails the reconstruction of carbon isotope records, where stratigraphic fluctuations in carbon isotope composition are considered to track changes in the global biogeochemical carbon cycle. The predominance of carbonate-lean sections has prompted the reconstruction of total organic carbon (TOC)-based carbon isotope records. However, bulk rock derived TOC is the diagenetically stabilized remnant of organic components that accumulated on the sea floor, and which can originate from multiple sources. In this study, we assess long-term TOC-based carbon isotope trends at two sites: Bonenburg (Central European Basin) and Kuhjoch (the Tr–J Global Stratotype Section and Point; western Tethys shelf seas). We focus on the TOC 13C-enrichment of the Event Beds with the aim of deciphering stratigraphic fluctuations in relation to their main driver (the exogenic carbon pool versus organic matter source changes). By studying the systematic co-variance of several sedimentary parameters (TOC, total nitrogen [TN], and the palynomorph composition), we infer that the TOC composition is possibly characterized by insignificant organic matter source changes in terms of the marine and terrestrial organic carbon contributions. By contrast, a clay mineralogical shift to more K-depleted minerals as well as the elevated occurrence of wood fragments in the Event Beds suggest a terrestrial organic matter source shift from immature substrates to substrates predominated by “pre-aged” or “fossil organic matter” under a changing continental weathering regime. This outcome urges for reservations when interpreting TOC-based carbon isotope records in terms of global C-cycle perturbations, especially when coinciding with lithological and mineralogical changes. On a more positive note, the shift towards positive carbon isotope values appears to be a recurring feature, possibly testifying to a globally significant climate-controlled weathering regime shift.
... Additionally, Pálfy and Kocsis (2014) noted that increased fire frequency is more likely to promote floral diversity, rather than suppress it, as is apparently the case in the East Greenland and Danish sections (Belcher et al. 2010;Petersen and Lindström 2012). Stronger evidence for warming at the boundary is provided by the long-noted change in clay mineralogy in which the proportion of kaolinite increases sharply (van de Schootbrugge et al. 2009;Pieńkowski et al. 2012;Zajzon et al. 2012). Ostensibly, this increase resulted from strongly tropical weathering conditions under the enhanced greenhouse climate following the eruptions. ...
The fossil record of Late Triassic tetrapods can be organized biostratigraphically and biochronologically into five, temporally successive land-vertebrate faunachrons (LVFs) that encompass Late Triassic time (in ascending order): Berdyankian, Otischalkian, Adamanian, Revueltian and Apachean. An up-to-date review of the age constraints on Late Triassic tetrapod fossil assemblages and correlation within the framework of the LVFs is presented. This makes possible a much more accurate evaluation of the timing of biotic events of Late Triassic tetrapod evolution, including: (1) Otischalkian, HO (highest occurrence) of almasaurids and chroniosuchians?, LOs (lowest occurrences) of crocodylomorphs and dinosaurs; (2) Adamanian, HO of mastodonsaurids and trematosaurids, LO of mammals; (3) Revueltian, HOs of capitosaurids, rhynchosaurs and dicynodonts; and (4) Apachean, HOs of metoposaurids, plagiosaurids and aetosaurs. The LO of turtles is Early Triassic or older, and the HO of phytosaurs is an Early Jurassic record. There is no compelling evidence of tetrapod mass extinctions at either the Carnian-Norian or the Triassic-Jurassic boundaries.
... The application of the climate and environment information records documented in paleosoil has become a hot spot for the earth sciences ( Nedachi et al., 2005;Sedov et al., 2003). The assemblage, relative content and crystallinity of clay minerals in paleosoil have been widely used in the reconstruction of the paleoclimate( Das et al., 2013;Fonseca et al., 2007;Hong et al., 2009;Ji et al., 2002;Liu et al., 2003;Xie et al., 2013;Zajzon et al., 2012). The clay minerals of mixed-layer clay minerals formed in the relatively narrow climate conditions are quite sensitive to the climate changes. ...
Mineralogy and genesis significance of mixed-layer illite-vermiculite in Xuancheng red soil section were investigated using X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), and inductively coupled plasma emission spectrum (ICP-AES). XRD shows that clay minerals in the red soils are composed of illite, vermiculite, mixed-layer illite-vermiculite, and kaolinite. The lattice fringes of mixed-layer illite-vermiculite were directly observed under HRTEM. Vermiculite layers were trapped within the illite layers, indicating that mixed-layer illite-vermiculite was derived from illite. The higher content of vermiculite, mixed-layer illite-vermiculite, and kaolinite in the net-like red soil relative to the homogeneous red soil suggested a warmer and more humid climate prevailing over the mid-Pleistocene and a relatively cool and dry climate prevailing over the late Pleistocene. A lower hydroxy-Al hydroxides content of the vermiculitic layers in the net-like red soil compared to those of the homogeneous red soil resulted in more tortuous lattice fringes. Hence, Mixed-layer illite-vermiculite with hydroxy-Al hydroxides interlacated is sensitive to the climatic environment change in soil-forming process.
... Apart from the comprehensive description of the GSSP at Kuhjoch presented inHillebrandt et al. (2013), several papers have dealt with the macropalaeontology (Hillebrandt and Krystyn, 2009), palynology (Bonis et al., 2009), organic C-isotope stratigraphy (Ruhl et al., 2009) and geochemistry (Tanner et al., 2016), of the Kuhjoch section. Several studies have focused on other TJB successions located within the same basin, the Eiberg Basin, providing additional important information concerning C-isotopes (Mette et al., 2012), micropalaeontology (Clémence et al., 2010b), geochemistry and mineralogy (Pálfy and Zajzon, 2012), and clay mineralogy (Zajzon et al., 2012) of the boundary succession. The last occurrence of Triassic choristoceratid ammonoids, as well as the first appearance of Jurassic psiloceratid ammonites allow these sections in the Northern Calcareous Alps to be correlated with TJB successions in British Columbia (Canada;Ward et al., 2001Ward et al., , 2004), Nevada (USA;Guex et al., 2004Guex et al., , 2009Ward et al., 2007) and Peru (Hillebrandt, 1994Hillebrandt, , 1997Hillebrandt, , 2000aHillebrandt, , 2000bSchoene et al., 2010). ...
Understanding the end-Triassic mass extinction event (201.36 Ma) requires a clear insight into the stratigraphy of boundary sections, which allows for long-distance correlations and correct distinction of the sequence of events. However, even after the ratification of a Global Stratotype Section and Point, global correlations of TJB successions are hampered by the fact that many of the traditionally used fossil groups were severely affected by the crisis. Here, a new correlation of key TJB successions in Europe, U.S.A. and Peru, based on a combination of biotic (palynology and ammonites), geochemical (δ¹³Corg) and radiometric (U/Pb ages) constraints, is presented. This new correlation has an impact on the causality and temporal development during the end-Triassic event. It challenges the hitherto used standard correlation, which has formed the basis for a hypothesis that the extinction was caused by more or less instantaneous release of large quantities of light carbon (methane) to the atmosphere, with catastrophic global warming as a consequence. The new correlation instead advocates a more prolonged scenario with a series of feedback mechanisms, as it indicates that the bulk of the hitherto dated, high-titanium, quartz normalized volcanism of the Central Atlantic Magmatic Province (CAMP) preceded or was contemporaneous to the onset of the mass extinction. In addition, the maximum phase of the mass extinction, which affected both the terrestrial and marine ecosystems, was associated with a major regression and repeated, enhanced earthquake activity in Europe. A subsequent transgression resulted in the formation of hiati or condensed successions in many areas in Europe. Later phases of volcanic activity of the CAMP, producing low titanium, quartz normalized and high-iron, quartz normalized basaltic rocks, continued close to the first occurrence of Jurassic ammonites and the defined TJB. During this time the terrestrial ecosystem had begun to recover, but the marine ecosystem remained disturbed.
