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Morphometric measurements of ammonite shells. The five derived shape ratios used in this study are: D 1⁄4 c/d; S 1⁄4 b/a; W 1⁄4 (d/e) 2 ; RW 1⁄4 b/T; AH 1⁄4 f/a.
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The Pliensbachian–Toarcian interval was marked by major environmental disturbances and by a
second-order mass extinction. Here, we reappraise the taxonomic, spatiotemporal and selective dynamics of
extinctions over the whole interval, by analysing a high-resolution dataset of 772 ammonite species from NW
Tethyan and Arctic domains. On average, 40–6...
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... morphology of each species was described using five morphometric parameters measured on entire adult shells (Fig. 3), thus obviating ontogenetic considerations ( Gerber et al. 2008). The characters retained correspond to the whorl expansion rate (W), the umbilical expansion rate (D), and the whorl shape (S). They represent the basic theoretical parameters defined by Raup & Michelson (1965), which may be related to the buoy- ancy, swimming velocity, ...
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Citations
... The T-OAE nCIE is believed to be associated with rapid, large-scale CO 2 release from the Karoo-Ferrar Large Igneous Province (LIP), methane hydrate of continental margins or terrestrial environments of wetlands, soils, and lakes (Hesselbo and Jenkyns, 1998;Hesselbo et al., 2000Hesselbo et al., , 2007Pálfy and Smith, 2000;Them II et al., 2017). Thus, large-scale changes in climate and environmental perturbations were triggered, such as accelerated global warming (Dera et al., 2010;Korte et al., 2015), significant sea-level rise (Hallam, 1981;Haq, 2018), enhanced continental weathering (Brazier et al., 2015;Percival et al., 2016;Kemp et al., 2020), ocean acidification (Müller et al., 2020), and biotic crisis (Harries and Little, 1999;Caswell and Coe, 2014;Jiang et al., 2020). ...
... The Toarcian oceanic anoxic event (T-OAE; ~ 183 Ma) is the oldest of these Mesozoic events (Jenkyns 1985(Jenkyns , 1988. It is characterised by global climate change (Ruebsam and Schwark 2021 and references therein), mass extinction of marine biota (e.g., Harries and Little 1999;Pálfy and Smith 2000;Dera et al. 2010;Caruthers et al. 2013), and a prominent negative carbon isotope shift (3-8‰) referred to as the Toarcian Carbon Isotope Excursion (T-CIE) (e.g., Hesselbo et al. 2000Hesselbo et al. , 2007. ...
The Posidonia Shale in the basement of the North Alpine Foreland Basin of southwestern Germany represents an important archive for environmental changes during the Toarcian oceanic anoxic event and the associated carbon isotope excursion (T-CIE). It is also an important hydrocarbon source rock. In the Salem borehole, the Posidonia Shale is~10 m thick. The lower 7.5 m (1763.5–1756.0 m) of the Posidonian Shale and the uppermost part of the underlying Amaltheenton Formation were cored and studied using a total of 62 samples. Rock–Eval, palynological, maceral, biomarker and carbon isotope data were collected to assess variations in environmental conditions and to quantify the source rock potential. In contrast to most other Toarcian sections in southwest Germany, TOC contents are high in sediments deposited during the T-CIE, but reach a peak in post-CIE sediments. Biomarker ratios suggest that this refects strong oxygen-depletion during the T-CIE (elegantulum to lower elegans subzones), but also during the falciferum Subzone, which is also refected by a prolonged dinofagellate cyst blackout. While sediments of the tenuicostatum Zone to the elegans Subzone are thinner than in neighbouring sections (e.g., Dotternhausen), sediments of the falciferum Subzone are unusually thick, suggesting that increased
subsidence might have contributed to anoxia. The T-CIE interval is very thin (0.75 m). δ13C values of n-alkanes show that the maximum negative isotope shift predates the strongest basin restriction during the T-CIE and that the carbon isotope shift is recorded earlier for aquatic than for terrigenous organisms. In Salem, the Posidonia Shale is thermally mature and highly oil-prone. The residual source petroleum potential is about 0.8 tHC/m2.
... The T-OAE NCIE also coincided with a faunal turnover, which remains relatively understudied. Some studies have documented a collapse in genus-and species-level marine biodiversity in ammonoids and foraminifera during the early Toarcian coeval with the NCIE (e.g., Dera et al., 2010;Caruthers et al., 2013;Gori can et al., 2013), and others have proposed a link between the environmental perturbations that triggered the T-OAE and a nonmarine faunal turnover in dinosaurs, with relic taxa like coelophysoid theropods, non-eurypod thyreophorans, and non-sauropod sauropodomorphs going extinct during the Toarcian (Reolid et al., 2022). ...
... The incipient radiation of macropredatory pliosaurids has been associated with a landmark turnover of Earlyto-Middle Jurassic marine reptile assemblages inhabiting the northwestern Tethyan epicontinental periphery of what is today western Europe 22 . Notably, this coincides with abrupt oceanic cooling over the earliest Middle Jurassic interval (Aalenian, ~ 174.7 Ma) 92 , and accompanying extinctions affecting nektonic invertebrates, in particular cephalopods 93,94 . The ensuing recovery of major belemnite (Belemnopseina) 93 and ammonite (Ammonitina) 94 groups was distinguished by biogeographical provincialism, involving separation into distinct Tethyan and Boreal faunas 93,95 . ...
... Notably, this coincides with abrupt oceanic cooling over the earliest Middle Jurassic interval (Aalenian, ~ 174.7 Ma) 92 , and accompanying extinctions affecting nektonic invertebrates, in particular cephalopods 93,94 . The ensuing recovery of major belemnite (Belemnopseina) 93 and ammonite (Ammonitina) 94 groups was distinguished by biogeographical provincialism, involving separation into distinct Tethyan and Boreal faunas 93,95 . ...
... In summary, our results demonstrate that thalassophonean pliosaurids were the geologically longest-ranging clade of macropredatory marine tetrapods with a fossil record spanning ~ 80 Ma. Their advent paralleled a regional marine faunal turnover in the earliest Middle Jurassic 22,93,94 that was perhaps associated with rapid oceanic temperature changes and the progressive decline of coeval macrophagous marine reptiles specialised for feeding on cephalopods 97 . These included coeval large-bodied rhomaleosaurids 90 , which persisted until the latest Middle Jurassic 91 but were likely not direct competitors. ...
The emergence of gigantic pliosaurid plesiosaurs reshaped the trophic structure of Mesozoic marine ecosystems, and established an ~80 million-year (Ma) dynasty of macropredatory marine reptiles. However, the timescale of their ‘defining’ trait evolution is incompletely understood because the fossil record of gigantic pliosaurids is scarce prior to the late-Middle Jurassic (Callovian), ~165.3 Ma. Here, we pinpoint the appearance of large body size and robust dentitions to early-Middle Jurassic (Bajocian) pliosaurids from northeastern France and Switzerland. These specimens include a new genus that sheds light on the nascent diversification of macropredatory pliosaurids occurring shortly after the Early-Middle Jurassic transition, around ~171 Ma. Furthermore, our multivariate assessment of dental character states shows that the first gigantic pliosaurids occupied different morphospace from coeval large-bodied rhomaleosaurid plesiosaurs, which were dominant in the Early Jurassic but declined during the mid-Jurassic, possibly facilitating the radiation and subsequent ecomorph acme of pliosaurids. Finally, we posit that while the emergence of macropredatory pliosaurids was apparently coordinated with regional faunal turnover in the epeiric basins of Europe, it paralleled a globally protracted extinction of other higher trophic-level marine reptiles that was not completed until after the earliest-Late Jurassic, ~161.5 Ma.
... Ammonite faunas from high Northern Hemisphere latitudes indicate multiple peaks and troughs in extinction rates that suggest there were several phases of extinction in the Pliensbachian and Toarcian (O'Dogherty et al. 2000, Dera et al. 2010, with a major diversity peak followed by a sharp decline in the late Bifrons Zone (Caruthers et al. 2013(Caruthers et al. , 2014. Riccardi (2008) recorded a peak and decline at about the same level in Argentina. ...
The Late Triassic spiriferinides of Zealandia include the endemic or Austral genera Rastelligera, Psioidea and Psioidiella, and the cosmopolitan Zugmayerella. Mentzelia kawhiana is revised and placed in Callospiriferina. It appears in the late Rhaetian and is found in the Téremba Terrane in New Caledonia and throughout the Murihiku Terrane in New Zealand. The spiriferinides were severely affected at the Triassic–Jurassic boundary in Zealandia as elsewhere, but a moderately diverse fauna developed in the Early Jurassic. This has strong links to South America, and affinities with southern Europe and North Africa. In this study, a total of six species of Jurassic spiriferinides are recognised. Callospiriferina ongley is present in middle and late Hettangian and Sinemurian faunas. It is succeeded in the Pliensbachian and early Toarcian by Callospiriferina radiata. Two species of Spiriferina are recognised. S. sophiaealbae n. sp. first appears in the Middle Hettangian and is present in the Southland and Kawhia Synclines until the early Toarcian. S. arakiwa n. sp. is found mainly on the southwest limb of the Southland Syncline in the Pliensbachian and early Toarcian. The non-costate European genus Cisnerospira is represented in Zealandia by the small C. antipoda n. sp. This species ranges from Hettangian to early Toarcian. Two specimens of a spiriferinide with a costate sulcus are tentatively identified as Dispiriferina sp. cf. D. chilensis. The highest stratigraphic level at which Zealandian spiriferinides have been found is that of the Dactylioceras band at Kawhia, which is correlated with the Crassum Subzone of the Bifrons Zone (highest Early Toarcian) and includes three species of spiriferinide. This suggests that the Zealandian spiriferinides survived the Toarcian Event, only to meet their demise slightly later.
... The Late Pliensbachian to Early Toarcian is considered as a period of hot Earth in the Jurassic, with successive Pliensbachian-Toarcian boundary events (Pl-To boundary) and Toarcian oceanic anoxic events (T-OAE) (Suan et al., 2008;Littler et al., 2010;Dera et al., 2010;Dera et al., 2011;Mailliot et al., 2010;Percival et al., 2015;Ruhl et al., 2016;Xu et al., 2017Xu et al., , 2018Ikeda et al., 2018;Storm et al., 2020). This period is noticeable for its widespread organic carbon burial and the associated environmental and climatic oscillations, including wildfire activity, global carbon cycle perturbation, sea level rising, global warming, enhanced chemical weathering and accelerated hydrological cycle (Hesselbo et al., 2000;Cohen et al., 2004;Gómez et al., 2008;Suan et al., 2008;Jenkyns, 2010;Dera et al., 2010;Dera et al., 2011;Pittet et al., 2014;Little and Benton, 2015;Percival et al., 2016;Baker et al., 2017;Them-II et al., 2019). ...
... The Late Pliensbachian to Early Toarcian is considered as a period of hot Earth in the Jurassic, with successive Pliensbachian-Toarcian boundary events (Pl-To boundary) and Toarcian oceanic anoxic events (T-OAE) (Suan et al., 2008;Littler et al., 2010;Dera et al., 2010;Dera et al., 2011;Mailliot et al., 2010;Percival et al., 2015;Ruhl et al., 2016;Xu et al., 2017Xu et al., , 2018Ikeda et al., 2018;Storm et al., 2020). This period is noticeable for its widespread organic carbon burial and the associated environmental and climatic oscillations, including wildfire activity, global carbon cycle perturbation, sea level rising, global warming, enhanced chemical weathering and accelerated hydrological cycle (Hesselbo et al., 2000;Cohen et al., 2004;Gómez et al., 2008;Suan et al., 2008;Jenkyns, 2010;Dera et al., 2010;Dera et al., 2011;Pittet et al., 2014;Little and Benton, 2015;Percival et al., 2016;Baker et al., 2017;Them-II et al., 2019). The environment events have been widely reported in marine or terrestrial strata globally. ...
... The Karoo LIP has not been linked to any major mass extinction but could have contributed to less severe, second order marine extinctions, OAE, and global warming during the Pliensbachian-Toarcian. The marine extinctions are recognizable at the species and genus levels and are multi-phased, with the main phase occurred at the Pliensbachian-Toarcian boundary (Dera et al., 2010;Caruthers et al., 2013). The anoxic event, which postdates the Pliensbachian-Toarcian extinction and occurred in the early Toarcian, is marked by global deposition of black shale (Jenkyns, 1988) and negative carbon isotope excursion (e.g., Suan et al., 2008). ...
... Other processes documented during the Jenkyns Event include: (1) a perturbation of the carbon cycle evidenced as a negative carbon isotopic excursion (CIE; e.g., Jenkyns & Clayton, 1986;Kemp et al., 2005;Hesselbo et al., 2007;Ruebsam et al., 2019Ruebsam et al., , 2020a; (2) oxygen depleted conditions in some marine basins, the Toarcian Oceanic Anoxic Event (T-OAE, Gill et al., 2011;Fonseca et al., 2018;Izumi et al., 2018;Ruebsam et al., 2018;Suan et al., 2018); (3) a sea-level rise (e.g., Hallam, 1981;Pittet et al., 2014;Haq, 2018;Krencker et al., 2019); and (4) a crisis of marine carbonate productivity (Bucefalo-Palliani et al., 2002;Mattioli et al., 2004) and acidification (Müller et al., 2020;Ettinger et al., 2021). In the context of environmental change, the early Toarcian is also characterized by a second-order extinction that affected marine ecosystems, including dynoflagellate cysts, foraminifera, ostracods, brachiopods, corals, bivalves, and cephalopods (e.g., Hallam, 1987;Little & Benton, 1995;Harries & Little, 1999;Aberhan & Fürsich, 2000;Macchioni & Cecca, 2002;Vörös, 2002;Arias, 2009Arias, , 2013Dera et al., 2010;García Joral et al., 2011;Caruthers et al., 2014;Baeza-Carratalá et al., 2017;Reolid et al., 2019;Vasseur et al., 2021;Reolid & Ainsworth, 2022). In addition to the extinction, the biotic crisis is also expressed in a decrease of diversity, mainly affecting benthic communities, as well reductions in body size of some taxa (Harries & Little, 1999;Piazza et al., 2020). ...
The early Toarcian Jenkyns Event (~183 Ma) was characterized by a perturbation of the global carbon cycle, global warming, which at continental areas led to intensifi ed chemical weathering, enhanced soils erosion, and intensifi ed wildfi res. Warming and acid rain aff ected diversity and composition of land plant assemblages, caused a loss of forests and thereby impacted on trophic webs. The Jenkyns Event, triggered by volcanic activity of the Karoo-Ferrar Large Igneous Province, changed terrestrial ecosystems, and also aff ected the dinosaurs. Fossil macroplant assemblages and palynological data reveal reductions in the diversity and richness of plant communities. A substantial loss of land plant biomass and a shift to forests dominated by Cheiropelidiaceae conifers occurred as a consequence of seasonally dry and warm conditions. Major changes occurred to hervivore dinosaurs, with extinction of diverse basal families of Sauropodomorpha ('prosauropods') as well as some basal sauropods. Ornithischian dinosaurs show patchy records; some heterodontosaurids disappeared and the scelidosaurids (Thyreophora) went extinct during the Jenkyns Event. The dominant carnivorous dinosaurs, the Coelophysoidea (Theropoda), died out during the Jenkyns Event. We interpret the Jenkyns Event as a terrestrial crisis for ecosystems, marked especially by fl oral changes and the extinction of some dinosaur clades, both hervivores and carnivores.
Resumen: El Evento Jenkyns del Toarciense inferior (~183 Ma) se caracterizó en ambientes continentales por una perturbación del ciclo del carbono, un calentamiento global, un aumento de la meteorización, la pérdida de suelos y la proliferación de incendios. El calentamiento y la lluvia ácida afectaron a la diversidad y composición de las asociaciones vegetales, causó la pérdida de masas forestales y tuvo un fuerte impacto en las redes trófi cas. El Evento Jenkyns, cuyo detonante fue la intensa actividad volcánica de la Provincia Ígnea de Karoo-Ferrar, cambió los ecosistemas continentales, afectando entre otros a los dinosaurios. Los datos palinológicos y de las asociaciones fósiles de macroplantas muestran una reducción de la diversidad y la riqueza de las comunidades vegetales, especialmente una pérdida de biomasa y la dominancia de coníferas cheirolepidiáceas en los bosques, en un contexto de condiciones cálidas estacionalmente áridas. Pueden observarse cambios importantes entre los dinosaurios herbívoros con la extinción de varias familias basales de sauropodomorfos ("prosaurópodos") y algunos saurópodos basales. Los dinosaurios ornitisquios, pese a su registro más incompleto, muestran la desaparición de algunas especies de heterodontosáuridos y la extinción de la familia Scelidosauridae (Thyreophora) en relación con el Evento Jenkyns. Los dinosaurios carnívoros de la superfamilia Coelophysoidea (Theropoda) también se extinguieron durante el Evento Jenkyns. Por lo tanto, se interpreta que el Evento Jenkyns contituyó una crisis biótica en los ecosistemas continentales de gran importancia, marcada especialmente por cambios en la fl ora y la extinción de algunos grupos de dinosaurios tanto herbívoros como carnívoros.
... The T-OAE was also associated with widespread deposition of organic-rich black shales in marine settings, reflecting extensive development of bottomwater anoxia/euxinia (e.g., Wignall et al., 2005). These environmental changes contributed to a marine biocrisis that severely impacted many animal clades including ammonoids, belemnites, foraminifera, brachiopods, calcareous nannofossils, and ostracods (e.g., Raup and Sepkoski Jr., 1984;Sepkoski Jr., 1996;Dera et al., 2010Dera et al., , 2011Jiang et al., 2020), and that also markedly altered endobenthic faunal dynamics (see review by Rodríguez-Tovar, 2021). ...
Despite carbon-cycle perturbations at a global scale during the early Toarcian, the extent of anoxia during the ~182-Ma Toarcian Oceanic Anoxic Event (T-OAE) remains in debate. A common actor in the development of oceanic anoxia is watermass restriction, which is thought to have been important in the NW European Seaway, but whose influence elsewhere is relatively unstudied. Here, we analyze Mo/TOC (a proxy for watermass restriction) and redox proxies (e.g., Corg/P) in two sections of the Asturian Basin (northern Iberian Paleomargin), and we integrate these results with data from a suite of global Toarcian sections in order to reassess the relationship of euxinia and local hydrographic restriction during the T-OAE. The Asturian Basin study sections accumulated in oxic to dysoxic waters, punctuated by two episodes of intermittently euxinic bottomwaters or
porewaters around the Tenuicostatum/Serpentinum zonal boundary. This area was an unrestricted carbonate ramp
during the T-OAE that was not sufficiently reducing for its Mo/TOC ratios (2.3–4.5) to accurately record the
degree of watermass restriction. Regionally, Lower Toarcian black shales exhibit elevated Mo and TOC concentrations
(21–42 ppm Mo, 12–18% TOC) along with exceptionally low mMo/TOC (e.g., ~0.3 in the Paris Basin,
~0.4 in the Cleveland Basin, and ~ 2.0 in the Qiangtang Basin), providing evidence of highly restricted, euxinic
bottomwaters in Northwestern (epicontinental intrashelf troughs) and Eastern (barrier-lagoon) Tethyan settings.
In contrast, in other basins across the SW Tethys and Panthalassic oceans, low contents of Mo and TOC (mostly
<5 ppm Mo, <3% TOC) indicate unrestricted watermass conditions and at most intermittent bottomwater or
porewater euxinia in pelagic to hemipelagic environments, although intermittently euxinic bottomwaters
developed also in deep open-marine settings. The results of our analysis support both (1) a major role for hydrographic
restriction in modulating the local expression of the T-OAE in various regions globally, and (2) a
substantial drawdown of aqueous Mo in the global ocean during the T-OAE, indicating that existing hypotheses
regarding the nature of the T-OAE event are not mutually exclusive.
... The late Early Jurassic has experienced one of the most severe environmental perturbations of the Mesozoic, leading to a 2nd-order mass extinction event affecting both pelagic and benthic organisms (Little and Benton, 1995;Dera et al., 2010;Caruthers et al., 2013;Danise et al., 2013;Vasseur et al., 2021). Due to presence of organic matter-rich deposits and a large negative carbon isotope excursion in the lower Toarcian levisoni zone (Hesselbo et al., 2007;Jenkyns, 2010;Suan et al., 2010), the Toarcian Oceanic Anoxic Event (T-OAE) is the most iconic expression of this Early Jurassic environmental perturbation, and has hence been the focus of numerous studies (e.g. ...
... Of importance here is that the early Toarcian mass extinction event is a two-fold event, with a first episode occurring at the Pliensbachian/Toarcian (Pl/To) boundary, and a second one at the onset of the T-OAE (Little and Benton, 1995;Cecca and Macchioni, 2004). Of these two episodes, the Pl/To event is the one that had the strongest impact on the biosphere (Dera et al., 2010;Caruthers et al., 2013;Brame et al., 2019;Vasseur et al., 2021), inducing a global collapse of pelagic and neritic carbonate production (Dromart et al., 1996;Suan et al., 2010;Menini et al., 2019;Krencker et al., 2020). ...
The Pliensbachian/Toarcian boundary (Pl/To) event precedes by ca. 1 Myr the onset of the Toarcian Oceanic Anoxic Event. It corresponds to a second order mass extinction associated with an outstanding collapse of shallow marine ecosystems at global scale. Yet, our knowledge about its exact driver(s) and unfolding is relatively ambiguous due to the numerous hiatuses present in the sedimentary record during this critical time interval. In this study, an integrated carbon isotope chemostratigraphy and sequence stratigraphy approach is applied to two case studies (the upper Pliensbachian in South-East France and the Pliensbachian–Toarcian transition in Morocco) to demonstrate how the major changes in sea-level and sedimentation supply accompanying the Pl/To event led to the formation of ubiquitous, often cryptic hiatal surfaces in the sedimentary record. Hence, as a consequence of strongly progradational stacking pattern during the latest Pliensbachian related to a global sea-level lowstand associated with cold greenhouse climate, proximal settings were characterized by bypass and/or erosion, inducing an incomplete record of the Spinatum chronozone in localities situated in the outer part of sedimentary basins. In the earliest Toarcian, the collapse of the neritic carbonate factory led to a halt of carbonate mud export into the basin, resulting in sediment starvation in most basins characterized by a carbonate-dominated sedimentation regime before the environmental perturbation. Only localities where vigorous siliciclastic sediment supply took over are likely to have a more complete sedimentary record of the immediate aftermath of the carbonate production collapse. This combination of causes explains the ubiquitous incompleteness of the record of the Pliensbachian/Toarcian transition in numerous European localities where the bulk of our current understanding about the Pl/To event derives from. A comparison between the two known most expanded and complete records of the Pliensbachian–Toarcian transition of the Llanbedr (Mochras Farm) core in Wales and Bou Oumardoul n'Imazighn section in Morocco shows that the onset of the environmental perturbations is associated with a positive carbon isotope excursion spanning the Pliensbachian/Toarcian boundary. This is followed by a negative carbon isotope excursion during the earliest Toarcian that coincides with the global collapse of neritic carbonate factory and an ample sea-level fall.
