Abstract Radiolarians have been used to determine geological ages and have contributed markedly to our understanding of Earth’s history. Hydrofluoric acid (HF) has traditionally been used to extract ...radiolarian fossils from siliceous deposits (i.e., radiolarian cherts), but this acid is strictly regulated because of environmental and human health concerns. Here we report on the successful extraction of radiolarians from cherts using a low-concentration NaOH solution (1 mol/L NaOH) as an alternative to HF. The degree of chert dissolution in NaOH is strongly temperature-dependent and is limited at < 80 °C. However, even a 1 mol/L NaOH solution is sufficient to dissolve chert at 100 °C. Our new NaOH method yields better-preserved radiolarian fossils compared with the conventional HF method. The 1 mol/L NaOH solution is less hazardous, easier to handle, and has fewer effects on the environment and human health than HF. Therefore, this method can be widely used for research and teaching purposes in studies of radiolarian fossils, even in institutions where HF cannot be used owing to chemical restrictions.
The Norian and Rhaetian transition (Late Triassic) is characterized by a faunal turnover in major pelagic groups, such as radiolarians, conodonts, and ammonoids. Although catastrophic events such as ...emplacements of large igneous provinces and/or extraterrestrial impacts have been suggested to account for this biotic turnover, firm evidence based on geochemistry of sedimentary successions is still lacking. In order to assess environmental changes across the Norian/Rhaetian boundary (NRB), we report high–resolution stratigraphic variations for whole-rock major, trace, and highly siderophile element abundances, together with Re–Os isotope ratios for the Sasso di Castalda section in Lagonegro Basin, southern Italy. The section consists of a continuously exposed sequence of upper Norian (Sevatian) through the lower Rhaetian of a deep basinal deposits. Our data demonstrated that the upper Norian section records important events in stratigraphically ascending order: (1) a depositional environment moved below the Carbonate Compensation Depth, leading to the carbonate-biosilica transition associated with a slight depletion of elements favored in heavy minerals such as Zr, Hf, and Ti, (2) an input of Rochechouart impact components detected by platinum-group element anomaly, and (3) a transient change of redox state into low oxygen (dysoxic to suboxic) conditions marked by increases of V, U, and Re. This sequence of events suggests that the Rochechouart impact predates the major environmental changes resulting in faunal turnover at the NRB. Although their direct causal relationships are highly questionable given the small size of impactor and the interval between the impact horizon and the NRB, the possibility of triggering subsequent environmental and biotic collapses cannot be ruled out. This study provides the first identification of Rochechouart impact horizon in marine strata, which could be an important event marker for further studies on contemporaneous sections in the Lagonegro Basin and other localities.
•HSE abundances and Os isotopes determined for the Upper Triassic deposits in Italy.•Subsidence of the depositional sites with constant supply of terrigenous materials.•Rochechouart impact layer identified with PGE anomaly and Cr–Ir discrimination.•Enrichments of V, U and Re suggest low oxygen condition in the uppermost Norian.•The Rochechouart impact predates redox change and subsequent biotic turnover.
For the Upper Triassic, conodonts are the primary tools utilized in biostratigraphic investigations. For an effective biostratigraphic zonation, the species should be constrained by clear ...phylogenetic relationships, in which the stratigraphic ranges and taxonomy are reliable. Unfortunately, a phylogenetic framework for the Late Triassic pectiniform conodonts is almost missing, except for particular intervals, such as the Carnian/Norian boundary. The purpose of this study is to examine the latest Norian and Rhaetian pectiniform conodonts in detail in an attempt to determine their phylogenetic relationships, by applying novel phylogenetic methodologies that incorporate both morphological and stratigraphic data. This work is based on the conodont assemblages from the Upper Triassic strata of the Lagonegro Basin (southern Apennines, southern Italy) and the Csővár area (north-central Hungary), complemented with data from the literature. The calibrated phylogenetic analysis of the latest Norian and Rhaetian conodonts supports a two-step evolutionary history: a first radiation (~211–210 Ma) of the Parvigondolella species and the first representative of the genus Misikella, followed by a second phase (~206.5–205 Ma) leading to the final radiation of the Misikella species. Furthermore, the systematic revision of uppermost Triassic conodonts is provided along with the description of Misikella kolarae n. sp.
•Mockina bidentata: ancestor of clade Parvigondolella and clade Misikella•Two radiation phases in Late Norian-Rhaetian conodont evolution•Affinity of Misikella rhaetica with the Misikella clade is confirmed•Upper Sevatian and Rhaetian conodont zones subdivided into six subzones
Numerous stratiform manganese deposits occur in the Permian to Jurassic bedded chert successions of the Jurassic accretionary complexes of the Chichibu, Mino–Tamba, and North Kitakami belts in Japan. ...These accretionary complexes consist of deep-sea sediments accumulated in a pelagic, open-ocean setting within the Panthalassa Ocean. Although the depositional ages and processes of the Permian and Jurassic manganese deposits in these accretionary complexes have been studied, the Triassic bedded chert-hosted stratiform manganese deposits are poorly understood. We investigated the occurrence and stratigraphic distribution of Triassic stratiform manganese deposits in Japan, constraining their ages by means of integrated conodont–radiolarian biostratigraphy. On the basis of the conodont and radiolarian biostratigraphies, the depositional age of the Triassic manganese deposits was constrained to the latest Julian to earliest Tuvalian (mid-Carnian). This age indicates that the formation of the Triassic manganese deposits occurred contemporaneously with the last eruptive phase of the Wrangellia Large Igneous Province (LIP) volcanism and subsequent changes in the deep-sea redox conditions in the Panthalassa Ocean during the Carnian pluvial episode (CPE). Therefore, these manganese deposits may have been formed with the hydrothermal activity associated with the eruption of the Wrangellia LIP and/or the subsequent changes in marine redox conditions in the CPE.
•We examined Triassic Mn ore sections in Jurassic accretionary complexes, Japan.•Triassic Mn deposits occur in deep-sea chert sequences of the Panthalassa Ocean.•Radiolarians and conodonts constrain the age of the Mn deposits to mid-Carnian.•Mn deposits may have been formed by Wrangellia LIP volcanism and marine redox changes.
The Carnian Pluvial Episode (CPE) was a global environmental change and biotic crisis that occurred during the Carnian (Late Triassic). The climate during the CPE was characterized by a short-lived ...period of extreme rainfall, and an extinction of marine taxa is known to have occurred during the latest Julian (i.e. early Carnian). Although these events are considered to have been caused by the Wrangellia Flood Basalt (FB) volcanism, existing studies have found little direct evidence to support this. We investigated the temporal relationship between the eruption of Wrangellia FB and CPE using high-resolution microfossil biostratigraphy and paleo-seawater Os isotope data of an Upper Triassic bedded chert succession from an accretionary complex in Japan, which accumulated in a pelagic deep-sea environment in an equatorial region of the Panthalassa Ocean. Our biostratigraphic analysis, based on conodonts and radiolarians, and osmium isotope data show: (i) a continuous decline of initial Os isotope ratios (187Os/188Osi) in the early Julian; (ii) low 187Os/188Osi ratios during the late Julian; and (iii) an abrupt increase in 187Os/188Osi ratios at the end of the Julian. The decrease in 187Os/188Osi ratios throughout the Julian suggests an increased input of unradiogenic Os from the eruption of the Wrangellia FB into the ocean. Moreover, redox-sensitive elements, such as V and U, increased abruptly at the end of the Julian, which is the first evidence of reducing conditions during the CPE within the pelagic deep-sea Panthalassa Ocean. Marine anoxic event in the late Julian has been recognized from widespread deposition of black shales and organic-rich marls in intermediate to shallow water Tethyan sections. Thus, oxygen-depleted conditions occurred at the Tethyan shallow continental margin, as well as in the pelagic deep-sea Panthalassa Ocean, at the end of Wrangellia FB volcanism.
•An Os isotopic profile of the Carnian chert succession in Japan was determined.•Os isotope data indicate the Wrangellia LIP formed during the Julian.•Two negative δ13Corg shifts were detected in the Julian 2 in the study section.•Enrichment of redox-sensitive elements suggests oxygen-depleted conditions occurred in the Panthalassa in the Julian 2.
We investigated for magnetostratigraphy the Rio Nigra and Rio Frommer stratigraphic sections from Alpe di Siusi/Seiser Alm (Dolomites, northern Italy) in order to improve the calibration of the ...Triassic time scale. Both sections are characterized by ammonoid and conodont associations typical of Longobardian (late Ladinian, Middle Triassic) age. Moreover, the Rio Nigra section is constrained by a U-Pb zircon date of 237.77 ± 0.05 Ma. Building on the recently verified Newark-Hartford astrochronological polarity timescale for the Late Carnian–Rhaetian (plus the Hettangian) and through magnetostratigraphic correlations of an updated inventory of Tethyan marine stratigraphic sections from the literature, some of which are provided with U-Pb zircon age constraints, we propose a revised Geomagnetic Polarity Time Scale for the entire Triassic.
•New U-Pb constrained Ladinian magnetostratigraphy improves Triassic chronology.•Using recent magnetostratigraphic data to update the Geomagnetic Polarity Timescale•Updated Geomagnetic Polarity Timescale led to a duration of 50.5 Myr for Triassic.
We present a multi-proxy investigation of a lower Carnian basinal succession from Polzberg in the Northern Calcareous Alps (Lower Austria). A section comprising a unique Konservat-Lagerstätte was ...studied based on bio- and chemostratigraphy along with geophysical methods, yielding a detailed and robust stratigraphic calibration of the Polzberg succession. The Polzberg section revealed the paleoceanographic history and helped to identify a global climatic reversal, the Carnian Pluvial Episode. The age of the Upper Triassic Reingraben formation in the Northern Calcareous Alps is refined as the Austrotrachyceras austriacum Zone within the lower Carnian (Julian 2). Ammonoids and conodonts provide a detailed biostratigraphic subdivision that serves as a basis for analyses of the faunal distribution and the paleoenvironmental evolution of the Upper Triassic Reifling Basin. The succession includes lithological and facies changes similar to those of coeval units in the Tethys. The Carnian was characterized by a weak (~ 1‰) positive δ
C trend, punctuated by a negative shift during the lower Carnian corresponding to the initiation of the Carnian Pluvial Episode, a period representing the onset of early/late Carnian transitional global greenhouse conditions. Organic maturity parameters and the conodont alteration index (CAI) show that the thermal overprint of the Polzberg section is low. Biomarker proxies suggest that the organic matter of the uppermost Göstling formation is a mixture of marine and terrestrial material deposited in a dysoxic environment. Within the overlaying Reingraben formation, the amount of marine biomass decreased gradually upwards. Oxygen-depleted conditions, probably due to water-column stratification, continued during deposition of the Reingraben formation. Bacterial sulfate reduction played a major role in organic matter degradation.
The Carnian Pluvial Episode was a phase of global climatic change and biotic turnover that occurred during the early Late Triassic. In marine sedimentary basins, the arrival of huge amounts of ...siliciclastic sediments, the establishment of anoxic conditions, and a sudden change of the carbonate factory on platforms marked the Carnian Pluvial Episode. The sedimentary changes are closely associated with abrupt biological turnover among marine and terrestrial groups as, for example, an extinction among ammonoids and conodonts in the ocean, and a turnover of the vertebrate fauna and the flora on land. Multiple negative carbon-isotope excursions were recorded during the Carnian Pluvial Episode in both organic matter and marine carbonates, suggesting repeated injection of 13C-depleted CO2 into the ocean–atmosphere system, but their temporal and causal links with the sedimentological and palaeontological changes are poorly understood. We here review the existing carbon-isotope records and present new data on the carbon-isotope composition of organic carbon in selected sections of the western Tethys realm that record the entire Carnian Pluvial Episode. New ammonoid, conodont and sporomorph biostratigraphic data were collected and coupled to an extensive review of the existing biostratigraphy to constrain the age of the sampled sections. The results provide biostratigraphically constrained composite organic carbon-isotope curves for the Carnian, which sheds light on the temporal and causal links between the main carbon-isotope perturbations, and the distinct environmental and biotic changes that mark the Carnian Pluvial Episode. The carbon-isotope records suggest that a series of carbon-cycle perturbations, possibly recording multiple phases of volcanic activity during the emplacement of the Wrangellia Large Igneous Province, disrupted Carnian environments and ecosystems repeatedly over a remarkably long time interval of about 1 million years.
The objective of this study is to examine the evolution of all the braced patients diagnosed with early onset scoliosis in a private scoliosis center. All patients diagnosed with EOS and braced ...before the age of ten were retrospectively reviewed. The results have been defined in accordance with the Scoliosis Research Society (SRS) for bracing criteria, and with a minimum follow-up of one year. Improvement and stabilization were considered successful treatments, while failure was considered to be an unsuccessful treatment. Successful results were observed in 80% of patients (63% worst case). In the success group, the Cobb angle was reduced from 36.3° (21-68) to 25° (10-43), with 36% of patients being initially treated only with night-time bracing. Twenty percent of the patients failed, seven had more than 45° at the last control and five had undergone surgery. This study suggests that bracing, using a modern 3D-brace concept, could be an effective treatment option for early onset scoliosis and advocates exploring its effectiveness as an alternative to casting throughout studies of higher levels of evidence.
The Carnian Pluvial Episode (CPE) was a short interval of extreme rainfall in the Late Triassic that caused significant changes in marine ecosystems. Global warming induced by Wrangellia volcanism is ...thought to have resulted in oceanic anoxia during the CPE, but the global extent, duration, and severity of anoxia, and its effects on major marine taxa, remain unclear. To address this, we examined an equatorial record of conditions in the Panthalassa Ocean during the CPE, focusing on marine Os isotope data, redox conditions, and conodont and radiolarian biostratigraphy. The results show that Wrangellia volcanism peaked in the latest Julian (early Carnian), coinciding with development of reducing conditions in the deep-sea Panthalassa. A strong conodont turnover occurred during the period of oceanic anoxia, whereas radiolarians were less affected and their diversity increased after the recovery from anoxia. The increased radiolarian diversity during the early Tuvalian (late Carnian) can be attributed to chemical weathering and enhanced nutrient fluxes associated with global warming and the more humid climate of Pangea.
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