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Latest Triassic onset of the Central Atlantic Magmatic Province (CAMP) volcanism in the Fundy Basin (Nova Scotia): New stratigraphic constraints
Abstract
In this paper we investigate the stratigraphic relationship between the emplacement of the CAMP basalts and the Triassic–Jurassic (Tr–J) boundary in the Fundy Basin (Nova Scotia, Canada). This is one of the best exposed of the synrift basins of eastern North America (ENA) formed as a consequence of the rifting that led to the formation of the Atlantic Ocean. The Triassic palynological assemblages found in the sedimentary rocks below (uppermost Blomidon Formation) and just above the North Mountain Basalt (Scots Bay Member of the McCoy Brook Formation) indicate that CAMP volcanism, at least in Nova Scotia, is entirely of Triassic age, occurred in a very short time span, and may have triggered the T–J boundary biotic and environmental crisis. The palynological assemblage from the Blomidon Formation is characterised by the dominance of the Circumpolles group (e.g. Gliscopollis meyeriana, Corollina murphyae, Classopollis torosus) which crosses the previously established Tr–J boundary. The Triassic species Patinasporites densus disappears several centimetres below the base of the North Mountain basalt, near the previously interpreted Tr–J boundary. The lower strata of the Scots Bay Member yielded a palynological assemblage dominated by Triassic bisaccate pollens (e.g Lunatisporites acutus, L. rhaeticus Lueckisporites sp., Alisporites parvus) with minor specimens of the Circumpolles group. Examination of the state of preservation and thermal alteration of organic matter associated with the microfloral assemblages precludes the possibility of recycling of the Triassic sporomorphs from the older strata. Our data argue against the previous definition of the Tr–J boundary in the ENA basins, which was based mainly on the last occurrence of P. densus. Consequently, it follows that the late Triassic magnetostratigraphic correlations should be revised considering that chron E23r, which is correlated with the last occurrence of P. densus in the Newark basin, does not occur at the Tr–J boundary but marks rather a late Triassic (probably Rhaetian) reversal.
... sugerindo um segundo episódio de stress ambiental na bacia. Este segundo evento pode estar associado à influência do PMAC do Nordeste da América (Whiteside et al., , 2010Cirilli et al., 2009). Porcellispora longdonensis e os pólenes Alisporites sp., Perinopollenites elatoides e Pinuspollenites minimus. ...
... or after the Triassic-Jurassic Boundary . Palynological studies have shown 6 that CAMP volcanism started before the TJB and, thus, corroborating the hypothesis of these eruptions possibly having an influence on the biotic crisis of this limit (Marzoli et al., 2008;Cirilli et al., 2009;Cirilli, 2010 have allowed the Lusitanian Basin to be divided into three distinct sub-basins separated by large regional faults (Kullberg et al., 2013). The first is the Septentrional sector, which is limited to the south by the Nazaré Fault. ...
... Ma; Gradstein and Ogg, 2020) since it represents one of the most severe biotic crises of the Phanerozoic (Raup and Sepkoski, 1982;Sepkoski, 1996;Tanner et al., 2004). The end-Triassic extinction caused a faunal turnover Van de Schootbrugge et al., 2009;Lindström et al., 2017aLindström et al., , 2017b, particularly among marine invertebrates (Guex et al., 2004;Van de Schootbrugge et al., 2008), but the impact on terrestrial floras is debatable (Tanner et al., 2004;Cirilli et al., 2009;Cirilli, 2010;Lucas et al., 2011). Recent studies of European plant macro-and microfloral databases suggest that no major extinction occurred across the TJB (Barbacka et al., 2017). ...
The biostratigraphy of the Lusitanian and Algarve basins is based on macrofossils and microfossils (foraminifers, nannofossils, and ostracods). Compared to these works, palynological studies are rare in these basins. Palynomorphs are a powerful biostratigraphic and paleoenvironmental tool, and their research could significantly contribute to the context of the two basins. In this project, the Upper Triassic and Lower Jurassic of the Lusitanian and Algarve basins were studied.
In the Lusitanian Basin, twelve sections were sampled, all in Coimbra and Miranda do Corvo: Lamas I, Lamas II, Castelo Viegas I, Castelo Viegas II, IdealMed, Alto de São João, Parque de Campismo, Sobral Cid, Carvalhais, Redonda, Lordemão and Eiras. A total of 122 samples were collected in these sections and studied in detail.
In the Algarve Basin, fifteen sections were sampled throughout the entire basin: Vale de Fuzeiros, Bengado, International Racetrack of Algarve, Marco, Loulé Rock Salt Mine, Santa Rita, Amorosa, Amado’s Beach, Rocha da Pena, Bodega, Barragem do Funcho, Santa Catarina Fonte do Bispo, Fonte da Pedra, Diapiro de Albufeira and Ayamonte. Full amount of 254 samples were collected in these sections and studied in detail.
Six boreholes were sampled: Golfinho-1, Santiago do Cacém-3, Santiago do Cacém-42, Santiago do Cacém-61, Campelos-1, and Lula-1, performing 122 samples collected from these boreholes and studied in detail.
The data obtained in the Lusitanian Basin allowed improving the dating of the units of the Silves Group, from the oldest to the most recent: Conraria Formation, Penela Formation, Castelo Viegas Formation, and Pereiros Formation.
The co-occurrence of typical Norian and Rhaetian palynomorphs, such as Classopollis meyerianus, Granuloperculatipollis rudis, Patinasporites densus, Vallasporites ignacii, Duplicisporites granulatus, Paracirculina quadruplicis, and Praecirculina granifer, allowed the Conraria Formation, at the base of the Silves Group, to be dated from the Norian to lower Rhaetian. Based on the palynological content, proposing the informal Classopollis meyerianus-Granuloperculatipollis rudis palynozone for the Conraria Formation was possible.
Two informal palynozones are proposed for the Pereiros Formation: Ischyosporites variegatus-Kraeuselisporites reissingeri and Pinuspollenites minimus. The informal palynozone Ischyosporites-variegatus-Kraeuselisporites reissingeri is associated with the upper Rhaetian due to the presence of Classopollis meyerianus, Classopollis torosus together with index species of this age, such as Ischyosporites variegatus, Kraeuselisporites reissingeri, and Rhaetipollis germanicus. The informal palynozone Pinuspollenites minimus is defined based in the first occurrence of Pinuspollenites minimus and Perinopollenites elatoides, accompanied by the dominance of Classopollis meyerianus and Classopollis torosus, dating from the base of the Hettangian.
Therefore, based on the palynological association obtained in these two informal
palynozones, it is possible to date the Pereiros Formation as being upper Rhaetian to lower Hettangian and conclude that the Triassic-Jurassic transition occurs at the base of this formation within the informal Ischyosporites variegatus-Kraeuselisporites reissingeri palynozone. tener, Ischyosporites variegatus, Kraeuselisporites reissingeri, and Porcellispora longdonensis, and the pollen grains Alisporites sp., Perinopollenites elatoides, and Pinuspollenites minimus, allowed confirming the Hettangian age for the base of this formation. The presence of foraminiferal linings in the basal part of the Pereiros Formation documents, the first marine incursion event that occurred in the Lusitanian Basin. These data allow us to interpret this unit as deposited in an estuary environment and suggest a small marine transgression episode. The middle part of this formation is interpreted as a coastal plain environment dominated by fluvial sedimentation processes recording a small marine regression episode, and the top of Pereiros Formation as an evaporite tidal flat under hot, arid climatic conditions.
In the Algarve Basin, the Silves Group comprehends the units, from the oldest to the most recent: São Bartolomeu de Messines Clays, Silves Sandstones, Silves Marl-Carbonate Evaporitic Complex, and Volcano-Sedimentary Series.
For the first time, it is possible to associate an age interval with the Silves Group, ranging from the early Carnian to the early Hettangian, based on palynomorphs, including the Triassic-Jurassic transition, and to establish paleoenvironmental interpretations.
The most basal part of the Silves Sandstones was sampled, and its palynological association, which comprised Aulisporites astigmosus, Enzonalasporites vigens, Vallasporites ignacii, and Samaropollenites minimus, allowed the base of this unit to be dated as early Carnian. These data will enable us to interpret that the beginning of sedimentation in the Algarve Basin occurred in the Late Triassic (early Carnian). The co-occurrence of taxa such as Aulisporites astigmosus, Enzonalasporites vigens, Samaropollenites specious and Tulesporites briscoensis (recorded for the first time in Iberia and Europe) indicates a mixture of microfloras with affinities from Central Europe and North America, in the Carnian, this data is consistent with the paleogeographic position of the Iberian Peninsula during the Late Triassic. The new palynological data from this investigation indicate that the top of the Silves Sandstones unit dates from the late Carnian, the base of the Silves Marl-Carbonate Evaporitic Complex unit dates from the late Carnian and the top of this last unit dates from the late Rhaetian to the early Hettangian. From a paleoenvironmental point of view, the presence and rapid increase of algal spores (Plaesiodictyon mosellanum ssp. variable, Plaesiodictyon mosellanum ssp. bullatum, Botryococcus spp., and Ovoidites sp.) at the base of the Silves Marl-Carbonate Evaporitic Complex unit indicates the transition from alluvial depositional systems (Silves Sandstones) initially, to lacustrine environments, which later changed to arid coastlines. The consistent increase in xerophytic elements (e.g., pollens grains Alisporites spp., Classopollis spp., Cerebropollenites spp., and Perinopollenites spp.) indicates a shift to more arid and hot conditions for the top of the Silves Group, being consistent with lithofacies deposited in sabkha environment (evaporites).
For the first time, the Triassic-Jurassic transition is described based in palynomorph studies in the Algarve Basin at the top of the Silves Marl-Carbonate Evaporitic Complex in the Loulé Rock Salt Mine. The previous transition occurs in a mudstone layer, with ca. 1 m thick, interspersed with evaporites, and should correspond to a short period of interruption of the evaporite environment. With this work, we propose an age of the Silves Group in the Lusitanian Basin, from the Norian – early Hettangian, and in the Algarve Basin from the lower Carnian to the early Hettangian, with the identification, for the first time, of the Triassic-Jurassic transition in Portugal.
The new lithostratigraphic schemes of the Silves Group for the Lusitanian and Algarve basins, together with the paleoenvironmental interpretations obtained with this investigation, are a significant contribution to the context of the Late Triassic and Early Jurassic in Portugal, especially for biostratigraphy. The absence of palynological data from the Penela and Castelo Viegas formations due to not favorable lithologies to palynological studies did not allow for a review and improvement in the precision of the age associated with these formations. However, considering their stratigraphic position, sandwiched between the Conraria Formation (Norian – early Rhaetian) and the Pereiros Formation (late Rhaetian – earliest Hettangian), these formations would date, indirectly, from the Rhaetian.
In conclusion, the palynological associations obtained in the Lusitanian Basin made it possible to date the formations of the Silves Group from the Norian to the Hettangian.
To identify the limit between the Triassic and Jurassic in the Lusitanian Basin, new samples were collected in the most basal part of the Pereiros Formation. The palynological content obtained, such as the spores Calamospora tener, Ischyosporites variegatus, Kraeuselisporites reissingeri, and Porcellispora longdonensis, and the pollen grains Alisporites sp., Perinopollenites elatoides, and Pinuspollenites minimus, allowed confirming the Hettangian age for the base of this formation. The presence of foraminiferal linings in the basal part of the Pereiros Formation documents, the first marine incursion event that occurred in the Lusitanian Basin. These data allow us to interpret this unit as deposited in an estuary environment and suggest a small marine transgression episode. The middle part of this formation is interpreted as a coastal plain environment dominated by fluvial sedimentation processes recording a small marine regression episode, and the top of Pereiros Formation as an evaporite tidal flat under hot, arid climatic conditions.
In the Algarve Basin, the Silves Group comprehends the units, from the oldest to the most recent: São Bartolomeu de Messines Clays, Silves Sandstones, Silves Marl-Carbonate Evaporitic Complex, and Volcano-Sedimentary Series.
For the first time, it is possible to associate an age interval with the Silves Group, ranging from the early Carnian to the early Hettangian, based on palynomorphs, including the Triassic-Jurassic transition, and to establish paleoenvironmental interpretations. The most basal part of the Silves Sandstones was sampled, and its
palynological association, which comprised Aulisporites astigmosus, Enzonalasporites vigens, Vallasporites ignacii, and Samaropollenites minimus, allowed the base of this unit to be dated as early Carnian. These data will enable us to interpret that the beginning of sedimentation in the Algarve Basin occurred in the Late Triassic (early Carnian). The co-occurrence of taxa such as Aulisporites astigmosus, Enzonalasporites vigens, Samaropollenites speciosus and Tulesporites briscoensis (recorded for the first time in Iberia and Europe) indicates a mixture of microfloras with affinities from Central Europe and North America, in the Carnian, this data is consistent with the paleogeographic position of the Iberian Peninsula during the Late Triassic.
The new palynological data from this investigation indicate that the top of the Silves Sandstones unit dates from the late Carnian, the base of the Silves Marl-Carbonate Evaporitic Complex unit dates from the late Carnian and the top of this last unit dates from the late Rhaetian to the early Hettangian. From a paleoenvironmental point of view, the presence and rapid increase of algal spores (Plaesiodictyon mosellanum ssp. variable, Plaesiodictyon mosellanum ssp. bullatum, Botryococcus spp., and Ovoidites sp.) at the base of the Silves Marl-Carbonate Evaporitic Complex unit indicates the transition from alluvial depositional systems (Silves Sandstones) initially, to lacustrine environments, which later changed to arid coastlines. The consistent increase in xerophytic elements (e.g., pollens grains Alisporites spp., Classopollis spp., Cerebropollenites spp., and Perinopollenites spp.) indicates a shift to more arid and hot conditions for the top of the Silves Group, being consistent with lithofacies deposited in sabkha environment (evaporites).
For the first time, the Triassic-Jurassic transition is described based in palynomorph studies in the Algarve Basin at the top of the Silves Marl-Carbonate Evaporitic Complex in the Loulé Rock Salt Mine. The previous transition occurs in a mudstone layer, with ca. 1 m thick, interspersed with evaporites, and should correspond to a short period of interruption of the evaporite environment.
With this work, we propose an age of the Silves Group in the Lusitanian Basin, from the Norian – early Hettangian, and in the Algarve Basin from the lower Carnian to the early Hettangian, with the identification, for the first time, of the Triassic-Jurassic transition in Portugal.
The new lithostratigraphic schemes of the Silves Group for the Lusitanian and Algarve basins, together with the paleoenvironmental interpretations obtained with this investigation, are a significant contribution to the context of the Late Triassic and Early Jurassic in Portugal, especially for biostratigraphy.
... Ma; Gradstein and Ogg, 2020) since it represents one of the most severe biotic crises of the Phanerozoic (Raup and Sepkoski, 1982;Sepkoski, 1996;Tanner et al., 2004). The end-Triassic extinction caused a faunal turnover Van de Schootbrugge et al., 2009;Lindström et al., 2017aLindström et al., , 2017b, particularly among marine invertebrates (Guex et al., 2004;Van de Schootbrugge et al., 2008), but the impact on terrestrial floras is debatable (Tanner et al., 2004;Cirilli et al., 2009;Cirilli, 2010;Lucas et al., 2011). Recent studies of European plant macro-and microfloral databases suggest that no major extinction occurred across the TJB (Barbacka et al., 2017). ...
... With the exception of the southernmost part of the Lusitanian Basin (West Portugal; Azerêdo et al., 2003;Kullberg et al., 2013) there is no direct evidence of CAMP related rocks. The CAMP magmatism contributed to global environmental and climatic changes, increasing the effects of the end-Triassic extinction phase Cirilli et al., 2009;Deenen et al., 2010;Capriolo et al., 2020). The flora of this age may have been affected by the effects of CAMP volcanism, with acid rain and acidification of freshwater, and global warming due to the greenhouse effect (Hesselbo et al., 2002;Guex et al., 2004;Marzoli et al., 2004;Tanner et al., 2004Tanner et al., , 2007Schaltegger et al., 2008;Van de Schootbrugge et al., 2008Cirilli et al., 2009Cirilli et al., , 2018Lindström, 2016;Davies et al., 2017;Lindström et al., 2019;Panfili et al., 2019). ...
... The CAMP magmatism contributed to global environmental and climatic changes, increasing the effects of the end-Triassic extinction phase Cirilli et al., 2009;Deenen et al., 2010;Capriolo et al., 2020). The flora of this age may have been affected by the effects of CAMP volcanism, with acid rain and acidification of freshwater, and global warming due to the greenhouse effect (Hesselbo et al., 2002;Guex et al., 2004;Marzoli et al., 2004;Tanner et al., 2004Tanner et al., , 2007Schaltegger et al., 2008;Van de Schootbrugge et al., 2008Cirilli et al., 2009Cirilli et al., , 2018Lindström, 2016;Davies et al., 2017;Lindström et al., 2019;Panfili et al., 2019). ...
New evidence is presented on the Triassic–Jurassic boundary in the northern Lusitanian Basin, Portugal, based on miospore assemblages from a composite Upper Triassic to Lower Jurassic succession of the Silves Group. The latter comprises, from base to top, the Conraria, Penela, Castelo Viegas and the Pereiros formations. Three informal palynological zones have been documented and compared with coeval palynozones from West and South Europe providing new biostratigraphic data to detail the age of the lower and upper formations of the Silves Group and to review previous age attribution.
A Norian, possibly earliest Rhaetian age, is documented for the Conraria Formation on the basis of a palynological assemblage referable to the Classopollis meyerianus–Granuloperculatipollis rudis (CG) zone. The Penela and Castelo Viegas formations did not allow a palynostratigraphic revision, due to the not promising lithology for palynological studies. The Pereiros Formation is dated on the basis of microflora assemblages referable, from bottom to top, the Ischyosporites variegatus–Kraeuselisporites reissingeri (IK) zone of late Rhaetian–earliest Hettangian age and Pinuspollenites minimus (Pm) zone of Hettangian age. The discontinuity between the underlying Castelo Viegas Formation and the overlying Pereiros Formation did not allow to define the lower boundary of the IK palynozone. The Triassic–Jurassic boundary lies in the lower part of Pereiros Formation within the IK zone. The microflora assemblages from the Lusitanian Basin show close affinity to those of eastern N America and western Tethys areas.
... The less sampled skeletal record is consistent with the footprints (Olsen et al., 2002). Palynological and tetrapod data of the other CAM basins are consistent though less studied (Cornet, 1977;Olsen et al., 2002;Cirilli et al., 2009;. Both in sporomorphs and footprints, little discernable change exists at the supraspecies level above the zone of concentrated biotic change of the ETE, except for the addition of ornithischian and prosauropod skeletal remains and footprints in the Hartford and Fundy basins . ...
... Sections in the Fundy Basin (see Figs. 12.1,12.4,12.6) have well-studied sporomorph assemblages below the CAMP (North Mountain) basalt (Fowell & Traverse, 1995;Cirilli et al., 2009), paleomagnetic polarity chron E23r (Deenen et al., 2011), and a well-characterized vertebrate assemblage directly above the basalt described by Olsen et al. (1987), Sues and Olsen (2015), and Fedak et al. (2015). ...
... (NA) from Tanner et al., 2008) was at Partridge Island (see Fig. 12.4b). Sporomorph assemblages recovered from three sampling efforts (Fowell & Traverse, 1995;Whiteside et al., 2007;Cirilli et al., 2009) produced identical results. Preservation was good (except in red strata), although the grains were dark, Circumpolles group species dominated (e.g., Classopollis spp.), and the stratigraphically highest samples consistently lack vesicate forms (e.g., Patinasporites densus). ...
Multiple lines of evidence suggest that volcanic and thermogenic gas emanations from the voluminous eruptions of the Central Atlantic Magmatic Province (CAMP) triggered the end‐Triassic mass extinction. However, a comparison of the timing and duration of the biotic and environmental crises with the timing and duration of the magmatic activity is difficult with existing data, especially when comparing the sedimentary archives below radioisotopically dated CAMP lavas. Here, we report multiple iridium anomalies interpreted to be the remnants of weathered basaltic ashes or aerosols of CAMP eruptions from three basins across a 15° swath of paleolatitude. Milankovitch‐controlled climate cycles pace the lacustrine strata of these basins, and in conjunction with paleomagnetic reversal stratigraphy and abundant palynological data, allow us to constrain the timing of magmatic events to be coincident with the extinctions. Thus, platinum group element concentrations provide geochemical traces of CAMP eruptions and can serve as potential proxies for CAMP eruptive pulses in both marine and nonmarine Triassic‐Jurassic boundary successions, permitting evaluation of correlations worldwide.
... Preserved lava flows are relatively rare and are presently restricted to Triassic-Jurassic continental sedimentary basins, e.g., in Portugal, Canada, USA, Morocco, Algeria, Brazil and Bolivia Vérati et al., 2007;Martins et al., 2008;Bertrand et al., 2014;Callegaro et al., 2014a;Merle et al., 2011Merle et al., , 2014Marzoli et al., 2019;Tegner et al., 2020a), where the volcanic piles do not exceed 500 m of cumulative thickness. CAMP lavas were mostly erupted sub-aerially or occasionally within shallow lakes or lagoons and are intercalated with sediments ranging in age from Rhaetian to Hettangian (Youbi et al., 2003;Marzoli et al., 2004Marzoli et al., , 2019Cirilli et al., 2009;Panfili et al., 2019). Preserved pyroclastic (e.g., tuffs) CAMP rocks are extremely rare, which is quite anomalous compared to other large igneous provinces (Ross et al., 2005;White et al., 2009). ...
... Kürschner and Herngreen, 2010; Fig. 3). Similar assemblages have also been recovered below the oldest flows in Eastern North America, i.e. below the North Mountain Basalt and the Orange Mountain Basalt of the Prevalent group of the Newark Basin (Fowell et al., 1993;Cirilli et al., 2009). In Morocco, Upper flows of the Prevalent group are capped by sediments containing a palynological assemblage indicating a Rhaetian age, as it includes specimens of Patinasporites densus (Panfili et al., 2019). ...
... According to some authors (e.g., Blackburn et al., 2013), this palynological turnover marks the end-Triassic extinction event in the Newark Basin. However, a latest Triassic palynological assemblage was recorded in sediments outcropping on top of the CAMP lava pile in Nova Scotia suggesting that the Canadian CAMP volcanism also occurred mostly within the topmost Triassic (Cirilli et al., 2009). ...
The end-Triassic mass extinction (ETME) is thought to have been caused by voluminous, pulsed volcanic activity of the Central Atlantic Magmatic Province (CAMP). Over the last decades, various geochemical signals and proxy records, including δ13C, pCO2, iridium and other platinum-group elements, mercury, polycyclic aromatic hydrocarbons (PAH), charcoal and SO2, have been directly or indirectly attributed to CAMP magmatism. Here, we compile these various records in a stratigraphic framework to present a cohesive chain of events for the CAMP and the end-Triassic mass extinction. Mercury and iridium anomalies in sediments indicate that CAMP activity commenced prior to the onset of the marine extinctions (as marked by the last occurrence of the Triassic ammonoid Choristoceras marshi or closely related species), and a negative δ13C excursion in organic matter (the Marshi CIE). This CIE may be explained by input of light carbon to the atmosphere from CAMP lavas of the Tiourjdal and Prevalent groups. Pedogenic carbonate below and above the Prevalent group in North America indicates a more than twofold increase in atmospheric pCO2. Subsequent n-alkane C-isotopes, and stomatal pCO2 data seem to indicate a temporary cooling after the Marshi CIE, which is consistent with climate models incorporating volcanic emissions of both CO2 and SO2. Records of excess iridium and Hg/TOC indicate intensified magmatism during the extinction interval. Tectonic and perhaps epeirogenic (i.e. doming due to rise of magma) activity is suggested by the occurrence of multiple and widespread seismites in Europe. Atmospheric pCO2 proxies indicate global warming, which culminated contemporaneously with the Spelae CIE. Global warming is corroborated by increased wildfire activity testified by charcoal and pyrolytic PAH records. Increased isotopic ratios of Os and Sr from sections that record global ocean signatures suggest increased weathering of continental crust likely due to climatic changes. Just prior to the increase in pCO2 from stomatal proxy data, fossil plants exhibit SO2-induced damage indicating excess sulfur dioxide deposition priot to and across the Triassic–Jurassic boundary. At the same time, increased ratios of heavy molecular PAHs (coronene/benzo(a)pyrene) in sediments suggest metamorphism of organic sediments also occurred across the Triassic–Jurassic boundary. These proxies may suggest that thermogenic release of light carbon and sulfur from sill intrusions in the Trans-Amazonian basins, where both evaporate- and organic-rich sediments are known to have been intruded, may have played an important role during the course of the ETME. Geochemical traces of magmatism, i.e. Ir and Hg, appear to have gradually disappeared during the Hettangian, suggesting that later phases of CAMP were less voluminous. Stomatal proxy data from Greenland and n-alkane C-isotope data from the UK, together with oxygen isotope data from carbonate fossils in the UK, may indicate that the global warming at the Spelae CIE was succeeded by another short-term cooling event. A gradual decrease in δ13C culminated at the top-Tilmanni CIE, marking the beginning of a long-term steady state with more negative C-isotope values than prior to the ETME. At this time, terrestrial ecosystems appear to have stabilized globally and ammonoids had begun to rediversify.
... CAMP-related igneous activity included the intrusion of diabase sheets and dikes and the eruption of basalts. In the region surrounding the Orpheus basin ( Fig. 1a), CAMP-related igneous rocks include the North Mountain Basalt in the Fundy rift basin (Dostal and Greenough, 1992;Olsen and Et-Touhami, 2008;Cirilli et al., 2009; and the Shelburne (Pe-Piper et al., 1992;Dostal and Durning, 1998;Dunn et al., 1998), Caraquet (Pe-Piper et al., 1992Dostal and Durning, 1998), and Avalon dikes (Pe-Piper et al., 1992). CAMP-related basalts are also present in nearby wells in the region between the Fundy and Orpheus rift basins (White et al., 2017), and CAMP-related basalts have been encountered in wells and seismically imaged in the Mohican rift basin on the Scotian Shelf (e.g., Weston et al., 2012;Deptuck and Altheim, 2018) and in the Jeanne d'Arc rift basin of the Grand Banks region (Pe-Piper et al., 1992). ...
... reports of CAMP-related igneous rocks in the region surrounding the Orpheus rift basin (e.g., Dostal and Greenough, 1992;McHone, 1992;Pe-Piper et al., 1992;Dostal and Durning, 1998;Cirilli et al., 2009;Jourdan et al., 2009), we propose that many of these igneous sheets are associated with CAMP, which as discussed previously, is a major igneous province that formed in latest Triassic to earliest Jurassic time (McHone, 1992;Pe-Piper et al., 1992;Olsen et al., 2003;Marzoli et al., 2011;Blackburn et al., 2013;Davies et al., 2017;Marzoli et al., 2018;Marzoli et al., 2019). It is possible that some igneous sheets, not truncated by the breakup unconformity, are associated with Early Cretaceous magmatic activity as, for example, reported by Zulfitriadi (2011). ...
The salt-rich Orpheus rift basin, part of the eastern North American (ENAM) rift system, formed during the Late Triassic to Early Jurassic prior to opening of the Atlantic Ocean. Using a dense grid of 2D seismic-reflection lines, data from nearby wells, and information from adjacent ENAM rift basins, we have established a tectonostratigraphic framework, identified key structural elements, and reconstructed the deformation history for the eastern part of the basin. Our work shows that a series of E-striking, S-dipping faults with normal separation bound the basin on the north. Deformation within the basin is complex with fault-propagation folds above deep-seated, intrabasin faults, detachment folds, detached thrust faults, and salt diapirs. The synrift salt consists of a lower massive unit that underlies a younger unit with two distinct interfingering facies. Facies A, consisting of salt and interbedded sedimentary rocks (likely shales), developed near the border-fault system and its relay ramps. Facies B, consisting of massive salt with few interbedded sedimentary rocks, developed within the basin center. The youngest synrift unit accumulated exclusively within minibasins near the northern border-fault system. Based on location, this unit likely consists of coarse-grained and poorly sorted alluvial-fan or talus-slope deposits shed from the footwall. All synrift units are intruded by igneous sheets likely associated with the Central Atlantic Magmatic Province and, thus, are mostly Late Triassic (or possibly older). The border-fault system profoundly affected deposition within the eastern Orpheus rift basin by providing pathways for clastic sediment input into the salt-rich basin. These depositional patterns subsequently influenced deformation associated with lateral salt flow during minibasin formation. In regions with interbedded salt, detachment folds and thrust faults developed, whereas salt walls and columns developed in regions with more massive salt.
... CAMP-related igneous activity included the intrusion of diabase sheets and dikes and the eruption of basalts. In the region surrounding the Orpheus basin (Fig. 1a), CAMP-related igneous rocks include the North Mountain Basalt in the Fundy rift basin (Dostal and Greenough, 1992;Olsen and Et-Touhami, 2008;Cirilli et al., 2009;Jourdan et al., 2009) and the Shelburne (Pe-Piper et al., 1992;Dostal and Durning, 1998;Dunn et al., 1998), Caraquet (Pe-Piper et al., 1992;Dostal and Durning, 1998), and Avalon dikes (Pe-Piper et al., 1992). CAMP-related basalts are also present in nearby wells in the region between the Fundy and Orpheus rift basins (White et al., 2017), and CAMP-related basalts have been encountered in wells and seismically imaged in the Mohican rift basin on the Scotian Shelf (e.g., Weston et al., 2012;Deptuck and Altheim, 2018) and in the Jeanne d'Arc rift basin of the Grand Banks region (Pe-Piper et al., 1992). ...
... Because the breakup unconformity separates the synrift strata from the overlying late Middle Jurassic postrift strata (OETR, 2014), magmatic activity must have occurred during and/or after the Late Triassic and during and/or before the late Middle Jurassic. Based on this time interval as well as the numerous reports of CAMP-related igneous rocks in the region surrounding the Orpheus rift basin (e.g., Dostal and Greenough, 1992;McHone, 1992;Pe-Piper et al., 1992;Dostal and Durning, 1998;Cirilli et al., 2009;Jourdan et al., 2009), we propose that many of these igneous sheets are associated with CAMP, which as discussed previously, is a major igneous province that formed in latest Triassic to earliest Jurassic time (McHone, 1992;Pe-Piper et al., 1992;Olsen et al., 2003;Marzoli et al., 2011Marzoli et al., , 2018Marzoli et al., , 2019Blackburn et al., 2013;Davies et al., 2017). It is possible that some igneous sheets, not truncated by the breakup unconformity, are associated with Early Cretaceous magmatic activity as, for example, reported by Zulfitriadi (2011). ...
The salt-rich Orpheus rift basin, part of the eastern North American (ENAM) rift system, formed during the Late Triassic to Early Jurassic prior to opening of the Atlantic Ocean. Using a dense grid of 2D seismic-reflection lines, data from nearby wells, and information from adjacent ENAM rift basins, we have established a tectonostratigraphic framework, identified key structural elements, and reconstructed the deformation history for the eastern part of the basin. Our work shows that a series of E-striking, S-dipping faults with normal separation bound the basin on the north. Deformation within the basin is complex with forced folds above deep-seated intrabasin faults, detachment folds, detached thrust faults, and salt diapirs. The synrift evaporite sequence consists of an older massive salt unit that underlies a younger unit with two distinct interfingering facies. Facies A, consisting of salt and interbedded sedimentary rocks (likely shales), developed near the border-fault system and its relay ramps. Facies B, consisting of massive salt with few interbedded sedimentary rocks, developed toward the basin center. The youngest synrift unit accumulated exclusively within minibasins near the northern border-fault system. Based on location, this youngest synrift unit likely consists of coarse-grained and poorly sorted alluvial-fan or talus-slope deposits shed from the footwall. All synrift units are intruded by igneous sheets likely associated with the Central Atlantic Magmatic Province and, thus, are mostly Late Triassic in age (or possibly older). The border-fault system profoundly affected deposition within the eastern Orpheus rift basin by providing pathways for clastic sediment input into the salt-rich basin. These depositional patterns subsequently influenced deformation associated with lateral salt flow during minibasin formation. In regions with interbedded salt, detachment folds and thrust faults developed, whereas salt walls and stocks developed in regions with more massive salt.
... In recent years, the focus of attention in the study of the end-Triassic extinctions has been the environmental effects of the eruption of the flood basalts of the Central Atlantic Magmatic Province (CAMP). It is now well-established that the products of the CAMP eruptions span the system boundary [6][7][8][9] , with the majority of the total lava volume ejected during an initial eruptive episode prior to the paleontologically-defined TJB 10,11 . Within the basins of the Newark Supergroup, the eruptions proceeded in three main episodes, separated by eruptive hiatuses during which sediments accumulated, across a total interval of ca. ...
... These new data, combined with previous data from the Fundy and western Newark basins 30,31,35,36 , suggest the potential presence of a widespread, correlative, Ir-enriched horizon below the base of the oldest CAMP flow in the Newark basins. All of the horizons of elevated Ir that lie below the oldest CAMP flows share similar palynological assemblages, the so-called fern spikes, and common macrofloral elements 8,48,49 . However, horizons in the Deerfield basin, in the basal Fall River Beds (5.0 m below the DB), and in the Hartford basin at the Silver Ridge locality, that appear to correlate palynologically with this horizon showed no Ir enrichment. ...
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.
... The observed negative carbon-isotope excursion (CIE) at the end-Triassic mass extinction directly predated the onset of CAMP basalt eruptive flows in the Fundy, Newark and Hartford Basins (North America; Cirilli et al., 2009;Whiteside et al., 2010), but coincided with the onset of CAMP basalt emplacement in the Argana Basin and High Atlas Mountains (Morocco; Deenen et al., 2010;Dal Corso et al., 2014; see also a review by Korte et al., 2019 and references therein;Panfili et al., 2019). The onset of eruption of the major CAMP basalt flows at the time of the end-Triassic mass extinction was, however, likely preceded by intrusions of major dykes and sills, feeding the oldest basalt extrusives, up to~100 kyr earlier (Marzoli et al., 2011;Dal Corso et al., 2014;Davies et al., 2017;Panfili et al., 2019). ...
... The atmospheric flux of humidity from the oceans into continental interiors, and associated precipitation and plant growth are, however, likely to have been much more common along the eastern margin of Pangaea, with wetter conditions and lush vegetation along most of the north-western Tethyan realm (Rees et al., 2000;Barrón et al., 2006;Valdes, 2006, 2008;Gómez et al., 2007;McElwain et al., 2007;Bonis et al., 2009;Cirilli et al., 2009;van de Schootbrugge et al., 2009;Bonis and Kürschner, 2012;Lindström et al., 2012;Pienkowski et al., 2014;Cirilli et al., 2018). ...
... One sample was collected at the base of the CAMP lava flows on Grand Manan Island (44°45′24″ North, 66°50′ 08″ West; New Brunswick, Canada). This sample is stratigraphically equivalent to the siltstones cropping out at the base of the North Mountain Basalt in Nova Scotia, Bay of Fundy (Partridge Island; Cirilli et al., 2009;Fowell and Traverse, 1995;Kontak, 2008;McHone, 2011). ...
... One sample (BH20 , Table S1) was collected at the base of the lowest CAMP lava flow on Grand Manan Island (Figs. 1F, 2; McHone, 2011) and is stratigraphically similar to the sedimentary rocks outcropping at the base of the North Mt. Basalts at Partridge Island, Nova Scotia (e.g., Cirilli et al., 2009). Eighty-six zircon grains from this sample yielded Concordia ages. ...
The complex history of assemblage and disruption of continental plates surrounding the Atlantic Ocean is in part recorded by the distribution of detrital zircon ages entrained in continental sedimentary strata from Morocco (Central High Atlas and Argana basins) and Canada (Grand Manan Island, New Brunswick). Here we investigate detrital zircon from the latest Triassic (ca. 202 Ma) sedimentary strata directly underlying lava flows of the Central Atlantic magmatic province or interlayered within them. SHRIMP (Sensitive High-Resolution Ion Microprobe) and LA-ICP-MS (Laser Ablation–Inductively Coupled Plasma–Mass Spectrometry) U–Pb ages for zircon range from Paleozoic to Archean with a dominant Neoproterozoic peak, and significant amounts of ca. 2 Ga zircon. These ages suggest a prevailing West African (Gondwanan) provenance at all sampling sites. Notably, the Paleoproterozoic zircon population is particularly abundant in central Morocco, north of the High Atlas chain, suggesting the presence of Eburnean-aged rocks in this part of the country, which is consistent with recent geochronologic data from outcropping rocks. Minor amounts of late Mesoproterozoic and early Neoproterozoic zircon (ca. 1.1–0.9 Ga) in Moroccan samples are more difficult to interpret. A provenance from Avalonia or Amazonia, as proposed by previous studies is not supported by the age distributions observed here. An involvement of more distal source regions, possibly located in north-eastern Africa (Arabian Nubian Shield) would instead be possible. Paleozoic zircon ages are abundant in the Canadian sample, pointing to a significant contribution from Hercynian aged source rocks. Such a signal is nearly absent in the Moroccan samples, suggesting that zircon-bearing Hercynian granitic rocks of the Moroccan Meseta block were not yet outcropping at ca. 200 Ma. The only Moroccan samples that yield Paleozoic zircon ages are those interlayered within the CAMP lavas, suggesting an increased dismantling (i.e. uplift) of the Hercynian chain during emplacement of CAMP lava flows, combined with subsidence of the volcanic grabens.
... Correlation based on ammonite bio-and palyno-stratigraphy, including the δ 13 C org records for each locality, along the transect shown on Fig. 1. P. densus and Vallasporites ignacii instead indicate an early Rhaetian age, or older, following the known last appearance datums in NW Europe of these pollen taxa (Van Veen, 1995;Marzoli et al., 2004Marzoli et al., , 2008Cirilli et al., 2009). In addition, several authors have also argued that an increase in fern spores, a spore spike, just below the oldest CAMP basalts would mark the end-Triassic event, similar to the spore spike recorded after the end-Cretaceous mass extinction (Olsen et al., 2002;Whiteside et al., 2010;Vajda et al., 2001). ...
... Simplified relative sea-level curve for NW Europe and composite C-isotope curve based on the reviewed records herein. Stratigraphic range for Patinasporites densus/Enzonalasporites spp. in Morocco and eastern North America (E.N.A.) after Fowell and Olsen (1993), Olsen et al. (2002), Whiteside et al. (2007Whiteside et al. ( , 2008, Cirilli et al. (2009), Marzoli et al. (2011. CAMP U-Pb ages are from Blackburn et al. (2013), with the exception of the age for the North Mountain Basalt marked with *, which is from Schoene 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.
... It seems plausible to hypothesize a loss of endothermy around the boundary between the Triassic and the Jurassic. It is generally assumed that the ETME is one of the five greatest extinction events recorded (Barnosky et al., 2011;Raup & Sepkoski, 1982), although the causes of this event are still unclear, potentially implying a meteoric impact (while it is still debated, see Onoue et al., 2012Onoue et al., , 2016, volcanic eruptions (Cirilli et al., 2009;Kozur & Bachmann, 2005;Kozur & Weems, 2007, or potentially not a single event but a succession of smaller and more local crises (Lucas & Tanner, 2015). Whatever the causes and the succession of events were, all non-crocodylomorph pseudosuchians became extinct at the end of the Triassic (Lucas & Tanner, 2015;Nesbitt et al., 2013) and, with them, the last occurrences of pseudosuchian endothermy. ...
Pseudosuchia, one of the two main clades of Archosauria, is today only represented by some 20 extant species, the crocodilians, representing only a fraction of its extinct diversity. Extant crocodilians are ectotherms but present morphological and anatomical features usually associated with endothermy. In 2004, it was proposed that pseudosuchians were ancestrally endothermic and the features observed in extant crocodilians are the remains of this lost legacy. This contribution has two parts: the first part covers 20 years of studies on this subject, first exploring the evidence for a loss of endothermy in extant crocodilians, before covering the variety of proxies used to infer the thermophymetabolic regime of extinct pseudosuchians. In the second part, the quantitative results of these previous studies are integrated into a comprehensive ancestral state reconstruction to discuss a potential scenario for the evolution of thermometabolism. Pseudosuchian endothermy would then have been lost close to the node Crocodylomorpha. The end‐Triassic mass extinction is proposed to have played the role of a filter, leading to the extinction of endothermic pseudosuchians and the survival of ectothermic ones. This difference in survival in Pseudosuchia is compared to those of dinosaurs, and difference in their metabolism is also considered. Pseudosuchian endothermy might have been of a different level than the dinosaurian one and more studies are expected to clarify this question.
... The same distinct palynofloral ETE occurs ~6 kyr before the earliest member of the North Mountain Basalt, whereas the initial CAMP extrusive pulse in Morocco coincides with the ETE ( 21 ). In the case of North Mountain Basalt pulses DG NM 1 and DG NM 2 in Nova Scotia (and correlatives DG T 2 and DG T 3 in Morocco), the palynofloral assemblage of the basal Scots Bay Member of the McCoy Brook Formation immediately above the NMB is very different than that of the Blomidon Formation immediately below the NMB, with only 2 of the 26 listed palynoflora species ( 24 ) in common and with a very low percentage of Classopollis . The palynofloral change has nonetheless been regarded as showing little difference in age between the post-ETE in the uppermost Blomidon Formation (see also ref. 23 ) and the McCoy Brook Formation with no mass extinction. ...
The end-Triassic extinction (ETE) on land was synchronous with the initial lavas of the Central Atlantic Magmatic Province (CAMP) and occurred just after the brief 26 thousand year (kyr) reverse geomagnetic polarity Chron E23r that can be used for global correlation. Lava-by-lava paleomagnetic secular variation data, previously reported from Morocco and northeastern United States combined with our data for the North Mountain Basalt from the Fundy Basin of Canada show that the initial phase of CAMP volcanism occurred in only five directional groups or pulses each occupying less than a century. The first four directional groups occur during a ~40 kyr period based on available astrochronology and U-Pb geochronology. The coincidence of the initial major pulse of CAMP volcanism with the ETE points to short-lived volcanic winters albedo-induced by sulfate aerosols as a plausible key agent of the extinctions in the tropical continental realm, whereas looser correlations allow prolonged CO 2 emissions to contribute to more long-ranging effects in the marine realm via ocean acidification and longer-term warming.
... The malformed specimens of Classopollis sp., when in tetrads, exhibit one of the four grains of the tetrad that appears much darker and smaller, sometimes with lack of ornamentation compared to the other pollen grains. These abnormalities in the aspect of the pollen grains of Classopollis sp. could be indicative of environmental stress related to atmospheric pollution, volcanic mercury (that could be related to the Eastern North America CAMP volcanism), and UVB radiation, generating mutagenesis in the land plants at the end of the Triassic (Visscher et al., 2004;Foster and Afonin, 2005;Whiteside et al., 2007Whiteside et al., , 2010Cirilli et al., 2009;Filipiak and Racki, 2010;Kürschner et al., 2013;Hochuli et al., 2017;Lindström et al., 2019;Vajda et al., 2023). The lack of typical age-indicative sporomorphs does not allow us to determine this section's age more precisely and better define stratigraphic constraints. ...
This paper presents the results of palynostratigraphic studies in the Silves Group in the Algarve Basin, Portugal. From bottom to top comprises the Silves Sandstones, the Silves Marl-Carbonate Evaporitic Complex, and the Volcano-Sedimentary Series. This study aims to detail the age of the Silves Group, bracketing the Triassic-Jurassic transition, using palynology. For this purpose, 250 samples were collected from 14 main sections. Previous results from a section above the Variscan unconformity, enabled to date the base of the Silves Sandstones and the onset of the Mesozoic sedimentary cycle in the Algarve Basin to lower Carnian. In this work, the top of the Silves Sandstones, containing Camerosporites secatus, Enzonalasporites vigens, Granuloperculatipollis rudis, Lagenella martinii, Patinasporites densus, Samaropollenites speciosus, and Vallasporites ignacii, is dated to the upper Carnian. The base of the Silves Marl-Carbonate Evaporitic Complex, consisting of Alisporites sp., Araucariacites australis, Classopollis meyerianus, Classopollis torosus, Paracirculina quadruplicis and Triadispora sp., indicates an upper Carnian age. The presence of Alisporites diaphanus, Araucariacites australis, Cerebropollenites macroverrucosus, Classopollis meyerianus, Classopollis torosus, Perinopollenites elatoides, Calamospora mesozoica, and Kraeuselisporites reissingeri allows to date the top of the Silves Marl-Carbonate Evaporitic Complex as upper Rhaetian-lower Hettangian. This study allows to date the Silves Group in the Algarve Basin from the lower Carnian to lower Hettangian (Triassic-Jurassic boundary) for the first time. The Carnian microflora provides new insights of the Onslow Microflora in the Western Tethys.
... There is no direct evidence of the CAMP in the LB, except for the southernmost part of the basin (Azerêdo et al., 2003;Kullberg et al., 2013). Nevertheless, the secondary effects of the volcanism, such as acid rain, the acidification of freshwater and global warming due to greenhouse effect, are factors that contributed to the climatic changes and may have had an impact on the flora of this age (Hesselbo et al., 2002;Guex et al., 2004;Marzoli et al., 2004;Tanner et al., 2004Tanner et al., , 2007Nomade et al., 2007;Schaltegger et al., 2008;Van de Schootbrugge et al., 2008Cirilli et al., 2009Cirilli et al., , 2015Cirilli et al., , 2018Deenen et al., 2010;Lindström, 2016;Davies et al., 2017;Lindström et al., 2019;Panfili et al., 2019;Capriolo et al., 2020). Furthermore, the increase in tectonic activity and changes in sea level at the TJB are also related to numerous sedimentary hiatuses in the Western European basins (Lindström et al., 2017a, b;Schneebeli-Hermann et al., 2018). ...
The Silves Group of the Lusitanian Basin in Portugal represents the initial infill of the continental rifting basins that formed during the breakup of northern Pangaea regions. Evaporites, especially halite, mark the transition from continental to marine settings and the beginning of the deposition in passive margin basins. This work presents the results of the palynostratigraphic and palynofacies analysis of two partial sections from the Pereiros Formation at the top of the Silves Group. The two sections are composed of sandstones, mudstones and dolostones interpreted as deposited in fluvial and lacustrine settings without apparent marine influence. The palynological content is diverse and wellpreserved, dating both sections to the early Hettangian (Lower Jurassic), indicated by the presence of spores Ischyosporites variegatus, Kraeuselisporites reissingeri, Porcellispora longdonensis and the pollen grains Perinopollenites elatoides and Pinuspollenites minimus. The palynological content of one of the sections (Lamas I) is noticeable by microforaminifera linings, suggesting evidence for a hitherto marine incursion at this age in the Silves Group stratigraphy. The beds that yielded the microforaminifera linings are interpreted as having been deposited in an estuarine-type setting, created by the first and short-lived marine transgressive event in the Lusitanian Basin during the early Hettangian.
... It is regarded as one of the characteristic guide forms of the Rhaetian (e.g. Bonis et al. 2009;Cirilli et al. 2009;Hillebrandt et al. 2013), or at least a typical Rhaetian taxon (Lindström 2016). Its last occurrence (LO) has been widely accepted as the marker of the end-Triassic (Bonis et al. 2009(Bonis et al. , 2010bCirilli 2010;Hillebrandt et al. 2013;Sha et al. 2015;Lindström 2016 and references therein), though it ranges from the uppermost Norian to the top of the Rhaetian and even the most basal Hettangian (e.g. ...
The vast, widely-exposed terrestrial (lacustrine to fluvial) Upper Triassic-Jurassic (except Tithonian), successions of the Junggar Basin, not only record most of the stratigraphic boundaries of the Upper Triassic and Jurassic, including the Triassic-Jurassic boundary (TJB), Hettangian-Sinemurian, Sinemurian-Pliensbachian, Pliensbachian-Toarcian, Lower-Middle Jurassic, Middle-Upper Jurassic, Oxfordian-Kimmeridgian boundaries, but also record a range of the geologic, organic, palaeogeographic, palaeoclimatic events, known to have happened globally in the Late Triassic and Jurassic. The TJB is placed in the stratigraphic interval of the First Occurrence (FO) of Retitriletes austroclavatidites and Callialasporites dampieri and the Last Occurrence (LO) of Lunatisporites rhaeticus . The end-Triassic mass extinction (ETE) is characterized by the disappearance of most of the sporomorph and macro-plant taxa. The ETE occurred before the FO of the sporomorph Cerebropollenites thiergartii , and ended after it when life began to revive. The Junggar Basin was situated at a high latitude during the Late Triassic-Early Jurassic Pliensbachian ‘hothouse’ and ‘greenhouse’ periods. The Late Triassic-Middle Jurassic Bajocian was humid and warm, and rich in coal swamps, except the Toarcian, which yields little coal because it was relatively warmer and drier. It became arid from the early Late Jurassic Oxfordian.
... Although the North Mountain Basalt age had long been assigned to the start of the Jurassic Period (Olsen 1997), new work by Cirilli et al. (2009) showed that latest Triassic microfossils are present in a few meters of sediment above the basalt. The basalt and its stratigraphic features are prominent in new assignments of the Triassic-Jurassic boundary age and its mass extinction event (Deenen et al. 2010), assisted by a series of precise radioisotopic analyses (Fig. 3). ...
... Pangaea's break-up was accompanied by intense volcanism that occurred before, during, and after rifting of the Central Atlantic Ocean since the late Triassic (Beutel et al., 2005;Marzoli et al., 2018). This magmatism occurred at approximately 200 to 202 Ma and produced the Central Atlantic Magmatic Province (CAMP), which represents one of the most significant large igneous provinces (LIPs) worldwide; the magmatic activity could have triggered geological processes that contributed to the end-Triassic mass extinction (Marzoli et al., 1999;Vérati et al., 2007;Nomade et al., 2007;Vérati et al., 2007;Cohen and Coe, 2007;Cirilli et al., 2009;Blackburn et al., 2013;Panfili et al., Panthalassic Ocean South America . Three million km 3 of dominantly tholeiitic magma forming sills, dykes, pyroclastic successions, and surface flows were erupted along the margins and inland regions of continents covering 11 million km 2 in SW Europe, NW Africa, southeastern North America, and NE South America (Hodych and Hayatsu, 1980;Papezik and Hodych, 1980;Deckart et al., 2005;Nomade et al., 2007;Kontak, 2008;Bensalah et al., 2011;Torsvik and Cocks, 2013;Bertrand et al., 2014;Shellnutt et al., 2017;Marzoli et al., 2018;Denyszyn et al., 2018;Heimdal et al., 2018;Svensen et al., 2018;Oliveira et al., 2018;Rezende et al., 2021). ...
The opening of the Central Atlantic Ocean was accompanied by ascending plume zones that generated large igneous provinces (LIPs), such as the Central Atlantic Magmatic Province (CAMP), with voluminous lava flows and outpourings. One of the best records of the CAMP in the West Gondwana is the Jurassic volcanic-sedimentary succession exposed in the western Parnaíba Basin, northern Brazil. Diagenetic and hydrothermal processes are discussed, focusing on the lava-sediment interaction. The siliciclastic sediments called “intertrap deposits” record a wet desert system characterized by fluvial-aeolian and shallow lake deposits engulfed by lavas of the CAMP at approximately 200–202 Ma. The facies and petrographic studies, based on a drill core and outcrops, led to the interpretation of the palaeoenvironmental and diagenetic evolution of the intertrap deposits. The intertrap deposits are sandwiched by basalts and may be organized in seven sedimentary facies, grouped into two facies associations: 1) ephemeral braided river deposits (FA1), which consist of medium- to coarse-grained pebbly sandstone with poorly sorted angular to sub-rounded grains (basaltic fragments and quartz) and low-angle cross-bedding, even-parallel stratification, and trough cross-stratification, and 2) pond/shallow lake deposits (FA2) composed of tabular beds of sandstone/siltstone rhythmite and laminated mudstone. The main architectural elements of intertrap deposits are 1) channels on volcanic substrate, 2) sand sheets deposited over pre-existent lava topography, 3) tabular beds with laminated rhythmites, and 4) sand-filled fissures/fractures and clastic dykes. The intensification of magmatic processes due to the disruption of Pangaea promoted the formation of extensive volcanic plains, whereas wet desert settings were developed during the quiescent intervals between lava flow episodes. Fluvial channels with subaqueous dunes and sand sheets were incised into the basaltic substrate. The abandoned fluvial plains were affected by flash floods that promoted mechanical infiltration of clays, forming coatings over grains. The heat flow and hydrothermal activity of volcanic rocks increased the devitrification of glassy clasts, releasing silica and precipitating low-temperature authigenic mineral assemblages. The most common pore-filling process was the massive precipitation of early diagenetic-hydrothermal minerals, including chalcedony, poikilotopic zeolite, megaquartz, and haematite, which partially obliterated the primary porosity and permeability. These exceptional conditions of cementation triggered by basalt eruptions precluded the modification of a primary framework by late stages (post-Jurassic) burial diagenesis. The intertrap sandstones represent the last lava-sediment interaction related to the CAMP recorded in West Gondwana.
... For example, the strata slightly below flood basalts in the Newark rift basins in the eastern North America display a relatively sharp transition from diverse assemblages of monsaccate and bisaccate pollen to an overlying assemblage containing 60%À90% Corollina meyeriana spores, and this level was considered as a regional marker for the Triassic/ Jurassic boundary (e.g., Cornet, 1977;Cornet and Olsen, 1985;Olsen, 1993, 1995). However, similar palynological changes are recorded near the base of the typical Rhaetian of Europe (e.g., Schuurman, 1979;Orbell, 1983;Van Veen, 1995), therefore some palynologists have interpreted this level to be a major hiatus that includes most of the Rhaetian stage (e.g., Cirilli et al., 2009), as was initially also suggested by the conchostracan assemblages Weems, 2005, 2010). This interpretation of the absence of the uppermost Norian and most of the Rhaetian between the radioisotopic-dated flood basalts and the underlying cyclescaled magnetozones of the Newark Supergroup lacustrine strata contributed to a pair of Late Triassic age models in GTS2012 (Ogg, 2012); but it now seems from later magnetostratigraphic correlations to marine deposits and to levels dated by radioisotopes in a reference borehole on the Colorado Plateau that there is no significant hiatus in the uppermost Rhaetian of the Newark Basin (Kent et al., 2017(Kent et al., , 2018. ...
The Triassic is bound by two mass extinctions that coincide with vast outpourings of volcanic flood basalts. The Mesozoic begins with a gradual recovery of plant and animal life after the end-Permian mass extinction. Conodonts and ammonoids are the main correlation tools for marine deposits. The Pangea supercontinent has no known glacial episodes during the Triassic, but the modulation of its monsoonal climate by Milankovitch cycles left sedimentary signatures useful for high-resolution scaling. Dinosaurs begin to dominate the terrestrial ecosystems in latest Triassic. In contrast to the rapid evolution and pronounced environmental changes that characterize the Early Triassic through Carnian, the Norian–Rhaetian of the Late Triassic was an unusually long interval of stability in Earth history.
... The plant extinction is recorded in Greenland (McElwain et al. 1999 and is associated with a second negative δ 13 C recorded in the Hettangian Psiloceras planorbis beds (coeval with P.pacificum). In the Newark basin this second extinction, mainly continental, occurs higher than the youngest Triassic-looking sporomorphs embedding Lower Jurassic CAMP basalts: These floras are still of Triassic affinity (Cirilli et al. 2009) and are coeval with the flora of "Rhaetian" affinity recorded in the Tiefengraben Member of the Lower Jurassic in the TJB stratotype at Kuhjoch (Austria, Bonis et al. 2009): all the sporomorphs present in the Lower Jurassic of that section already exist in the Triassic. In other words they are not serious markers for the base of the Jurassic. ...
... Analyses of micro-and macrofloral abundance and diversity indicate severe changes in land plant cover during the latest Rhaetian in NW Europe (van de Schootbrugge et al., 2009;van de Schootbrugge and Wignall, 2016), Greenland (McElwain et al., 1999), and North America (Cirilli et al., 2009;Fowell et al., 1994). Detailed palynological studies of cores and outcrops in Denmark , Sweden (Lindström and Erlström, 2006), Germany (Heunisch et al., 2010), England (Bonis et al., 2010), Hungary , and Austria (Bonis et al., 2009) show simultaneous changes in floral assemblages over a very broad area. ...
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.
... Wilson's classic model drew directly on the Central Atlantic basin and its history of repeated closures and reopenings as a primary example of global tectonic processes. End-Triassic rifting was associated with the emplacement of one of the most voluminous continental flood basalt provinces in Earth history (Figure 1), the Central Atlantic Magmatic Province (CAMP; Marzoli et al., 1999), an event significant enough to have likely triggered the end-Triassic mass extinction (Capriolo et al., 2020;Cirilli et al., 2009;Davies et al., 2017;Heimdal et al., 2018;Hesselbo et al., 2002;Marzoli et al., 2004). Major continental rifting events in geologic history are commonly associated with the eruption of a large igneous province (LIP), but the causal relationships linking rifts with LIPs remain unclear. ...
The driving processes responsible for producing the Central Atlantic Magmatic Province, the Large Igneous Province associated with end‐Triassic rifting of Pangea, remain largely debated. Because their compositions encompass most of the Central Atlantic basalt spectrum, tholeiites from southern Eastern North America are considered pivotal for identifying magma origins. New ¹⁷⁶Hf/¹⁷⁷Hf measurements for 201 Ma Eastern North American tholeiites dominantly record a local petrogenetic history. Their εHf ratios, corrected to an emplacement age of 201 Ma (−7.85 to +5.86), form a positive but shallowly sloped array slightly deviating from the terrestrial array on a εHf versus εNd diagram. Comparison of ¹⁷⁶Hf/¹⁷⁷Hf to other isotope ratios and trace elements helps to rule out several petrogenetic scenarios, particularly mixing of melts from global depleted or enriched mantle components. In contrast, partial melting of subduction‐metasomatized mantle can explain the parental magma composition for southern Eastern North America. Such metasomatism likely occurred during Paleozoic subduction around Pangea and may have been dominated by sediment‐derived fluid reactions. The observed ¹⁷⁶Hf/¹⁷⁷Hf versus ¹⁴³Nd/¹⁴⁴Nd array may reflect subsequent assimilation of lower continental crust, perhaps together with limited direct melting of recycled continental crust in the asthenosphere. The proposed recycling scenario does not specifically support or preclude a mantle plume origin for the Central Atlantic Magmatic Province but instead points toward the presence of a distinct local mantle source and crustal assimilation processes during magma transport. Detailed understanding of these local effects is needed in order to more accurately understand the origins of Large Igneous Provinces.
... High-precision dates suggest about 570,000 years between the earliest and latest basin basalts , based on basin stratigraphy correlated with Milankovitch climatic cycles. The Triassic-Jurassic boundary occurs above the oldest ITi basalts in eastern North America (Cirilli et al., 2009), but the end-Triassic extinction horizon is still defined a meter or so beneath the oldest basin basalt . Older basalts and large sills (Davies et al., 2017) exist in Morocco (Deenen et al., 2010) that precede the end-Triassic mass extinction for which it is now generally recognised that the CAMP is the prime causal candidate (Blackburn et al., 2013). ...
The breakup of Pangaea was accompanied by extensive, episodic, magmatic activity. Several Large Igneous Provinces (LIPs) formed, such as the Central Atlantic Magmatic Province (CAMP) and the North Atlantic Igneous Province (NAIP). Here, we review the chronology of Pangaea breakup and related large-scale magmatism. We review the Triassic formation of the Central Atlantic Ocean, the breakup between East and West Gondwana in the Middle Jurassic, the Early Cretaceous opening of the South Atlantic, the Cretaceous separation of India from Antarctica, and finally the formation of the North Atlantic in the Mesozoic-Cenozoic. We demonstrate that throughout the dispersal of Pangaea, major volcanism typically occurs distal from the locus of rift initiation and initial oceanic crust accretion. There is no location where extension propagates away from a newly formed LIP. Instead, LIPs are coincident with major lithosphere-scale shear movements, aborted rifts and splinters of continental crust rifted far out into the oceanic domain. These observations suggest that a fundamental reappraisal of the causes and consequences of breakup-related LIPs is in order.
... The presence of Cheirolepidiaceae pollens (e.g., Classopollis sp.) and fern-producing spores (e.g., Deltoidospora mesozoica, Dictyophyllidites mortonii, D. harrisi, Trachysporites fuscus) indicates a general warm-humid climate, as already postulated in previous papers (i.e., Pieńkowski et al., 2012 for references). Evidences of a global increase in humidity starting from Late Triassic are largely documented by several authors and have been related to the degassing of basaltic flows from the Central Atlantic Magmatic Province (Cirilli et al., 2009Van de Schootbrugge et al., 2009;Bonis et al., 2010;Schoene et al., 2010;Ruhl and Kürschner, 2011;Schaller et al., 2011;Lindströ;Davies et al., 2017). ...
Thermal maturity of six organic rich samples from Jurassic continental successions cropping out in the Holy Cross Mountains in Central Poland, has been characterized by classic thermal maturity indicators, micro-Raman spectroscopy and Palynomorph Darkness Index, in order to create a multi-method workflow for complex palynofacies thermal maturity assessment. Transmitted light observations on dispersed organic matter define a Hettangian lacustrine depositional environment, characterized by periods of reducing/oxidizing conditions and variable sedimentation rates. Thermal maturity detected by classical maturity indicators and PDI indicates an early maturation stage of hydrocarbon generation and is in agreement with spectroscopic analyses performed on phytoclast groups. Moreover, Raman parameters in the sporomorph group indicate a systematic shift toward a lower degree of aromatization compared to the phytoclast group. Finally, the multivariate statistical analysis performed on Raman spectra is found to be a promising tool to define and predict the heterogeneity of dispersed organic matter in sediments.
... É sugerido por alguns autores um aquecimento global devido a este efeito de estufa, associado ao CAMP, estimado em 3º a 4 ºC, resultado de um aumento significativo de CO2 e SO2 (Marzoli et al., 1999(Marzoli et al., , 2004McElwain et al., 1999;Hesselbo et al., 2002;Guex et al., 2004;Tanner et al., 2004Tanner et al., , 2007Schaltegger et al., 2008;Van de Schootbrugge et al., 2008, embora esteja ainda por resolver se as erupções decorreram antes (Marzoli et al., 2004(Marzoli et al., , 2008 ou depois da transição Triásico -Jurássico . Estudos palinológicos mais recentes (Marzoli et al., 2004;Cirilli et al., 2009) ...
This work presents the palynostratigraphic study of the Silves Group, exposed between the Coimbra-Penela sector, in the Lusitanian Basin, West of Portugal, and dating from the Upper Triassic - Lower Jurassic. This unit includes, from the base to the top, the formations of Conraria, Penela, Castelo de Viegas and Pereiros, most of them analyzed in the present work. No longer belonging to the Silves Group, was also analyzed the basis of the Coimbra Formation.
From the analysis of 9 partial outcrops of the Silves Group in this region, 39 samples were collected for palynological analysis, aiming at a biostratigraphic (and, consequently, chronostratigraphic) deepening. Throughout this study 51 palynomorphs were identified: 23 spore taxa and 28 pollen taxa. Four palynological associations were defined, which were compared with associations described in other European sectors. With the data obtained during this study, an informal palinozonation is proposed, for the first time.
The Conraria Formation dates from the upper Carnian (upper Tuvalian) to Norian age where the Granuloperculatipollis rudis zone (Gr zone) is defined. Complete the association the pollens Paracirculina quadruplicis, Classopollis meyeriana, among others, occurring in a rare and common way throughout the association. Due to lithologic and faciological limitations, the Penela and Castelo Viegas formations did not allow a palinostratigraphic zonation. In the Pereiros Formation, two informal zones were described, namely Ischyosporites variegatus - Kraeuselisporites reissingeri (VR zone) and Pinuspollenites minimus (Pm zone) of Hettangian age. The basal part of the VR zone is not described due to lack of information. It is worth noting the clear dominance of Classopollis meyeriana pollen throughout the association. This taxa also dominates the Pm zone together with the pollen Classopollis torosus and Araucariacites sp.. The faciological limitations of the top of the Castelo Viegas Formation, regarding its absence in palynomorphs, do not allow a discussion about the Triassic - Jurassic boundary. For the Coimbra Formation, no zonation was proposed, considering that the presented material was similar to the Pm zone, suggesting that the age of the base of the Coimbra Formation should date from the upper part of Hettangian.
The biostratigraphic review established in this work allows us to detail the age of the litostratigraphic succession of the Silves Group in the northern portion of the Lusitanian Basin, providing new evidence of ecosystems and climatic changes during the Triassic-Jurassic transition.
... The Late Triassic age is further confirmed by the absence of Jurassic palynological diagnostic markers such as Cerebropollenites thiergartii and/or the acme of Polypodiisporites polymicroforatus (Hillebrandt et al., 2013;Lindström et al., 2017). The Moroccan palynological associations dominated by the Classopollis group in association with P. densus, coming from the sedimentary layers intercalated with the Intermediate and Upper Basalt, are very similar to those recorded in the continental sedimentary successions of Fundy, Nova Scotia (Fowell and Traverse, 1995;Cirilli et al., 2009) and Newark basins, eastern North America (Whiteside et al., 2010 and references cited therein). Both in the Fundy basin and in the Newark basin, the highest record of P. densus occurs below the oldest CAMP lava flow, whilst, in Morocco, it does not disappear before the first CAMP basalt. ...
Different lines of evidence suggest that the main trigger mechanism for the end-Triassic mass extinction was the release of volcanic and thermogenic gases during the emplacement of the Central Atlantic Magmatic Province (CAMP). However, the short duration of the biotic and environmental crisis and the magmatic activity hinders precise control on the relative timing between these events, especially when comparing the continental sedimentary
record where there is no independent age control with the magmatic record. In order to disentangle the temporal relationships of the end-Triassic events, we have analyzed the palynology of the sedimentary strata interlayered with CAMP lava flows from eleven sites throughout Morocco (Western and Central High Atlas, Middle Atlas, Western Meseta). The recovered sporomorphs help to constrain the age of CAMP volcanism, allowing the stratigraphic correlation of the basaltic volcanism with the extinction and geochemical records such as carbon-isotope and mercury shifts, recorded in marine sedimentary successions worldwide. Our new data show that CAMP erupted almost entirely during the end-Triassic mass extinction interval, just before the Triassic–Jurassic boundary (Tr-J). Hence, a very rapid emplacement of the CAMP very likely triggered the carbon cycle and ecological disruption at the Tr-J boundary.
... This has been interpreted as a consequence of intense monsoonal activity (Parrish, 1993;Satterley, 1996;Sellwood and Valdes, 2007;Bonis and Kürschner, 2012). In addition, the onset of igneous and volcanic activity within the Central Atlantic Magmatic Province (CAMP), is generally believed to have strongly influenced the climate change due to the release of volcanic gases (mainly CO 2 and SO 2 ) into the ocean-atmosphere system (Marzoli et al., 2004;Cirilli et al., 2009;van de Schootbrugge et al., 2009;Lucas et al., 2011;Ruhl et al., 2011;Schaller et al., 2011;Pálfy and Zajzon, 2012;Vajda et al., 2013;Bond and Wignall, 2014;Lindström, 2016;Davies et al., 2017;Lindström et al., 2017b). Consequently, the end-Triassic mass extinction (ETE) has been attributed to the huge amount of greenhouse-gas emissions in the atmosphere and in the ocean water, and associated with the ≈3-6% negative carbon isotope excursion, recorded in both terrestrial and marine environments (Schoene et al., 2010;Whiteside et al., 2010;Ruhl et al., 2011;Dal Corso et al., 2014;Lindström, 2016;Lindström et al., 2017b). ...
A combined palynofacies and lithofacies analysis was carried out on two borehole successions (Streppenosa 1 and Bimmisca 1) from the Hyblean Plateau Petroleum System (SE Sicily, Italy). It was found that both the wells penetrated the most important source and seal rocks of the Sicilian region (Noto and Streppenosa formations), previously assigned to the Late Triassic-Early Jurassic, deposited within a carbonate platform-basin system. Based on new palynological data, the organic rich succession (Noto Formation and Upper Streppenosa Member) can now be entirely assigned to the Rhaetian, thus constraining its deposition to a time interval characterized by increasing global humidity and seasonality. The integrated palynofacies and lithofacies data enabled characterization of the timing of the drowning phases of the carbonate platform-basin system as being controlled by relative sea level changes mostly triggered by the Triassic extensional tectonic activity. During the first phase of the relative sea-level rise, clayey and organic-rich sediments were deposited only in the deepest portion of the basin. As the sea level continued to rise, the entire system drowned completely and suboxic-anoxic basinal sediments were deposited across the whole Hyblean region, onlapping the shallow-water facies. In the meantime increasing global humidity contributed to an increased freshwater input in the marine depositional system as documented by the presence of fern spores and clay. It caused water stratification and subsequent anoxia at marine basins, favoring the preservation of sedimentary organic matter. This atmospheric change could be related to the degassing of the Central Atlantic Magmatic Province.
... For example, the spore M. Zaffani et al. Earth-Science Reviews 178 (2018) 92-104 and pollen end-Triassic extinction pattern in the Newark Basin (Fowell and Olsen, 1993) appears to contradict other palynologic and paleontological works (Weems and Olsen, 1997;Cirilli et al., 2009). One observation from the study herein is that the transition from the Zu3c submember (uppermost Zu Limestone Fm) to the Malanotte Formation is similar to that in the Austrian sections; the meter-thick marly silty horizon marking the base of the Malanotte Formation appears comparable to the base of the Schattwald Beds, the marly unit at the base of the Tiefengraben Member (McRoberts et al., 1997;Galli et al., 2005). ...
The green alga Palaeodasycladus was recognized in Lower Jurassic shallow-marine high-energy calcarenites of the Choč Nappe (Hronicum Domain) in the Tatra Mts in Poland. This occurrence indicates the most Northern record of Palaeodasycladus as it is known mostly from the southern part of the Western Tethys. The stratigraphic range of Palaeodasycladus (Norian, Sinemurian–Pliensbachian) and the upper Pliensbachian age of the overlying calcarenites (previous data on the basis of brachiopods) suggest that the studied part of the section was deposited during the Sinemurian–early Pliensbachian. The previous and current reports on occurrences of Palaeodasycladus allowed determination of a new northern palaeogeographic range of the shallow-marine Mediterranean biota during the Early Jurassic time.
... Moreover, the use of pollen and spores for the definition of the ETE is the subject of much debate. For example, the spore and pollen end-Triassic extinction pattern in the Newark Basin (Fowell and Olsen, 1993) appears to contradict other palynologic and paleontological works (Weems and Olsen, 1997;Cirilli et al., 2009). ...
The links between large-scale volcanism, carbon cycle perturbations and the biotic crises at the End-Triassic Extinction event (ETE) are not well understood. The ETE seems to be marked by three carbon isotope excursions (CIEs) likely triggered by different eruptive phases of the Central Atlantic Magmatic Province (CAMP). These three CIEs appear to occur during the late Rhaetian, close to the Triassic/Jurassic boundary (TJB), but the relative timing connecting the volcanism, carbon perturbations and extinctions is still subject to debate resulting from: i) the difficulties in long-distance biostratigraphic correlations of Rhaetian successions due to the step-like extinction pattern characterizing the ETE, and to the lack of globally correlatable key-fossil group(s) across the system boundary; ii) the limit of coverage of available δ¹³C profiles to the system boundary interval, rather than the entire Rhaetian; iii) the inherent difficulties in correlating CIEs without clear biostratigraphic markers. Here we present a δ¹³Corg curve from the Lombardy Basin which covers for the first time the entire Rhaetian. Using this chemostratigraphy, we propose two possible correlations (option 1 and option 2) with other late Rhaetian to early Hettangian successions worldwide. These two possible correlations rely on a combination of paleontological (ammonoids, pollens, conodonts), lithostratigraphic and geochemical constraints. Option 2 in particular has important implications for the causality and geochronology of the ETE events by suggesting that the sharp negative peak usually considered to be the “initial” CIE in the Lombardy might represent a carbon perturbation within the negative trend of the “main” CIE. This implies that a reconsideration of the succession of biotic events occurring during this time interval is required.
... The volcanics (flows and intrusions) of the Central Atlantic Magmatic Province (CAMP), were emplaced at the end of Triassic and beginning of the Early Jurassic (e.g., Olsen 1997;Withjack et al. 1998;Marzoli et al. 1999Marzoli et al. , 2004Marzoli et al. , 2011Knight et al. 2004;Golonka 2007a;Cirilli et al. 2009). CAMP constitutes one of the largest known Phanerozoic flood basalt provinces. ...
The Late Triassic was the time of the Early Cimmerian and Indosinian orogenies that closed the Paleotethys Ocean, which occurred earlier in the Alpine-Carpathian-Mediterranean area, later in the Eastern Europe-Central Asia and latest in the South-East Asia. The Indochina Southeastern Asian and Qiangtang plates were sutured to South China. The new, large Chinese-SE Asian plate, including North and South China, Mongolia and eastern Cimmerian plates, was consolidated by the end Triassic, leaving open a large embayment of Panthalassa, known as Mongol-Okhotsk Ocean, between Mongolia and Laurasia,. The Uralian Orogeny, which sutured Siberia and Europe continued during Late Triassic times and was recorded in Novaya Zemlya. The onset of Pangaea break-up constitutes the main Late Triassic extensional event. Continental rifts originating then were filled with clastic deposits comprising mainly red beds. The pulling force of the north-dipping subduction along the northern margin of Neotethys caused drifting of a new set of plates from the passive Gondwana margin, dividing the Neotethys Ocean. Carbonate sedimentation dominated platforms on the Neotethys and Paleotethys margins as well as the Cimmerian microplates. Synorogenic turbidites and postorogenic molasses were associated with the Indosinian orogeny. The late stages of the Uralian orogeny in Timan-Pechora, Novaya Zemlya and eastern Barents regions filled the foreland basin with fine-grained, molasse sediments. Siliciclastics were common in the Siberia and Arctic regions. The widespread, large magnitude, base-level changes of the Late Triassic are interpreted as an expression of relatively rapid and substantial changes in the horizontal and vertical stress fields that affected the Pangaea supercontinent. Such stress changes may be due to abrupt changes in the speed and/or direction of plate movements, which episodically affected Pangaea.
... In most of these palynological studies, the non-palynomorph component (mostly the structured/amorphous organic matters (SOM/AOM) or resins) is not discussed or vice versa, the paper focuses on non-palynomorphs but not on the palynomorphs. Very few studies have used quantitative methods on the entire palynofacies (e.g., Cirilli et al., 2009). ...
Palynomorphs and other organic particles are basic key components of palynofacies, yet quantitative analyses of all types are rarely used together to investigate organic matter assemblage changes and evaluate the driving forces behind the observed changes. In this paper, eight organic-walled microfossil and particle morphologies (sporopollen, Pediastrum, Concentricystes, fungi, dinoflagellate cysts, structured/amorphous organic matters, stomatal apparatus and scolecodonts) are tabulated and their concentrations and fluxes are evaluated over the past 17 million years (Ma) in sediments recovered from the South China Sea at International Ocean Discovery Program (IODP) Site U1433. Overall, these morphologies show roughly similar increasing trends but with different levels of fluctuations. The uniform increase in all morphologies at ∼. 8. Ma (named the ∼. 8. Ma event) is the most notable feature of the past 17. Ma. To explain the trend, and because these various organic matters reflect various environmental conditions, we argue that the uniformity of the signal implies that tectonically-driven basin and drainage evolution played the key role, rather than paleoclimate (Asian summer monsoon). The ∼. 8. Ma event was likely triggered by the onset of the Mekong River in its present location, although the role of monsoon evolution cannot be excluded completely.
... The presence of Classopolis sp in the palynological assemblage (Van der Hammen and Burger, 1966) of the Manari Formation that overlies the basalts; is identical to that occurring in other CAMP sites (e.g. Marzoli et al., 2004;Cirilli et al., 2009), reinforcing that they are part of the CAMP magmatism. The Ar-Ar dating of Apoteri magmatism (Nomade et al., 2007) is a further support this evidence. ...
In northern Brazil, Roraima state and southwestern Guyana, basalt flows characterized by inflated pahoehoe structure occur along the margins of the Tacutu Rift Valley, dykes intrude the Paleoproterozoic basement close to the boundary of the rift system with concordant, NE-trend. The dykes and flows belong to Apoteri magmatism. New field, geochemical data (major, trace and rare-earth elements) and chemical stratigraphy of the Apoteri magmatism indicate petrographic and chemical homogeneity characteristic of continental tholeiitic basalts. The basalt flows of Morro Redondo and Nova Olinda sites show two distinct chemical groups: a) the lower flows with intermediate TiO2 content (ITi group) ranging from 1.09 to 1.41 wt%, MgO (5.64–6.46 wt%) and Ni (43–53 ppm) contents; and b) the upper flows with lower TiO2 content (LTi group) = 0.75 to 0.78 wt%, higher MgO = 7.95–8.85 wt% and Ni = 105–115 ppm. The two magma types share many characteristics in high field strength elements (HFSE) and rare earth elements (REE), but in detail significant differences exist in REE ratios, e.g. (La/Yb)N of ∼4.0 for ITi and 3.2 for LTi and this may be explained by fractional crystallization. The chemical compositions of the Apoteri dykes are similar the ITi group analyses, suggesting that they have the same origin. The La/Ba versus La/Nb diagram is indicative of large ion lithophile elements (LILE) enrichment and LILE/HFSE fractionation in the mantle source, and the data favor a dominant subcontinental lithospheric mantle (SCLM) component in the origin of the Apoteri flows and dykes. These data show consistent similar chemical characteristics and correspond to other tholeiitic flows from the large Central Atlantic Magmatic Province (CAMP), especially eastern USA.
... The Mesozoic strata lie unconformably on Carboniferous and older rocks. The basalts which were emplaced just above the Triassic-Jurassic boundary are unconformably overlain by lacustrine limestones and continental clastic sedimentary rocks (Olsen et al. 1987;Cirilli et al. 2009). The Mesozoic rocks of the Bay of Fundy form a large, asymmetrical, plunging syncline that dips more-steeply on the northern side. ...
One of the defining characteristics of the basaltic rocks from the Early Jurassic Eastern North America (ENA) sub-province of the Central Atlantic Magmatic Province (CAMP) is the systematic compositional variation from South to North. Moreover, the tectono-thermal regime of the CAMP is debated as it demonstrates geological and structural characteristics (size, radial dyke pattern) that are commonly associated with mantle plume-derived mafic continental large igneous provinces but is considered to be unrelated to a plume. Mantle potential temperature (TP) estimates of the northern-most CAMP flood basalts (North Mountain basalt, Fundy Basin) indicate that they were likely produced under a thermal regime (TP ≈ 1450 °C) that is closer to ambient mantle (TP ≈ 1400 °C) conditions and are indistinguishable from other regions of the ENA sub-province (TPsouth = 1320–1490 °C, TPnorth = 1390–1480 °C). The regional mantle potential temperatures are consistent along the 3000-km-long ENA sub-province suggesting that the CAMP was unlikely to be generated by a mantle plume. Furthermore, the mantle potential temperature calculation using the rocks from the Northern Appalachians favors an Fe-rich mantle (FeOt = 8.6 wt %) source, whereas the rocks from the South Appalachians favor a less Fe-rich (FeOt = 8.3 wt %) source. The results indicate that the spatial-compositional variation of the ENA basaltic rocks is likely related to differing amounts of melting of mantle sources that reflect the uniqueness of their regional accreted terranes (Carolinia and West Avalonia) and their post-accretion, pre-rift structural histories.
... However, despite the age overlap between the marine and terrestrial records, the biostratigraphic definition of the ETE in continental basins is strongly debated. In particular, the definition of the ETE in the Newark basins is based on a pollen and spore turnover 24 that is questioned by other palynologic and paleontological studies 25,26 . Further confusing the continental record, are suggestions that there may be a hiatus in sedimentation under the Orange Mountain basalt in the Newark basin (e.g. ...
The end-Triassic extinction is one of the Phanerozoic’s largest mass extinctions. This
extinction is typically attributed to climate change associated with degassing of basalt flows
from the central Atlantic magmatic province (CAMP). However, recent work suggests that
the earliest known CAMP basalts occur above the extinction horizon and that climatic
and biotic changes began before the earliest known CAMP eruptions. Here we present new
high-precision U-Pb ages from CAMP mafic intrusive units, showing that magmatic activity
was occurring B100 Kyr ago before the earliest known eruptions. We correlate the early
magmatic activity with the onset of changes to the climatic and biotic records. We also report
ages from sills in an organic rich sedimentary basin in Brazil that intrude synchronously with
the extinction suggesting that degassing of these organics contributed to the climate change
which drove the extinction. Our results indicate that the intrusive record from large igneous
provinces may be more important for linking to mass extinctions than the eruptive record.
... There is now ample evidence that the giant Central Atlantic Magmatic Province (CAMP) largely erupted in the latest Triassic over a geologically short interval of time (Marzoli et al. 1999(Marzoli et al. , 2004Cirilli et al. 2009). A causal link to the end-Triassic mass extinction has long been proposed but there is still dispute over the proximate trigger of the extinctions. ...
The hypothesis that ocean acidification was a proximate trigger of the marine end-Triassic mass extinction rests on the assumption that taxa that strongly invest in the secretion of calcium-carbonate skeletons were significantly more affected by the crisis than other taxa. An argument against this hypothesis is the great extinction toll of radiolarians that has been reported from work on local sections. Radiolarians have siliceous tests and thus should be less affected by ocean acidification. We compiled taxonomically vetted occurrences of late Permian and Mesozoic radiolarians and analyzed extinction dynamics of radiolarian genera. Although extinction rates were high at the end of the Triassic, there is no evidence for a mass extinction in radiolarians but rather significantly higher background extinction in the Triassic than in the Jurassic. Although the causes for this decline in background extinction levels remain unclear, the lack of a major evolutionary response to the end-Triassic event, gives support for the hypothesis that ocean acidification was involved in the dramatic extinctions of many calcifying taxa.
doi:10.1002/mmng.201000017
... Previous works on CAMP lavas from Morocco suggested that CAMP volcanism preceded the Tr-J boundary and thus could be responsible for the associated biotic crisis . Such hypothesis is based on the presence of short geomagnetic reversals recorded in the intermediate unit of the Moroccan CAMP lava and correlated to the E23r anomaly of the Newark basin, USA ) and on palynological data suggesting an end-Triassic onset of CAMP volcanism in Morocco and Canada (Cirilli et al., 2009;Marzoli et al., 2004). However, the primary origin of these reversals has been recently challenged and proved to be the product of remagnetization and hydrothermal processes (Font et al., 2011). ...
The Central Atlantic Magmatic Province (CAMP) is one of the largest igneous provinces of the Phanerozoic and its formation is believed to be coeval with the biological crisis of the Triassic-Jurassic boundary (~201Ma). Other coeval lavas have been extensively studied in the United States and Morocco, however relatively little attention has been given to the CAMP lavas from the south of Portugal for which geochemical data have been recently published. Here we provide new rock magnetic and magnetostratigraphic data on the CAMP lavas cropping out in the Algarve basin, Southern Portugal, in order to better constrain their age and eruptions rates. Despite severe superficial alteration that characterizes the area, the selected rocks preserved their primary magnetic mineralogy, represented by an assemblage of fine grained Ti-poor titanomagnetite and accessorily hematite. After cleaning by alternating field, all samples show normal (positive) characteristic remanent magnetization confirming the absence of any negative polarity that might correspond to the well-known E23r subchron. VGP’s directions vary slightly within the lava pile (>5 m) suggesting quite rapid eruptions and a single magmatic pulse.
... Marzoli et al., 2004;Cirilli et al., 2009; ...
The temporal link between large igneous province (LIP) eruptions and at least half of the major extinctions of the Phanerozoic implies that large scale volcanism is the main driver of mass extinction. Here we review almost twenty biotic crises between the early Cambrian and end Cretaceous and explore potential causal mechanisms. Most extinctions are associated with global warming and proximal killers such as marine anoxia (including the Early/Middle Cambrian, the Late Ordovician, the intra-Silurian, intra-Devonian, end-Permian, and Early Jurassic crises). Many, but not all of these are accompanied by large negative carbon isotope excursions, supporting a volcanogenic origin. Most post-Silurian biocrises affected both terrestrial and marine biospheres, suggesting that atmospheric processes were crucial in driving global extinctions. Volcanogenic-atmospheric kill mechanisms include ocean acidification, toxic metal poisoning, acid rain, and ozone damage and consequent increased UV-B radiation, volcanic darkness, cooling and photosynthetic shutdown, each of which has been implicated in numerous events. Intriguingly, some of the most voluminous LIPs such as the oceanic plateaus of the Cretaceous were emplaced with minimal faunal losses and so volume of magma is not the only factor governing LIP lethality. The missing link might be continental configuration because the best examples of the LIP/extinction relationship occurred during the time of Pangaea. Many of the proximal kill mechanisms in LIP/extinction scenarios are also potential effects of bolide impact, including cooling, warming, acidification and ozone destruction. However, the absence of convincing temporal links between impacts and extinctions other than the Chicxulub-Cretaceous example, suggests that impacts are not the main driver of extinctions. With numerous competing extinction scenarios, and the realisation that some of the purported environmental stresses may once again be driving mass extinction, we explore how experimental biology might inform our understanding of ancient extinctions as well as future crises.
An understanding of the geological history and ecosystems evolution of Big Meadow Bog peatland at Brier Island, Nova Scotia is an important element of informing the conservation management of critical habitats for a complex of nationally listed, rare, disjunct wetland species. The ecology of the peatland is influenced by both chemistry and morphology of the bedrock and glacial sediments within the watershed. The Big Meadow Bog peatland is bordered to the north and south along its long axis by basaltic ridges of the North Mountain. Drainage from these watershed ridges flows to the peatland, which has both a northern and southern outflow to the sea. Paleogeographic reconstruction suggests that Brier Island was deglaciated sooner than the rest of southwestern Nova Scotia. Big Meadow Bog peatland contains a stratigraphic record of a late Holocene transition to a moister climate shortly after 3000 cal. BP. However, several periods of late Holocene drying took place from 1950 cal. BP until present, one of which is recorded stratigraphically by the presence of a conifer forest indicating significant lowering of the local water table. Under these conditions, both wetland productivity and water table varied considerably. When designing potential habitat preservation and restoration strategies, these site-specific records of moisture and habitat structure variability need to be considered. Specific sites in the Brier Island peatlands may respond very differently to particular restoration strategies aimed at establishing long-term residency of threatened and endangered species at wetland sites.
Polyphase fault evolution through reactivation is a globally observed phenomenon on passive margins. These structures play a crucial role in petroleum systems, offer vital constraints on rift and passive margin kinematics, and, in certain instances, serve as global markers for far-field stresses. Despite the significance of reactivated faults, understanding their kinematic evolution, existence, extent, and interactions within fault populations is often limited. This underscores the need for comprehensive investigations, including considerations of halokinesis in this process. This study presents a structural interpretation of a relay ramp identified in the Penobscot 3D seismic reflection survey offshore Nova Scotia, Canada. The ramp is characterized by two major SSE-dipping faults accompanied by smaller antithetic and synthetic normal faults with a general ENE-WSW strike. The two major faults exhibit evidence of reverse deformation in their lower sections, transitioning to normal offsets in their upper portions. Smaller faults predominantly affect younger strata without evidence of reactivation. Fault throw analysis indicates coupled movement on the main faults during both reverse and normal deformation intervals. Structural analysis suggests that these structures initially formed as reverse faults due to halokinesis and were subsequently reactivated during oceanward salt migration. The timing of Atlantic margin halokinesis aligns broadly with previously documented large-scale kinematic reorganization periods, suggesting similar kinematic events triggered salt movements in the Penobscot area. The observed kinematic dichotomy at depth is crucial, highlighting the potential oversight of polyphase deformation in areas where seismic data only captures near-surface structures. Recognising salt's role in kinematic reactivation is vital, explaining inversion phenomena and generating economically important trapping structures globally. This study implies that reactivation of structures in passive margins may be more widespread than previously acknowledged, particularly if seismic data only captures upper portions of structures.
The End-Triassic Mass Extinction (ETME) saw the catastrophic loss of ca. 50% of marine genera temporally associated with emplacement of the Central Atlantic Magmatic Province (CAMP). However, the effects of the ETME on land is a controversial topic. Evaluation of the disparate cause(s) and effects of the extinction requires additional, detailed terrestrial records of these events. Here, we present a multidisciplinary record of volcanism and environmental change from an expanded Triassic-Jurassic (T-J) transition preserved in lacustrine sediments from the Jiyuan Basin, North China. High-resolution chemostratigraphy, palynological, kerogen, and sedimentological data reveal that terrestrial conditions responded to and were defined by large-scale volcanism. The record of sedimentary mercury reveals two discrete CAMP eruptive phases during the T-J transition. Each of these can be correlated with large, negative C isotope excursions (CIE-I of −4.7‰; CIE-II of −2.9‰), significantly reduced plant diversity (with ca. 45 and 44% generic losses, respectively), enhanced wildfire (marked by increased fusinite or charcoal content), and major climatic shifts toward drier and hotter conditions (indicated by the occurrence of calcareous nodules, increased Classopollis pollen content, and PCA analysis). Our results show that CAMP eruptions may have followed a bimodal eruptive model and demonstrate the powerful ability of large-scale volcanism to alter the global C cycle and profoundly affect the climate, in turn leading to enhanced wildfires and a collapse in land plant diversity during the T-J transition.
A large dyke of quartz tholeiitic gabbronorite has been mapped for 59 km in southern New Brunswick, Canada, between Lepreau River in the northeast and Indian Island in the southwest. Scattered outcrops occur along a positive aeromagnetic lineament, providing a dyke strike of N42°E overall (segments N30°E to N72°E), dips of 80° to 90°NNW, and widths of 4 to 30 m. A new ⁴⁰Ar/³⁹Ar plagioclase age of 201.67 ± 0.35 Ma for the Lepreau River Dyke is similar to dates for the massive North Mountain Basalt in the Fundy Basin to the east. The dyke is associated with the Ministers Island and Christmas Cove dykes, which are indistinguishable in chemistry, petrology, and probable age, and we regard them as segments of the same co-magmatic dyke system. In addition, their petrology is similar to that of the basalts of the adjacent Early Mesozoic Fundy and Grand Manan basins. We propose that the Lepreau River and associated dykes were sources for the regional basin basalts, which in turn are part of the Central Atlantic Magmatic Province (CAMP) that overlaps the Triassic–Jurassic boundary and associated mass extinction event.
There is an apparent temporal correlation between large igneous province (LIP) emplacement and global environmental crises, including mass extinctions. Advances in the precision and accuracy of geochronology in the past decade have significantly improved estimates of the timing and duration of LIP emplacement, mass extinction events, and global climate perturbations, and in general have supported a temporal link between them. In this chapter, we review available geochronology of LIPs and of global extinction or climate events. We begin with an overview of the methodological advances permitting improved precision and accuracy in LIP geochronology. We then review the characteristics and geochronology of 12 LIP/event couplets from the past 700 Ma of Earth history, comparing the relative timing of magmatism and global change, and assessing the chronologic support for LIPs playing a causal role in Earth's climatic and biotic crises. We find that (1) improved geochronology in the last decade has shown that nearly all well‐dated LIPs erupted in < 1 Ma, irrespective of tectonic setting; (2) for well‐dated LIPs with correspondingly well‐dated mass extinctions, the LIPs began several hundred ka prior to a relatively short duration extinction event; and (3) for LIPs with a convincing temporal connection to mass extinctions, there seems to be no single characteristic that makes a LIP deadly. Despite much progress, higher precision geochronology of both eruptive and intrusive LIP events and better chronologies from extinction and climate proxy records will be required to further understand how these catastrophic volcanic events have changed the course of our planet's surface evolution.
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 Late Triassic (Carnian to Rhaetian Stages: ca. 237–201 Ma) has a long history of geological research, although controversy remains over the precise definition of key sub-unit boundaries, including those defining the three constituent stages. Within this context, at least five terrestrial bolide impact structures ranging from 9 to 85 km in diameter have been identified at present-day northern latitudes, the proximal remnant crater aspects of which have been studied in increasing detail over the last few decades. The more elusive distal sedimentary expressions of these multi-sized hypervelocity events remain largely unknown, although if preserved, identified and interpreted correctly, may (as precisely dateable event horizons) help to address certain existing stratigraphic uncertainties, particularly pertaining to the (longest) Norian Stage. Detailed absolute age-dating using a range of radioisotopic methods (e.g. U-Pb and 40Ar/39Ar) currently indicates that at least three of the confirmed Late Triassic impact craters formed prior to commencement of the major Rhaetian Central Atlantic Magmatic Province (CAMP) volcanic episode by several million years. Impact research efforts to date have focused mainly on describing and process modeling the relatively well-preserved largest impact structure, Manicouagan (215.5 Ma; 85 km diameter) located in northeastern Quebec, Canada and, to a lesser extent, the Saint Martin (227.8 Ma; 40 km) and Rochechouart (ca. 207–201 Ma; ca. 23–50 km) structures in central Manitoba, Canada and west-central France respectively. The smaller, subsurface Red Wing structure (ca. 200 Ma; 9 km diameter, ca. 2.5 km burial depth) located in South Dakota, USA, also has attracted significant economic interest. Unlike the well-documented End Cretaceous Chicxulub impact (66 Ma; ca. 180 Km), attempts to establish a globally significant causal extinction connection between the larger impacts (e.g. Manicouagan and Rochechouart) and Late Triassic marine and terrestrial bioevents, culminating with the ‘End Triassic Extinction’ (ETE), have essentially proved unsuccessful.
The Upper Triassic chronostratigraphic scale consists of one Series, the Upper Triassic, divided into three stages (in ascending order)—Carnian, Norian and Rhaetian. Only the base of the Carnian currently has an agreed on GSSP (global boundary stratotype section and point), though agreement on GSSPs for the bases of the Norian and Rhaetian is imminent. Substages of the Carnian and Norian provide more detailed subdivisions of Late Triassic time than do the relatively long Carnian and Norian stages. These substages need boundary definitions and greater use in Late Triassic correlations. Numerical chronology of the Late Triassic is based on very few radioisotopic ages from volcanic ash beds directly related to marine biostratigraphy. The numerical calibration of the Late Triassic favored here is Carnian ~220–237 Ma, Norian ~205–220 Ma and Rhaetian ~201–205 Ma. Late Triassic magnetostratigraphy is fraught with problems because the most complete record from the Newark Supergroup of eastern North America cannot be correlated based on pattern matching to any co-eval magnetostratigraphy from a marine section. The long Norian (beginning at ~228 Ma) was created by magnetostratigraphic correlations that abandoned biostratigraphic constraints and has produced extensive miscorrelation, particularly of nonmarine Carnian strata. A reliable Late Triassic magnetostratigraphy is a succession of multichrons that identifies the Carnian-early Norian and late Norian-Rhaetian as dominantly of normal polarity. Late Triassic cyclostratigraphy of the Newark Supergroup has been advanced as a floating astrochronology of the Late Triassic, but is problematic given evident hiatuses in the Newark record and the presence of non-cyclical lithofacies. Isotope stratigraphy of the Late Triassic, for example the late Rhaetian carbon-isotope excursion, has great potential for use in Late Triassic correlations. The Late Triassic timescale is still very much a work in progress that needs more precise chronostratigraphic definitions, additional numerical ages directly related to marine biostratigraphy, a wholesale rethinking of magnetostratigraphic correlations and additional cyclostratigraphic and isotopic data to achieve greater precision and stability.
Amygdaloidal basaltic flows of the Ashfield Formation were encountered in two drill holes in areas of positive aeromagnetic anomalies in the Carboniferous River Denys Basin in southwestern Cape Breton Island, Nova Scotia. One sample of medium-grained basalt yielded a plateau age of 201.8 ± 2.0 Ma, similar to the U-Pb and ⁴⁰Ar/³⁹Ar crystallization ages from basaltic flows and dykes in the Newark Supergroup. A second sample of zeolite-bearing basalt yielded a discordant age spectrum and a younger age of ca. 190 Ma, which is interpreted to date a widespread hydrothermal event related to zeolite formation. Whole-rock chemical data show that the Ashfield Formation basalt is low-Ti continental tholeiite, consistent with its withinplate tectonic setting. Chemically, it resembles basaltic flows in the Mesozoic Fundy and Grand Manan basins exposed in southern Nova Scotia and eastern New Brunswick and elsewhere in Central Atlantic Magmatic Province (CAMP). The age and geochemical data from the Ashfield Formation provide the first evidence for early Mesozoic CAMP volcanism in Cape Breton Island and demonstrate that the event was more widespread in Nova Scotia than previously thought, which has implications for its continuity and extent elsewhere within CAMP.
Orbitally controlled, sedimentary cycles of the Newark Supergroup permit pal-yniferous Late Triassic sections to be calibrated in time. Carnian palynofloras from · the Richmond basin exhibit 2-m.y. fluctuations in the spore/pollen ratio, but taxo-nomic composition remains stable. Diversity of Norian and Rhaetian palynofloras increases prior to a 60% reduction at the Triassic/Jurassic boundary. The extinction of Late Triassic palynomorph species is coincident with a spike in the spore/pollen ratio and approximately synchronous with the last appearances of tetrapod taxa and ichnofossil genera. This geologically brief episode of biotic turnover is consistent with bolide impact hypotheses.
The Triassic-Jurassic (Tr-J) boundary marks one of the five largest mass extinctions in the past 0.5 b.y. In many of the exposed rift basins of the Atlantic passive margin of eastern North America and Morocco, the boundary is identified as an interval of stratigraphically abrupt floral and faunal change within cyclical lacustrine sequences. A comparatively thin interval of Jurassic strata separates the boundary from extensive overlying basalt flows, the best dates of which (ca. 202 Ma) are practically indistinguishable from recent dates on tuffs from marine Tr-J boundary sequences. The pattern and magnitude of the Tr-J boundary at many sections spanning more than 10° of paleolatitude in eastern North America and Morocco are remarkably similar to those at the Cretaceous-Tertiary boundary, sparking much debate on the cause of the end-Triassic extinctions, hypotheses focusing on bolide impacts and climatic changes associated with flood basalt volcanism. Four prior attempts at finding evidence of impacts at the Tr-J boundary in these rift basin localities were unsuccessful. However, after more detailed sampling, a modest Ir anomaly has been reported (up to 285 ppt, 0.29 ng/g) in the Newark rift basin (New York, New Jersey, Pennsylvania, United States), and this anomaly is directly associated with a fern spike. A search for shocked quartz in these rift basins has thus far been fruitless. Although both the microstratigraphy and the biotic pattern of the boundary are very similar to continental Cretaceous-Tertiary boundary sections in the western United States, we cannot completely rule out a volcanic, or other nonimpact, hypothesis using data currently available.
The Newark Supergroup of Eastern North America consists of rocks judged to range in age from early Middle Triassic through late Early Jurassic. Dating is principally based on the recognition of seven pa-lynological zones correlated with the European standard stages and on correlation of vertebrates and megafossil plants. The basic floristic trends are a decrease in diversity into the Early Jurassic and the rise to strong dominance of the cheirolepidaceous conifers. Based on publish-ed radiometric scales, the Newark depositional episode lasted roughly 45 million years and was antecedent to the actual separation of the North American and African Plates. Correlation of other Early Mesozoic continental areas with the Newark allows the conclusions that there was a shift from Late Triassic floral and faunal provinciality to Early Jurassic homogeneity, and that this shift was synchronous with a widening of the equatorial arid zone. RESUMEN El Supergrupo Newark, del Oriente de America del Norte, consiste en rocas q u e a juicio de 10s autores tienen un margen de edad entre el ~ r i a s i c o Medio temprano y el Jurasico Temprano tardlo. La asignaci6n de edad se basa principalmente en el reconocimiento de siete zonas palino-logicas que se correlacionan con 10s pisos estandar europeos y en la correlation mediante vertebrados y megafosiles vegetales. Las tenden-cias floristicas basicas son un decrement0 de la diversidad hacia el Jurasico Temprano y el surgimiento a una dominancia fuerte de las coni-feras del tipo Cheirolepidiaceae. De acuerdo con escalas radiom6tricas publicadas, el episodic de deposit0 Newark dur6 unos 45 millones de aiios y precedi6 la separaci6n de las placas de ~ m 6 r i c a del Norte y de Africa. La correlaci6n de otras areas continentales del Mesozoico tem-prano con el Newark permite las conclusiones de qua en este lapso suce-di6 un cambio que a partir de la provincialidad de flora y fauna del Triasico Tardio llev6 a la homogeneidad del Jurasico Temprano, y que este cambio fue contemporsneo con el ensanchamiento de la zona arida ecuatorial.
Recent discoveries of palynoflorules at numerous localities in the Newark Group basins of the eastern United States provide new evidence for correlation of deposits in these basins. Floras from the Shuttle Meadow and Portland Formations of the Newark Group rocks in the Hartford Basin of Connecticut and Massachusetts indicate that the Triassic‐Jurassic boundary is located within the rocks of this basin: a shift of Corollina from more than 90% C. meyeriana to more than 90% C. torosus occurs somewhere between the Shuttle Meadow and Portland Formations and generally indicates a Rhaeto‐Liassic age. In the Shuttle Meadow Formation, the overall shape of the palynoflora (particularly the presence of Convolutispora klukiforma), associated fish, paleomagnetic data, and radiometric dates, as well as megafossil evidence of Brachyphyllum scotii and Clathropteris menis‐coides, support a basal Liassic age for this formation. Reptilean evidence in older strata of the Hartford Basin suggests that the Triassic‐Jurassic boundary may lie just below the Shuttle Meadow Formation. In addition the Portland Formation contains a palynomorph association clearly favoring early to middle Liassic age. Comparisons are made on the basis of studies of recently discovered Newark Group palynoflorules of early Liassic age from Virginia and of Carnian‐Norian age from New Jersey. Paleobotanical and geological evidence is summarized, showing that the predominantly Corollina (Hirmerella) palynofloras of the Hartford Basin were associated with a warm, seasonally wet and dry climate, and casting doubt on the idea that Corollina‐producing plants composed a swamp association within the original basin. Twenty‐seven genera and 42 species are described, as are 1 spore and 1 pollen type of uncertain taxonomic position. Eight new species are described: Camerosporites reductiverrucatus n. sp., Corollina murphyi n. sp., Cycadopites andrewsii n. sp., Cycadopites durhamensis n. sp., Cycadopites west‐fieldicus n. sp., Dictyophyllidites paramuensteri n. sp., Foveosporites agawa mensis n. sp., Verrucosisporites cheneyi n. sp.Six new combinations are proposed: Araucariacites punctatus (Nilsson) comb. nov., Callialasporites segmentatus (Balme) comb. nov., Corollina itunensis (Pocock) comb. nov., Corollina simplex (Danzé‐Corsin & Laveine) comb. nov., Cycadopites reticulatus (Nilsson) comb, nov., Granulatisporites infirmus (Balme) comb. nov.The genera Circulina and Corollina are formally emended, as are the species Corollina torosus (Reissinger) Klaus and Circulina simplex Malyavkina.
To determine whether the ~200 Ma central Atlantic magmatic province (CAMP) coincides with a normal polarity bias and a purported abrupt change in polar wander at the J1 cusp, we collected samples for paleomagnetic study from 80 sites distributed over a ~2500-m-thick section of sedimentary units that are interbedded with and overlie CAMP lavas in the Hartford basin, which together represent the initial 2.4 Ma of the Jurassic according to cycle stratigraphic analysis. Characteristic directions carried by hematite were isolated by thermal demagnetization in 71 sites and define a coherent magnetostratigraphy supported by a positive reversal test and an interbasin fold test. Despite a pronounced overall normal polarity bias (only three relatively short reverse polarity intervals could be confirmed in the sampled section), normal polarity Chron H24n that encompasses the CAMP extrusive zone is no more than 1.6 Ma in duration. Elongation/inclination analysis of the 315 characteristic directions, which have a flattened distribution, produces a result in agreement with a published mean direction for the CAMP volcanic units as well as published results similarly corrected for inclination error from the Newark basin. The three data sets (CAMP volcanics, Newark corrected sediments, and Hartford corrected sediments) provide a 201 Ma reference pole for eastern North America at 67.0°N, 93.8°E, A 95 = 3.2°. Paleopoles from the Moenave and Wingate formations from the Colorado Plateau that virtually define the J1 cusp can be brought into agreement with the 201 Ma reference pole with corrections for net clockwise rotation of the plateau relative to eastern North America and presumed sedimentary inclination error. The corrected data show that apparent polar wander for North America proceeds directly toward higher latitudes over the Late Triassic and Early Jurassic with no obvious change that can be associated with CAMP.
The evolution of life on Earth is marked by catastrophic extinction events, one of which occurred ca. 200 Ma at the transition from the Triassic Period to the Jurassic Period (Tr-J boundary), apparently contemporaneous with the eruption of the world's largest known continental igneous province, the Central Atlantic magmatic province. The temporal relationship of the Tr-J boundary and the province's volcanism is clarified by new multidisciplinary (stratigraphic, palynologic, geochronologic, paleomagnetic, geochemical) data that demonstrate that development of the Central Atlantic magmatic province straddled the Tr-J boundary and thus may have had a causal relationship with the climatic crisis and biotic turnover demarcating the boundary.
Most mass extinctions are linked with carbon isotope excursions, implying that biotic crises are coupled with changes in the global carbon cycle. The isotopic evolution during the end-Triassic extinction is far less documented than that for the other major Phanerozoic extinctions. Here we report a sharp and short-lived -3.50/00 excursion in carbon isotope values for carbonate (delta13Ccarb) corresponding to a -20/00 excursion in the isotopic composition of marine organic matter (delta13Corg) and other geochemical changes from the topmost Triassic in the Csovár section in Hungary. The Triassic- Jurassic boundary is defined by ammonoid and conodont biostratigraphy in a marine limestone sequence. A decline in primary productivity, release of methane through dissociation of gas hydrates, or a combination of the two may account for the correlative biotic and isotopic events.
A long core (1110 m) drilled at Montcornet (northeastern Paris Basin) provides early Jurassic magnetostratigraphic data coupled with biochronological control. About 600 paleomagnetic samples were obtained from a 148-m-thick series of Hettangian and Sinemurian rocks. A composite demagnetization using thermal (up to 300°C) followed by alternating field technique (up to 100 mT) is used to separate the magnetic components. A low unblocking temperature component (<250°C) with an inclination of about 65° is interpreted as a present-day field overprint. The characteristic remanent component with both normal and reversed antipodal directions is then isolated between 5 and 70 mT. Eighty-one polarity intervals are recognized in this study. The higher reversal frequency of the late Hettangian/early Sinemurian time interval contrasts with a lower reversal rate observed in the rest of the early Liassic. A rough mean estimate of about 5 reversals/m.y. can be proposed for the earliest Jurassic. These results represent a significant contribution to the magnetic polarity reversal timescale for a time interval hitherto poorly known and add to the magnetic reversal frequency curve of the last 350 m.y.
We present an integrated geomagnetic polarity and stratigraphic time scale for the Triassic, Jurassic, and Cretaceous periods of the Mesozoic Era, with age estimates and uncertainty limits for stage boundaries. The time scale uses a suite of 324 radiometric dates, including high-resolution Ar-40/Ar-39 age estimates. This framework involves the observed ties between (1) radiometric dates, biozones, and stage boundaries, and (2) between biozones and magnetic reversals on the seafloor and in sediments. Interpolation techniques include maximum likelihood estimation, smoothing cubic spline fitting, and magnetochronology. The age estimates for the 31 stage boundaries (in mega-annum) with uncertainty (millions of years) to 2 standard deviations, and the duration of the preceding stages (in parentheses) are Maastrichtian/Danian (Cretaceous/-Cenozoic) is 65.0 +/- 0.1 Ma (6.3 m.y.), Campanian/Maastrichtian is 71.3 +/- 0.5 Ma (12.2 m.y.), Santonian/Campanian is 83.5 +/- 0.5 Ma (2.3 m.y.), Coniacian/Santonian is 85.8 +/- 0.5 Ma (3.2 m.y.), Turonian/Coniacian is 89.0 +/- 0.5 Ma (4.5 m.y.), Cenomanina/Turonian is 93.5 +/- 0.2 Ma (5.4 m.y.), Albian/Cenomanian is 98.9 +/- 0.6 Ma (13.3 m.y.), Aptian/Albian is 112.2 +/- 1.1 Ma (8.8 m.y.), Barremian/Aptian is 121.0 +/- 1.4 Ma (6.0 m.y.), Hauterivian/Barremian is 127.0 +/- 1.6 Ma (5.0 m.y.), Valanginian/Hauterivian is 132.0 +/- 1.9 Ma (5.0 m.y., Berriasian/Valanginian is 137.0 +/- 2.2 Ma (7.2 m.y.), Tithonian/Berriasian (Jurassic/Cretaceous) is 144.2 +/- 2.6 Ma (6.5 m.y.), Kimmeridgian/Tithonian is 150.7 +/- 3.0 Ma (3.4 m.y.), Oxfordian/Kimmeridgian is 154.1 +/- 3.2 Ma (5.3 m.y.), Callovian/Oxfordian is 159.4 +/- 3.6 Ma (5.0 m.y.), Bathonian/Callovian is 164.4 +/- 3.8 Ma (4.8 m.y.), Bajocian/Bathonian is 169.2 +/- 4.0 Ma (7.3 m.y.), Aalenian/Bajocian is 176.5 +/- 4.0 Ma (3.6 m.y.), Toarcian/Aalenian is 180.1 +/- 4.0 Ma (9.5 m.y.), Sinemurian/Pliensbachian is 195.3 +/- 3.9 Ma (6.6 m.y.), Hettangian/Sinemurian is 201.9 +/- 3.9 Ma (3.8 m.y.), Rhaetian/Hettangian (Triassic/Jurassic) is 205.7 +/- 4.0 Ma (3.9 m.y.), Norian/Rhaetian is 209.6 +/- 4.1 Ma (11.1 m.y.), Carnian/Norian is 220.7 +/- 4.4 Ma (6.7 m.y.), Ladinian/Carnian is 227.4 +/- 4.5 Ma (6.9 m.y.), Anisian/Ladinian is 234.3 +/- 4.6 Ma (7.4 m.y.), Olenekian/Anisian is 241.7 +/- 4.7 Ma (3.1 m.y.), Induan/Olenekian is 244.8 +/- 4.8 Ma (3.4 m.y.), Tatarian/Induan (Permian/Triassic) is 248.2 +/- 4.8 Ma. The uncertainty in the relative duration of each individual stage is much less than the uncertainties on the ages of the stage boundaries.
Cycle stratigraphic and magnetostratigraphic analyses of a ~5000-m-thick composite section obtained by scientific coring in the Newark rift basin of eastern North America provide a high-resolution astronomically calibrated geomagnetic polarity timescale (GPTS) spanning over 30 m.y. of the Late Triassic and earliest Jurassic. Only normal polarity is found in ~1000 m of interbedded volcanics and continental sediments of earliest Jurassic age but a total of 59 normal and reverse polarity magnetozones are delineated in the underlying 4000+ m of Late Triassic continental sediments. Lithologic facies response to climatically induced lake level variation provides a full spectrum of Milankovitch cyclicity; the prominent 404 kyr orbital eccentricity climate cycle has a mean thickness of about 60 m and is the basis for scaling most of the stratigraphic section in time. When indexed to available radioisotopic dating, the resulting astronomically calibrated GPTS spans from the 202 Ma Triassic/Jurassic boundary to 233 Ma. Results of detailed sampling profiles across 42 magnetozone boundaries representing 35 different polarity reversals indicate transition durations that average 7.9 kyr, comparable to the estimated duration of recent polarity reversals. The polarity intervals have a mean duration of 0.53 m.y. with a corresponding reversal rate of 1.88 m.y.-1 and no significant polarity bias and are closely approximated by an exponential distribution with a gamma index k indistinguishable from 1. The longest polarity interval is about 2 m.y., and the shortest is about 0.02 m.y. The overall statistical properties indicate that the behavior of the geomagnetic field in the Late Triassic was not very different from that in the Cenozoic. This geomagnetic polarity record of the Late Triassic provides a well-dated chronostratigraphic framework suitable for detailed global correlation.
The biodiversity crisis at the end of the Triassic (Triassic-Jurassic boundary: TJB) has long been identified as one of the "big five" mass extinctions of the Phanerozoic. Attribution of this level of suddenness and severity to the TJB extinction began with Sepkoski (1982), who, based on a global compilation of families of marine invertebrates, designated the TJB extinction as one of four mass extinctions events of intermediate magnitude (end-Cretaceous, end-Triassic, Late Devonian, Late Ordovician), less severe than the largest Phanerozoic extinction, which was at the end of the Permian. This identification of a severe and sudden biotic decline at the TJB remained unquestioned until recently (Hallam 2002; Tanner et al. 2004; Lucas and Tanner 2004). Here, we review the magnitude and timing of the extinctions that took place during the Late Triassic. Our thesis is that the Late Triassic was an interval of elevated extinction rates and low origination rates that manifested themselves in a series of discrete extinctions during Carnian, Norian and Rhaetian time. Significantly, no reliable data exist to document global Late Triassic mass extinction(s) of many significant biotic groups, including foraminiferans, ostracods, gastropods, fishes and marine reptiles (Hallam 2002; Tanner et al. 2004). Therefore, we focus our discussion on those groups that have been perceived by some as part of a TJB mass extinction, namely radiolarians, marine bivalves, ammonoids, reefbuilding organisms, conodonts, land plants and terrestrial tetrapods (amphibians and reptiles).
The Triassic – Jurassic boundary is generally considered as one of the major extinctions in the history of Phanerozoic. The high-resolution ammonite correlations and carbon isotope marine record in the New York Canyon area allow to distinguish two negative carbon excursions across this boundary with different paleoenvironmental meanings. The Late Rhaetian negative excursion is related to the extinction and regressive phase. The Early Hettangian d 13 C org negative excursion is associated with a major floristic turnover and major ammonite and radiolarian radiation. The end-Triassic extinction – Early Jurassic recovery is fully compatible with a volcanism-triggered crisis, probably related to the Central Atlantic Magmatic Province. The main environmental stress might have been generated by repeated release of SO 2 gas, heavy metals emissions, darkening, and subsequent cooling. This phase was followed by a major long-term CO 2 accumulation during the Early Hettangian with development of nutrient-rich marine waters favouring the recovery of productivity and deposition of black shales. D 2004 Elsevier B.V. All rights reserved.
1] The Triassic-Jurassic boundary mass-extinction event (T-J; 199.6 Ma) is associated with major perturbations in the carbon cycle recorded in stable carbon isotopes. Two rapid negative isotope excursions in bulk organic carbon (d 13 C org) occur within the immediate boundary interval at multiple locations and have been linked to the outgassing of 12 C-enriched CO 2 from the Central Atlantic Magmatic Province. In British Columbia, a positive d 13 C org excursion of +5% (Vienna Peedee belemnite (V-PDB)) spans part or all of the subsequent Hettangian stage. Here, we examine the significance of these carbon isotope excursions as records of global carbon cycle dynamics across the T-J boundary and test the link between carbon cycle perturbation-stabilization and biotic extinction-recovery patterns. A combination of d 13 C org and palynological analyses from the Late Triassic to Early Jurassic in the Mingolsheim core (Germany) suggests that organic carbon isotope variations are best explained as the result of both compositional changes in terrestrial versus marine input and disturbance and recovery patterns of major terrestrial plant groups across the T-J boundary. A new high-resolution d 13 C carb record from the Val Adrara section in the Southern Alps (Italy) spanning from the uppermost Rhaetian through Lower Sinemurian does not exhibit a negative excursion at the T-J boundary but does record a large positive d 13 C carb excursion of +4% (V-PDB) in bulk carbonate that begins at the T-J boundary and reaches a local maximum at the Early Late Hettangian boundary. Values then gradually decrease reaching +0.
Formed as a major right-lateral fault zone during Paleozoic collisional orogenies and reactivated as a left-oblique system during the early Mesozoic, the east-striking Minas fault zone of Atlantic Canada controlled adjacent sedimentation in the Fundy rift basin, producing a series of synsedimentary microbasins. Northeast-striking boundary faults of the Fundy basin underwent mostly early Mesozoic normal slip and are reactivated Paleozoic thrusts. The adjacent basin has a much thicker section, transverse folds, and synthetic rider blocks. Contrasts in structural and stratigraphic styles are a response to local deformation controlled by reactivated fault zones of differing orientation under consistent northwest-southeast early Mesozoic extension rather than responses to a sequence of changing stress patterns.
1] The experimentally determined relationship between atmospheric pCO 2 and plant stomata has been used to interpret large but transient changes in atmospheric composition, such as may have resulted from the eruptions of flood basalt. However, this relationship has not been tested in the field, i.e. in the vicinity of active volcanoes, to examine the specific effects of volcanogenic emissions. Moreover, the interpretation of paleoatmospheric pCO 2 from fossil stomatal data assumes that the stomatal response resulted solely from variation in pCO 2 and ignores the potential effect of outgassed SO 2 . We hypothesize that volcanogenic SO 2 also has a significant effect on leaf stomata and test this hypothesis by measuring the stomatal index of the common swordfern (Nephrolepis exaltata) in the plumes of the actively outgassing vents of Kilauea volcano. We find that, compared to control locations, stomatal index is lowest at sample sites in the plume of Halema'uma'u Crater, where concentrations of both CO 2 and SO 2 are much higher than background. However, sites located directly in the plume of Pu'u O'o, where SO 2 levels are high, but CO 2 levels are not, also yield low values of stomatal index. We propose that shifts in the stomatal index of fossil leaves may record transient atmospheric increases in both SO 2 and CO 2 , such as may be caused by eruptions of flood basalts. Calculations of pCO 2 based on stomatal frequency are likely to be exaggerated. Citation: Tanner, L. H., D. L. Smith, and A. Allan (2007), Stomatal response of swordfern to volcanogenic CO 2 and SO 2 from Kilauea volcano, Geophys. Res. Lett., 34, L15807, doi:10.1029/2007GL030320.
The St. Audrie's Bay section in west Somerset comprises the uppermost Mercia Mudstone Group, the Penarth Group and the basal Lias Group and includes a candidate Global Stratotype Section and Point for the base of the Jurassic. The magnetostratigraphy has been evaluated through 122 m of this section at 147 stratigraphic levels, which range in age from mid-Norian to earliest Hettangian. In red dolomitic mudstones, the remanence is carried predominantly by haematite, whereas in non-red lithologies, it is mostly carried by magnetite. The mean virtual geomagnetic poles fall near the mean Upper Triassic and Lower Jurassic apparent polar wander track and display the start of the northeast-directed track typical of the Jurassic. The magnetostratigraphy comprises nine major magnetozones, five of normal polarity and four reversed, together with several minor magnetozones. In the Mercia Mudstone Group, the 68 m of the Twyning Mudstone Formation examined includes three major normal magnetozones (SA2n, SA3n and SA4n) and the Blue Anchor Formation has predominantly reversed polarity (SA4r) except at its top, in the Williton Member. The Penarth Group and basal Lias Group have predominantly normal polarity (SA5 to SA6n) but short reversals occur within the Westbury Formation and at the base of the Lilstock Formation and the Lias Group (SA5r).
Palynological data from the Newark basin of the Newark Supergroup reveal a spike in the spore/pollen ratio at the Triassic/Jurassic boundary. This spore spike is coincident with a 60% regional extinction of the palynoflora and approximately synchronous with terrestrial vertebrate extinctions. Orbitally controlled sedimentary cycles allow stratigraphic sections to be calibrated in time, constraining the duration of the microfloral turnover to an interval of 21 ky. The geologically brief palynofloral break is similar to Cretaceous/Tertiary boundary fern spikes. These data support a Triassic/Jurassic boundary impact-extinction scenario.
Detailed pétrographie and geochemical analyses of samples collected from eight cores of the U.S. Army Corps of Engineers Passaic Tunnel project indicate that the three principal basalt formations of the early Mesozoic Newark basin in New Jersey are composed of multiple flow units that can be identified on the basis of physical and petrochemical criteria. The high-titanium, quartz-normative (HTQ) Orange Mountain Basalt (lowermost formation: at least three flow units) and high-iron and high-titanium, quartz-normative (HFTQ) Hook Mountain Basalt (uppermost formation: at least two flow units) include flows characterized by a limited range in composition and are indicative of eruptive cycles during which individual magma sources underwent little change in composition and were tapped repeatedly. In contrast, the wide chemical diversity of the flows in the Preakness Basalt (middle formation: possibly nine flow units) is indicative of a period of volcanism in which successive eruptions were derived either from (1) separate high-iron, quartz-normative (HFQ) and low-titanium, quartznormative (LTQ) parental magmas; or (2) an LTQ parent that changed composition during the eruptive interval. The HTQ composition and limited variability of the Orange Mountain Basalt indicate petrochemical correlation with the stratigraphically comparable Mount Zion Church (Culpeper basin, Virginia) and Talcott (Hartford basin, Connecticut) Basalts. The wide range in composition of the Preakness Basalt supports previous petrochemical correlation with the Hickory Grove and Sander Basalts of the Culpeper basin. The HFQ compositional type of the Preakness, Hickory Grove, and Sander Basalts is similar to the Holyoke Basalt of the Hartford basin (Connecticut and Massachusetts) and Deerfield Basalt of the Deerfield basin (Massachusetts). The HFTQ Hook Mountain Basalt is nearly identical to the stratigraphically comparable Hampden Basalt of the Hartford basin (Connecticut and Massachusetts) in both composition and limited degree of compositional variability. These new data and conclusions drawn from recent cyclostratigraphic investigations of the intercalated sedimentary strata from these basins define three nearly synchronous eruptive intervals for the Eastern North America (ENA) province from Virginia to Massachusetts. Volcanic interval I, which followed an extended period of sedimentation in the Culpeper, Newark, and Hartford basins, was marked by repeated production of exclusively HTQ-type basalt and involved parental magmas that did significantly change composition during the eruptive episode. Volcanic interval II, which followed a second, shorter period of basin sedimentation occurring throughout the province, began with eruption of the Hickory Grove Basalt in the Culpeper basin and, following a period of renewed terrestrial sedimentation in this basin, resumed with nearly simultaneous extrusion of HFQ-type basalt in all of the basins. In the northern basins (Hartford and Deerfield), where basalt eruption was uninterrupted by significant sedimentation, this interval involved only HFQ-type basalt. However, in the southern basins (Culpeper and Newark), where basalt production was interspersed with one or more periods of sedimentation, lavas defined a range of compositions, including LTQtype and other hybrid varieties. Volcanic interval III, which followed another significant period of sedimentation in the Newark and Hartford basins, involved production of exclusively HFTQ-type basalt from parental sources that underwent slight change in composition during the episode. The similarity of inferred parental magma compositions from Virginia to Massachusetts implies the effect of large-scale petrologie control on melt production. The time-composition relationships of the basalts indicate that the volcanic sequences of the ENA province were produced by episodic tapping of compositionally distinct parental sources that varied in the extent of volcanic production on both a regional and intrabasin scale.
Time series of global diversity and extinction intensity measured from data on stratigraphic ranges of marine animal genera show the impact of bio-events on the fauna of the world ocean. Measured extinction intensities vary greatly, from major mass extinctions that eradicated 39 to 82% of generic diversity to smaller events that had substantially less impact on the global fauna. Many of the smaller extinction events are clearly visible only after a series of filters are applied to the data. Still, most of these extinction events are also visible in a smaller set of data on marine families. Although many of the episodes of extinction seen in the global data are well known from detailed biostratigraphic investigations, some are unstudied and require focused attention for confirmation or refutation.
Early Mesozoic tholeiitic flood basalts of the Central Atlantic Magmatic
Province (CAMP) are interbedded throughout much of their extent with
cyclical lacustrine strata, allowing Milankovitch calibration of the
duration of the extrusive episode. This cyclostratigraphy extends from
the Newark basin of the northeastern US, where it was first worked out,
to Nova Scotia and Morocco and constrains the outcropping extrusive
event to less than 600 ky in duration, beginning roughly 20 ky after the
Triassic-Jurassic boundary, and to within one pollen and spore zone and
one vertebrate biochron. Based principally on the well-known Newark
astronomically calibrated magnetic polarity time scale with new
additions from the Hartford basin, the rather large scatter in recent
radiometric dates from across CAMP (>10 m.y. ), centering on about
˜200 m.y., is not likely to be real. Rather, the existing
paleomagnetic data from both intrusive and extrusive rocks suggest
emplacement of nearly all the CAMP within less than 3 m.y. of nearly
entirely normal polarity. The very few examples of reversed
magnetizations suggest that some CAMP activity probably occurred just
prior to the Triassic-Jurassic boundary. Published paleomagnetic and
40Ar/39Ar data from the Clubhouse Crossroads
Basalt are reviewed and with new paleomagnetic data suggest that
alteration and possible core misorientation could be responsible for the
apparent differences with the CAMP. The Clubhouse Crossroads Basalt at
the base of the Coastal Plain of South Carolina and Georgia provides a
link to the volumetrically massive volcanic wedge of seaward dipping
reflectors present in the subsurface off the southeastern US that may be
part of the same igneous event, suggesting that the CAMP marks the
formation of the oldest Atlantic oceanic crust.
During Early Jurassic time, the Scots Bay Formation accumulated in an aerobic lake on the floor of the subtropical Fundy rift valley. A diverse biota flourished in the lake as evidenced by algal stromatolites, oncolites, charophytes, ostracods, gastropods, conchostracans, fish bones, calcispheres and logs. Carbonate wackestone and packstone were deposited in the littoral zone and lime mudstone accumulated offshore on a proximal slope. Silica-rich hydrothermal springs and seeps around and on the floor of the lake precipitated siliceous tufa and silicified adjacent carbonate strata. The tufa is characterized by the progressive sequence: (1) open-framework, porous substrate of goethite spheres, (2) encrusting chalcedony spherulites where goethite inclusions decrease in size and number outwards towards the surfaces of the spherulites, (3) a fringe of quartz on the chalcedony spherulites and (4) coarsening inwards mosaics of quartz that filled the remaining voids. Carbonate diagenesis included conversion of low-Mg calcite ooze to micrite and microspar-pseudospar, and local dissolution and reprecipitation of calcite cement. At times the lake shrank in size, concentrating silica in increasingly alkaline lake water which then silicified some of the carbonate strata and logs. The latest cements were calcite, zeolites and celadonite.
The mass extinction at the Triassic-Jurassic (Tr-J) boundary at 200 Ma ranks amongst the five most extreme in the Phanerozoic and occurred approximately at the same time as one of the largest volcanic episodes known from the geological record, that which characterized the Central Atlantic Magmatic Province (CAMP). Interpretations of climate change across the boundary are contradictory, whilst changes in the carbon cycle are poorly constrained. Here we present new organic carbon isotope data that demonstrate that changes in flora and fauna from both terrestrial and marine environments occurred synchronously with a transient light-carbon-isotope excursion and that this happened significantly earlier than the conventionally established marine Tr-J boundary. A second negative carbon-isotope excursion dominated the shallow-marine and atmospheric reservoirs for at least 600 k.y. These data suggest that a major perturbation occurred in the global carbon cycle at the Tr-J boundary which resulted in a significant increase in atmospheric pCO2 in less than a million years. Our results indicate synchroneity between the carbon-isotope excursion, the extinction event, the eruption of the first CAMP lavas, suggesting a causal link between loss of terrestrial and marine taxa and the very earliest eruptive phases.
We are very pleased with the attention, long overdue, that the Triassic–Jurassic boundary and associated events, such as the CAMP, are receiving. This can only lead to greater specificity of hypotheses and greater understanding in the long run, and it is worth emphasizing some broad areas of agreement. Marzoli et al. (2008-this volume) points out the closeness in time of CAMP and Tr–J extinctions, and on this we all agree. We also agree that the systematic differences among different isotopic systems used for dating is a challenge to determining the relative timing of events dated with different techniques. This problem, however, seem to be fading as high-precision single-crystal U–Pb dates (206Pb/238U) are available from a variety of tuffs interbedded with marine strata as well as the North Mountain Basalt of Nova Scotia, which lies above the palynological Triassic–Jurassic extinction event in Nova Scotia. Schoene et al. (2006) obtained an age of 201.27 ± 0.03 Ma from this basalt, which is very close to an age of 201.5 Ma for a tuff 1 m above the last local occurrence of the topmost Triassic guide-fossil, the ammonite Choristoceras in a marine section in Peru (Schaltegger et al., 2007), presumably very close to the Triassic–Jurassic extinction event. Schaltegger et al. (2007) also obtained an age of 199.5 Ma for the Hettangian–Sinemurian boundary from the latter section. Consistent with these ages, Pálfy and Mundil (2006) obtained ages of 200.6 ± 0.3 Ma for an ash layer in ammonite-bearing Middle Hettangian marine sediments in, Alaska, and 198.0 ± 0.6 Ma for a tuff layer in Early Sinemurian sediments in Hungary. These dates are not compatible with the multi-crystal age for the Triassic–Jurassic boundary of 199.6 ± 0.3 Ma of Pálfy and Mundil (2006), a fact recognized by Pálfy and Mundil (2006). Thus, we are in complete agreement that the Triassic–Jurassic extinction event is extremely close in time to the onset of the CAMP. The question is, “are any of the known flows of the CAMP actually at or before this extinction event?”. That is the key issue dealt with by Whiteside et al. (2007), and it is a possibility that we recognize as completely plausible, but not yet demonstrated. It is in that spirit of general agreement that we reply to Marzoli et al.'s, comment. We note, however, that their comment touches on far too many points to adequately address in this reply, and we chose to focus our response on their most substantive issues, recalling that our paper was focusing on the testable aspects of their overall hypothesis. We deal with their criticisms in the order they present them.
This study represents a contribution to the developing knowledge about the microfloristic provincialism affecting Upper Triassic palynoflora. The compositional differences existing between the Onslow and the Ipswich microfloras are mainly based on the presence, in the Onslow microflora, of a diverse and more varied group of gymnosperm pollen grains, including typical European elements. In this study, the palynological assemblages recovered from Carnian successions of the western Tethyan margin (Sicily, Tunisia, Albany, Libya and Israel) are compared with those of West Timor microfloral assemblages, which have been referred to the Onslow microflora of southern hemisphere. They contain several common taxa, mainly consisting of conifer miospores widely recorded in Carnian European successions and less frequently recovered in the Carnian of western and eastern Australia. The number of Circum-Mediterranean sporomorphs in the Onslow microflora assemblages is wider than previously thought, providing new evidences to extend the distribution of the Onslow microflora to include Carnian associations formerly assigned to the Circum-Mediterranean assemblages. These broad microfloral affinities seem to indicate the existence of a homogeneous microflora that maintains, with minor variations, its composition from western Tethys coasts to the northern Australian margin (West Timor). The parent plant community grew in a coastal environment, along the continental margins; the establishment of an equable climatic regime influenced by warm equatorial currents and suitable humid conditions probably conditioned its diffusion. It has long been recognised that the strong floral provinciality which characterised the Late Triassic world gave way to a more homogeneous flora in the Early Jurassic. The decrease in macrofloral diversity is associated with a less pronounced microfloristic provincialism, which in turn coincides with the rise, to strong dominance, of cheirolepidiaceous conifers (Circumpolles producers). This important microfloristic event occurs in the southern hemisphere during the Early Jurassic, however this study reveals their incipient diffusion during the Norian.
The detailed palynostratigraphy established for basins of the Newark Supergroup south of the Canadian border has proven inapplicable to the oxidized, palynologically barren outcrops typical of the Fundy basin of the Maritime Provinces. Dating of the Fundy stratigraphic section has thus been based on lithostratigraphic correlations, radiometric dates, and rare palynomorphs. Palynofloral assemblages recently recovered from an outcrop of the uppermost Blomidon Formation in the Nova Scotia arm of the Fundy basin permit the first correlations with Triassic/Jurassic boundary palynofloras throughout the Newark Supergroup.The well-preserved palynofloras are all dominated by the genus Corollina, but examination of the less common elements indicates that only those assemblages at the top of the Blomidon Formation, immediately below the North Mountain Basalt, are of Early Jurassic age. These palynofloras contain species that are also present in earliest Jurassic assemblages from the Hartford basin. Palynomorph assemblages 30 cm downsection from the basalt contain rare specimens of the Late Triassic index species Patinasporites densus and an array of monosulcate grains correlative with late Rhaetian assemblages from the Newark basin. Three new monosulcate species (Cycadopites ginker, C. tattoo, and C. schlischii) are described herein.
The North Mountain Basalt (NMB) is a sequence of continental tholeiitc basalts that are part of the larger, 200 Ma Central Atlantic Magmatic Province (CAMP).The NMB occur within the Fundy Basin, one of several Mesozoic extensional basins that formed during the incipient rupture of Pangea. In addition to the NMB, the Fundy Basin was also filled by fluvial, alluvial, playa, lacustrine and aeolian sediments under arid to semi-arid conditions. Mapping of a 200 km long segment of the NMB along the southern coast of the Bay of Fundy indicates for the first time the lateral continuity of the three recognized lava units, the East Ferry, Margaretsville and Brier Island members (EFM, MM, BIM, respectively), that comprise the NMB. The EFM (150 m) are massive and characterized by pervasive development of columnar jointing, both colonnade and entablature. In addition, whereas the EFM contains abundant layers of mafic pegmatite, the BIM is characterized by abundant mesostasis, possibly reflecting widespread quenching of this flow, and locally abundant segregation pipes due to mobilization of a late-stage felsic liquid. These two units represent expansive eruption of low viscoity flows onto a low slope surface, which encouraged uniform thickness and their massive nature, but the role of faulted basins cannot be ruled out. In contrast, the MM (170 m) consists of numerous (>16) inflated pahoehoe sheet flow lobes. Evidence that these flows formed as pahoehoe flows is represented by exceptional development of the vesicle zonation (i.e., upper crust, vesicle sheets, vesicle cylinders, pipe vesicles) as observed in modern Hawaiian flows, historical Icelandic flows and ancient flows of the Columbia River Basalt Group. The thickness of upper crust zones indicates that the individual flows formed over months to years, whereas inclined basal pipe vesicles indicate the MM and BIM flowed to the south. The similar age and nature of the NMB to other basalt sequences in CAMP suggest that similar processes operated throughout this LIP, thereby having implications for such phenomena as atmospheric contamination and extinction events caused by eruption of these voluminous basaltic lava flows.
Important sources of systematic error in 40Ar/39Ar dating arise from uncertainties in the 40K decay constants and K/Ar isotopic data for neutron fluence monitors (standards). The activity data underlying the decay constants used in geochronology since 1977 are more dispersed than acknowledged by previous geochronologically oriented summaries, and compilations of essentially the same data in nuclear physics and chemistry literature since 1973 have consistently produced lower estimates (and larger assigned uncertainties) of the constants for 40K → 40Ar and 40K → 40Ca decay. Considering also uncertainties in 40K/K, and the questionable existence of a γ-less electron capture 40K → 40Ar decay direct to ground state, the total 40K decay constant is known to no better than ±2% at the 2σ level.40Ar∗/40K ratios for individual standards are known to better than ±2% in some cases, but interlaboratory discrepancies of more than 2% in the 40Ar/39Ar ages of secondary standards like the Fish Canyon sanidine (FCs) suggest larger uncertainties.
The present paper provides a palynological analysis of samples from the “Kössener Schichten”, “Schattwalder Schichten” and the ammonoid (Psiloceras planorbe)-bearing beds of the “Fleckenmergel/Fleckenkalk” found in the vicinity of Salzburg (Austria and adjacent part of Germany).It is shown that the compositional development of latest Triassic—earliest Jurassic palynological assemblages from Alpine sequences matches the situation in the Germanic realm. A characteristic phase in this development is interpreted in terms of the Rhaetipollis germanicus Assemblage Zone. It is considered that this zone could well be regarded as a palynological characterization of the Rhaetian Stage in Europe and North America.Although palynology does not support the Rhaetian concept based on the occurrence of the species Choristoceras marshi exclusively, the traditional ammonoid-based Triassic—Jurassic boundary can be palynologically recognized.
New precise zircon U–Pb ages are proposed for the Triassic–Jurassic (Rhetian–Hettangian) and the Hettangian–Sinemurian boundaries. The ages were obtained by ID-TIMS dating of single chemical-abraded zircons from volcanic ash layers within the Pucara Group, Aramachay Formation in the Utcubamba valley, northern Peru. Ash layers situated between last and first occurrences of boundary-defining ammonites yielded 206 Pb/ 238 U ages of 201.58 ± 0.17/0.28 Ma (95% c.l., uncertainties without/with decay constant errors, respectively) for the Triassic– Jurassic and of 199.53 ± 0.19 / 0.29 Ma for the Hettangian–Sinemurian boundaries. The former is established on a tuff located 1 m above the last local occurrence of the topmost Triassic genus Choristoceras, and 5 m below the Hettangian genus Psiloceras. The latter sample was obtained from a tuff collected within the Badouxia canadensis beds. Our new ages document total duration of the Hettagian of no more than c. 2 m.y., which has fundamental implications for the interpretation and significance of the ammonite recovery after the topmost Triassic extinction. The U–Pb age is about 0.8 ± 0.5% older than 40 Ar– 39 Ar dates determined on flood basalts of the Central Atlantic Magmatic Province (CAMP). Given the widely accepted hypothesis that inaccuracies in the 40 K decay constants or physical constants create a similar bias between the two dating methods, our new U–Pb zircon age determination for the T/J boundary corroborates the hypothesis that the CAMP was emplaced at the same time and may be responsible for a major climatic turnover and mass extinction. The zircon 206 Pb/ 238 U age for the T/J boundary is marginally older than the North Mountain Basalt (Newark Supergroup, Nova Scotia, Canada), which has been dated at 201.27 ± 0.06 Ma [Schoene et al., 2006. Geochim. Cosmochim. Acta 70, 426–445]. It will be important to look for older eruptions of the CAMP and date them precisely by U–Pb techniques while addressing all sources of systematic uncertainty to further test the hypothesis of volcanic induced climate change leading to extinction. Such high-precision, high-accuracy data will be instrumental for constraining the contemporaneity of geological events at a 100 kyr level.
1. The camp and the T–J boundary The interpretation and significance of events at the Triassic– Jurassic (T–J) boundary are investigated in numerous research papers (e.g. those recently published in a special volume of this journal; Hesselbo et al., 2007), and are still matter of considerable scientific debate. The end of the Triassic is characterized by a major biotic turnover (Tanner et al., 2004) that may have been caused, at least in part, by the volcanic activity of the CAMP (Central Atlantic magmatic province). Such a scenario is broadly compatible with the short duration and 40 Ar/ 39 Ar age of the peak activity of the CAMP (199.1± 1.0 Ma; Knight et al., 2004; Nomade et al., 2007; Verati et al., 2007), which is comparable in age to the present best understanding of the U/Pb age of the marine T–J boundary (199.6 ± 0.3 Ma; Pàlfy et al., 2000), as well as with observed shifts of C and Os isotopes in marine sediments across the boundary (e.g., Beerling and Berner, 2002; Cohen and Coe, 2002; Hesselbo et al., 2002). A more robust determination of the relative timing of the CAMP magmatism and the T–J boundary mass extinction, however, is presently hindered by two primary challenges. First, analytical ages of the CAMP and the T–J boundary have been determined via different radioisotopic systems which are not yet well intercalibrated and analytical uncertainties of the isotopic ages are larger than the probable duration of the peak volcanic activity. The apparent synchrony of the ages of the boundary (determined by U/Pb) and the peak of CAMP volcanism (determined by 40 Ar/ 39 Ar) combined with the increasingly well established ca. 1% bias between current calibrations of the two systems (e.g. Min et al., 2000) might suggest that CAMP inception actually predated the boundary by ca. 2 Ma. However, it appears likely that the 199.6 ± 0.3 Ma U/Pb age reported by Pálfy et al. (2000) is slightly too young due to unmitigated Pb-loss (Mundil et al., 2005), thus temporal coincidence of the two events remains possible. Secondly, CAMP lava flows are preserved in continental basins only, whereas definition of the T–J boundary is based on marine biotic events (e.g., ammonite turnover). The correlation of volcanism and T–J boundary is therefore based on magnetostratigraphic correla-tions (e.g., Hounslow et al., 2004) combined with multidisciplin-ary stratigraphic studies of continental basins flooded by CAMP lavas, where the T–J boundary is defined through palynology. The paper by Whiteside et al. (2007) focuses on the relative timing of the T–J boundary mass extinction and the CAMP
More than 20 successions containing the Triassic–Jurassic (T–J) boundary were studied in five of the major geological units of Spain. The data are from outcrop, cored boreholes, and interpreted well-logs. A consistent − 3.4‰ δ13Corg isotope excursion, starting in the Rhaetian and continuing in the Hettangian, was recorded in Asturias. Climate changes in the T–J transition show a warming episode in the early Hettangian. Other climate changes are indicated by an increase in hygrophytic miospores above the T–J boundary; this reflects a more humid episode at the beginning of the Hettangian. The Messejana Dyke in southeastern Iberia is part of the Central Atlantic Magmatic Province (CAMP). CO2 outgassing related to extensive magmatic activity in the CAMP is thought to be one of the possible factors responsible for the end-Triassic mass extinction. No major sea-level changes or unconformities were recorded at the T–J boundary. Only in the Asturias area was there a well-defined shallow carbonate platform during the T–J transition. The other areas of eastern and northern Spain were occupied by coastal playas and sabkhas that developed in arid climatic conditions. The biotic crisis around the T–J boundary is reflected in the palynomorph record. In Asturias, seven species do not persist beyond the late Rhaetian, and only six appeared in the Triassic–Jurassic transition. However, 22 taxa appeared in the early Hettangian.
Review of sea-level changes during the big five mass extinctions and several lesser extinction events reveals that the majority coincide with large eustatic inflexions. The degree of certainty with which these eustatic oscillations are known varies considerably. Thus, the late Ordovician and end Cretaceous extinctions are associated with unequivocal, major regressions demonstrated from numerous, widespread regions. In contrast, the multiple, high frequency sea-level changes Ž . reported for the Frasnian–Famennian crisis based on the supposed depth-preferences of conodont taxa have little support from sequence stratigraphic analyses, which reveals the interval to be one of highstand. The end Permian mass extinction has w long been related to a severe, first order lowstand of sea level Newell, N.D., 1967. Revolutions in the history of life. Geol. x Soc. Am. Spec. Pap. 89, 63–91. based primarily on the widespread absence of latest Permian ammonoid markers, but field evidence reveals that the interval coincides with a major transgression. Newell's hypothesis that marine extinctions are related to shelf habitat loss during severe regression remains tenable for the end Guadalupian and end Triassic extinction events but not for other crises. Rapid high amplitude regressive–transgressive couplets are the most frequently observed eustatic changes at times of mass extinction, with the majority of extinctions occurring during the transgressive pulse when anoxic bottom waters often became extensive. The ultimate cause of the sea-level changes is generally unclear. A glacioeustatic driving mechanism can only be convincingly demonstrated for the end Ordovician and end Devonian events. Ž . At other times, it is speculated that they may relate to the widespread regional doming and subsequent collapse caused by Ž . the impingement of superplumes and ultimate eruption on the base of the lithosphere. q 1999 Elsevier Science B.V. All rights reserved.
Stable isotope analyses of Late Triassic to earliest Jurassic strata from Kennecott Point in the Queen Charlotte Islands, British Columbia, Canada shows the presence of two distinct and different organic carbon isotope anomalies at the Norian/Rhaetian and Rhaetian/Hettangian (=Triassic/Jurassic) stage boundaries. At the older of these boundaries, which is marked by the disappearance of the bivalve Monotis, the isotope record shows a series of short-lived positive excursions toward heavier values. Strata approaching this boundary show evidence of increasing anoxia. At the higher boundary, marked by the disappearance of the last remaining Triassic ammonites and over 50 species of radiolarians, the isotopic pattern consists of a series of short duration negative anomalies. The two events, separated by the duration of the Rhaetian age, comprise the end-Triassic mass extinction. While there is no definitive evidence as to cause, the isotopic record does not appear similar to that of the impact-caused Cretaceous/Tertiary boundary extinction.
The McCoy Brook Formation is a 230+ m sequence of redbeds of Early Jurassic age that accumulated in the subtropical Fundy rift basin. The basin was asymmetrical, bordered on the northern side by the Cobequid fault system and adjacent highlands. The formation is a mosaic of terrestrial facies. (a) Multi- and single-storey fluvial sandstones were deposited by rivers that collected drainage from the norhern highlands, and flowed southwest across the valley floor. (b) Graded-bed sequences of sandstone → mudstone were deposited by flood events on the fluvial floodplains and the margins of playas. (c) Interbedded sandstones and finely laminated to disrupted red mudstones represent deposits of interfingering sandflats at the toes of alluvial fans and playas, respectively. The fabrics of both lithologies are commonly disrupted by desiccation and intrastratal precipitation of calcite and minor gypsum. (d) Plane-bedded conglomerate and pebbly sandstone record deposition in shallow channels that traversed alluvial fans. (e) Non-bedded breccias of basalt boulders up to 8 m in size in a sand to mud matrix formed as talus against palaeocliffs of the Lower Jurassic North Mountain Basalt. The palaeocliffs resulted from synsedimentary faulting within the basin. (f) Basalt conglomerate beds with matrix- to clast-supported fabrics comprise sequences deposited by debris-flows, probably generated by remobilization of talus. (g) A thin sequence of limestone, siltstone, and muddy sandstone containing fish scales and bones formed in a shallow lake on a basalt flow. (h) Sandstones containing m-scale crossbeds and a three-fold hierarchy of erosional surfaces accumulated as barchans and barchanoid transverse ridges that moved southwest in the valley.
The Triassic–Jurassic boundary is generally considered as one of the major extinctions in the history of Phanerozoic. The high-resolution ammonite correlations and carbon isotope marine record in the New York Canyon area allow to distinguish two negative carbon excursions across this boundary with different paleoenvironmental meanings. The Late Rhaetian negative excursion is related to the extinction and regressive phase. The Early Hettangian δ13Corg negative excursion is associated with a major floristic turnover and major ammonite and radiolarian radiation.The end-Triassic extinction–Early Jurassic recovery is fully compatible with a volcanism-triggered crisis, probably related to the Central Atlantic Magmatic Province. The main environmental stress might have been generated by repeated release of SO2 gas, heavy metals emissions, darkening, and subsequent cooling. This phase was followed by a major long-term CO2 accumulation during the Early Hettangian with development of nutrient-rich marine waters favouring the recovery of productivity and deposition of black shales.
The end-Triassic was marked by one of the five important Phanerozoic global mass extinctions. The construction of a detailed magnetic polarity time scale for this period, that would integrate data from marine and terrestrial realms, is thus of particular interest. We report new magnetostratigraphic data from the Oyuklu section located in southwestern Turkey, which allow one to propose a complete late Upper Norian (Sevatian 2) to Rhaetian magnetic polarity sequence. Two correlations are discussed between the new Tethyan marine sequence and the (continental) magnetic polarity record previously determined from the Newark basin in eastern North America. Both options suggest that the Rhaetian is at least partly missing in the Newark basin, which would reconcile most Late Triassic magnetostratigraphic results and biotic features obtained from marine and continental environments. Following our preferred correlation, the Rhaetian would have a duration as short as ∼ 2 Myr, and ∼ 4.5 Myr if the Sevatian 2 zone is included as part of the Rhaetian.
A detailed 40Ar/39Ar study, of mineral separates from the Jurassic Atlantic Continental Tholeiites (JACT) of Guyana (French Guyana and Surinam, South America), and Guinea (West Africa) related to the initial opening of the Central Atlantic, has been carried out. In French Guyana, plateau ages of 196.0 ± 5.7 Ma and 196.1 ± 7.5 Ma were obtained on single, small amphibole grains from NNW—SSE trending dykes. In Guinea, single biotite grains from intrusive formations from the Kakoulima and Fouta Djalon areas yielded plateau ages of 200.4 ± 0.2 Ma and 194.8 ± 0.5 Ma, concordant with high temperature apparent ages on other biotites. The bulk plagioclase samples display disturbed age spectra due to alteration and excess argon. However, intermediate temperature, weighted mean plagioclase ages are similar in both regions of Guyana and Guinea, ranging from 200.2 ± 2.4 Ma to 188.7 ± 1.9 Ma, partly in agreement with the amphibole and biotite data.These data, combined with previous 40Ar/39Ar and U/Pb results from the northern part of the Central Atlantic margins, indicate intense magmatic activity distributed over a large area from Iberia to Liberia (ca. 4500 km long) for a short period of time (204-195 Ma, perhaps less for the bulk of the magmatism) during the initial break-up of Pangea continent. These data do not support an initiation of the magmatism from a radial volcano-tectonic system centred in the south of the region, as suggested by May [1], and the initial break-up seems to affect the whole Central Atlantic during a period of 9 Ma.
The Central Atlantic Magmatic Province (CAMP) is the world's largest known continental igneous province and is contemporaneous with the Triassic–Jurassic (T–J) boundary that marks one of the five largest biological extinctions in the last 600 Ma. Although constraints on the duration of the CAMP volcanism remain yet poorly defined, the assumption that the CAMP may have had a causal relationship with the climatic and biotic crisis was suggested [Marzoli, A., Bertrand, H., Knight, K., Cirilli, S., Buratti, N, Verati, C., Nomade, S., Renne, P.R., Youbi, N., Martini, R., Allenbach, K., Neuwerth, R., Rapaille, C., Zaninetti, L., Bellieni, G., 2004. Synchrony of the Central Atlantic magmatic province and the Triassic–Jurassic boundary climatic and biotic crisis. Geology 32, 973–976.]. In this paper, we present new 40Ar/39Ar ages on basaltic flows from Moroccan (central High Atlas, Oujda and Argana) and Portuguese (Algarve and Santiago do Cacém) basins where CAMP lava flows are interlayered with T–J sedimentary sequences.
There is a wide range of geochemical, sedimentological and palaeontological evidence suggesting that the interval at the end of the Triassic and the beginning of the Jurassic, some 200 Ma ago, was a time of major environmental change. The supercontinent Pangaea began to rift, eustatic sea-level rose, and there was a mass extinction in marine and terrestrial biota. The eruption of at least ∼ 3 × 106 km3 of basaltic lavas that comprise the Central Atlantic Magmatic Province (CAMP) also took place at that time and was intimately associated with the onset of rifting of Pangaea. Emplacement of this Large Igneous Province occurred within a relatively very short period of perhaps no more than ∼ 1 Ma. Although relatively little of CAMP now remains, the original province was extremely large, extending from present-day Nova Scotia to Bolivia and from central southern USA to Morocco. Of major relevance to the environmental impact of the CAMP was its relatively rapid emplacement and its original location across the equator. Recent advances in our understanding of the weathering of silicate rocks, and in particular of fresh basaltic rocks, have highlighted the importance of the weathering process in influencing environmental change. In this contribution we examine the details of the seawater Sr- and Os-isotope records that span the Triassic–Jurassic boundary in order to understand the nature and course of environmental change at that time. Correlation of Sr-isotope data from mainland Europe and the UK shows that the rapid rate of decrease in the 87Sr/86Sr ratio of seawater, which had started in the Early Rhaetian (Late Triassic), came to an end in the Late Rhaetian close to the Triassic–Jurassic boundary. At that time, the 187Os/188Os ratio of seawater had also decreased to particularly low values. In the Late Rhaetian, the seawater 87Sr/86Sr ratio rapidly increased from ∼ 0.70765 to ∼ 0.70775, and then it and the seawater 187Os/188Os ratio both remained approximately constant for the duration of the Hettangian (the first ∼ 3 Ma of the Jurassic). Apart from a transient excursion to radiogenic Os-isotope values (i.e. high 187Os/188Os ratios) near the Triassic–Jurassic boundary, the unradiogenic 187Os/188Os ratio of seawater during the Hettangian is interpreted as reflecting a major perturbation to global weathering patterns that was caused by the rapid weathering and erosion of the CAMP immediately after its emplacement. We suggest that the rapid increase of seawater 87Sr/86Sr ratios in the Late Rhaetian and the approximately constant 87Sr/86Sr ratios throughout the Hettangian were caused by the input of a large amount of additional radiogenic Sr to the oceans, which was likely to have been derived from a readily-weathered lithology such as carbonate or evaporite. At the start of the Sinemurian, the 87Sr/86Sr ratio of seawater began to decrease while at the same time the 187Os/188Os ratio of seawater increased to more radiogenic values. We interpret the trends in the seawater Sr- and Os-isotope compositions at the start of the Sinemurian as evidence that much of the CAMP had been removed by chemical weathering, by which time the CAMP had ceased to have a major influence on Earth's environment.The patterns of change in the seawater Sr- and Os-isotope records that occurred in the latest Triassic and earliest Jurassic show many similarities with those that took place in the Pliensbachian–Toarcian ∼ 183 Ma ago, overlapping the eruption of the Karoo–Ferrar igneous province. In both cases, the seawater Sr- and Os-isotope records indicate that there was a relatively very brief interval during which rates of continental weathering increased greatly. The similarities in the responses of the seawater Sr- and Os-isotope records at those times strongly suggest that the eruption and subsequent erosion of basaltic Large Igneous Provinces have played a major role in defining the course of environmental change in the past.
New precise zircon U–Pb ages are proposed for the Triassic–Jurassic (Rhetian–Hettangian) and the Hettangian–Sinemurian boundaries. The ages were obtained by ID-TIMS dating of single chemical-abraded zircons from volcanic ash layers within the Pucara Group, Aramachay Formation in the Utcubamba valley, northern Peru. Ash layers situated between last and first occurrences of boundary-defining ammonites yielded 206Pb/238U ages of 201.58 ± 0.17/0.28 Ma (95% c.l., uncertainties without/with decay constant errors, respectively) for the Triassic–Jurassic and of 199.53 ± 0.19 / 0.29 Ma for the Hettangian–Sinemurian boundaries. The former is established on a tuff located 1 m above the last local occurrence of the topmost Triassic genus Choristoceras, and 5 m below the Hettangian genus Psiloceras. The latter sample was obtained from a tuff collected within the Badouxia canadensis beds. Our new ages document total duration of the Hettagian of no more than c. 2 m.y., which has fundamental implications for the interpretation and significance of the ammonite recovery after the topmost Triassic extinction.