Geochemistry, zircon U-Pb geochronology and Sr-Nd-Hf isotopic composition of the Cha Val plutonic rocks in central Vietnam: Implications for Permian-Triassic Paleo-Tethys subduction-related magmatism

together with abundant Permian-Triassic magmatic rocks. This magmatic complex provides important information to reconstruct the tectonic evolution of the Indochina block and surrounding areas. The Cha Val plutonic rocks mainly comprise diorite, quartz diorite, and granodiorite. Geochemically, they are metaluminous with low A/CNK (0.49 to 1.16 with an average of 0.85), medium to high K, low to medium SiO2, and Na2O/K2O>1. Trace and rare earth element compositions display enrichment in Cs, U, Pb, and Nd, but depletion in Ba, Nb, Ta, P, Eu, and Ti, similar to those of continental arc-related magmas. Rock-forming minerals of the Cha Val plutonic rocks are characterized by abundant hornblende. All observed petrographical and geochemical characteristics suggest that the Cha Val plutonic rocks are typical for I-type affinity generated from a subduction regime. LA-ICP-MS U-Pb zircon analyses of three representative samples yielded their crystallization ages between 258.0 Ma and 248.9 Ma, temporally coeval with Late Permian-Early Triassic magmatism previously reported in the Truong Son belt. The (87Sr/86Sr)i ratios (0.7081 to 0.7244), negative whole-rock εNd(t) values (-4.5 to -2.9), zircon εHf(t) values (-1.04 to 2.71), and whole-rock Nd and zircon Hf model ages (TDM2) (1394 Ma to 1111 Ma) indicate that the Cha Val plutonic rocks are derived from melting of Mesoproterozoic crustal materials with a minor contribution of mantle-derived melt. Together with other Permian-Triassic magmatic complexes along the Song Ma suture zone and the Truong Son Belt, the Cha Val plutonic rocks are a representative of magmatism associated with the subduction-collision that amalgamated the South China and Indochina blocks after the closure of a branch of Paleo-Tethys along the Song Ma suture zone during the Late Permian-Early Triassic Indosinian orogeny.

Klisura/Rozino granite, Central Sredna Gora: a part of the story of late Permian–Early Triassic extensional magmatic event

Тhe late- to post-Variscan magmatic activity in the South Black See region took plaсe during a considerably long period of ca. 80 from Late Carboniferous up to Early–Mid Triassic as two episodes are distinguished. The obtained age of 253.6±1.6 Ma for the Klisura/Rozino granite gives further evidence of the contemporaneous intrusive and extrusive magmatism during late Permian and Early Triassic in the Sredna Gora and Balkan zones.

PT formation conditions of polymetallic ores from the Pb-Zn-Fe Aktash skarn deposit (Western Karamazar, Tajikistan)

Fluid inclusions are studied in calcite from magnetite ores and sulfde-carbonate veins of the Aktash sulfde-magnetite deposit (Western Karanazar, Tajikistan) to identify their formation conditions. The deposit is confned to a contact zone between carbonate (Upper Devonian–Lower Carboniferous dolomite and limestones) and intrusive rocks (Middle Carboniferous–Early Triassic granodiorites and porphyry granodiorites) of the Kansai ore feld. The fuid inclusion study showed that calcite of ore veins formed from moderately saline (4.4–10.8 wt. % NaCl-equiv.) aqueous Na-K ± Mg chloride fuids at a decreasing temperature from 300 to 160 °C. The homogenization temperatures of fuid inclusions are consistent with thermometric data for chlorite, which formed together with calcite (176–295 °C). Keywords: calcite, chlorite, formation conditions, fuid inclusions, polymetallic ores, magnetite ores, Aktash deposit, Western Karamazar.

A new phosphatized ophiuroid from the lower Triassic of Nevada and its position in the evolutionary history of the Ophiuroidea (Echinodermata)

The Lower Triassic fossil record of brittle stars is relatively rich, yet most records published to date are based on poorly preserved or insufficiently known fossils. This hampers exhaustive morphological analyses, comparison with recent relatives or inclusion of Early Triassic ophiuroid taxa in phylogenetic estimates. Here, we describe a new ophiuroid from the Lower Triassic of Nevada, preserved as phosphatized skeletal parts and assigned to the new taxon Ophiosuperstes praeparvus gen. et sp. nov Maxwell, V. & Pruss. S.B. This unusual preservation of the fossils allowed for acid-extraction of an entire suite of dissociated skeletal parts, including lateral arm plates, ventral arm plates, vertebrae and various disk plates, thus unlocking sufficient morphological information to explore the phylogenetic position of the new taxon. Bayesian phylogenetic inference suggests a basalmost position of O. praeparvus within the Ophintegrida, sister to all other sampled members of that superorder. The existence of coeval but more derived ophiuroids suggests that O. praeparvus probably represents a member of a more ancient stem ophintegrid group persisting into the Early Triassic.

Review of Triassic insects in China

Studies of Triassic insects in China began in 1956, and so far, a total of 89 genera and 109 species have been found from the Triassic of China. The fossil records are from 17 provinces (or regions) in China are assigned to 11 orders except for two genera and species considered incertae sedis in Insecta. These Chinese Triassic insects including one Early Triassic, 53 Middle Triassic and 55 Late Triassic species are briefly reviewed in taxonomy and distribution, and listed here with detailed taxonomic and stratigraphic information. The Middle Triassic Tongchuan Entomofauna and Late Triassic Toksun Entomofauna are introduced much detailed from the perspectives of composition and taxonomy. Existing data indicate that the Chinese Triassic entomofauna is dominated by Hemiptera, Mecoptera and Coleoptera; the Chinese Early Triassic insects are only known from Fuyuan in Yunnan Province, Middle Triassic ones mainly known from northern China and sporadically from Guizhou Province, southern China, and Late Triassic ones widely seen in both northern and southern China; and the Middle and Late Triassic entomofaunas are similar in abundance but show a pattern of “more in northern China than in southern China”.

A new faunistic component of the Lower Triassic Panchet Formation of India increases the continental non-archosauromorph neodiapsid record in the aftermath of the end-Permian mass extinction

The fossil record of Early Triassic diapsids is very important to understand how the end-Permian mass extinction affected ecosystems and the patterns and processes involved in the subsequent biotic recovery. Vertebrate fossil assemblages of continental deposits in current-day South Africa, China, and Russia are the best source of information of this clade during the aftermath of the extinction event. Although considerably less sampled, the Induan continental rocks of the Panchet Formation of the Damodar Basin (eastern India) have also yielded a relatively diverse vertebrate assemblage composed of fishes, temnospondyls, synapsids, and a single proterosuchid taxon. Here, we report on a small isolated diapsid partial ilium (ISIR 1132) from the upper Panchet Formation. This specimen has a distinct morphology compared to other tetrapods that we know, including a shallow emargination on the dorsal margin of the anterior portion of the iliac blade, and ratio between height of iliac blade versus maximum height of iliac acetabulum at level of the dorsalmost extension of supraacetabular crest ≤0.45. Comparisons and a quantitative phylogenetic analysis found ISIR 1132 as a non-archosauromorph neodiapsid. This new specimen expands the reptile diversity in the Panchet Formation as well as for the rest of Gondwana, where Early Triassic non-archosauromorph neodiapsid species are extremely scarce.

The Permian–Triassic boundary section at Baghuk Mountain, Central Iran: carbonate microfacies and depositional environment

Sections at Baghuk Mountain, 45 km NNW of Abadeh (Central Iran), have excellent exposures of fossiliferous marine Late Permian to Early Triassic sedimentary successions. Detailed bed-by-bed sampling enables the analysis of microfacies changes of three successive rock units across the Permian–Triassic boundary. The Late Permian Hambast Formation is mainly the result of biogenic carbonate production. Its carbonate microfacies is dominated by biogen-rich and bioturbated nodular limestones, indicating a well-oxygenated aphotic to dysphotic environment. The biogen-dominated carbonate factory in the Permian ceased simultaneously with the main mass extinction pulse, which is marked by a sharp contact between the Hambast-Formation and the overlaying Baghuk Member (= ‘Boundary Clay’). The clay and silt deposits of the Baghuk Member with some carbonate beds show only a few signs of bioturbation or relics of benthic communities. The Early Triassic Claraia Beds are characterised by a partly microbially induced carbonate production, which is indicated by frequent microbialite structures. The depositional environment does not provide evidence of large amplitude changes of sea level or subaerial exposure during the Permian–Triassic boundary interval. The deposition of the Baghuk Mountain sediments took place in a deep shelf environment, most of the time below the storm wave base.

Exceptional fossil assemblages confirm the existence of complex Early Triassic ecosystems during the early Spathian

The mass extinction characterizing the Permian/Triassic boundary (PTB; ~ 252 Ma) corresponds to a major faunal shift between the Palaeozoic and the Modern evolutionary fauna. The temporal, spatial, environmental, and ecological dynamics of the associated biotic recovery remain highly debated, partly due to the scarce, or poorly-known, Early Triassic fossil record. Recently, an exceptionally complex ecosystem dated from immediately after the Smithian/Spathian boundary (~ 3 myr after the PTB) was reported: the Paris Biota (Idaho, USA). However, the spatiotemporal representativeness of this unique assemblage remained questionable as it was hitherto only reported from a single site. Here we describe three new exceptionally diverse assemblages of the same age as the Paris Biota, and a fourth younger one. They are located in Idaho and Nevada, and are taxonomic subsets of the Paris Biota. We show that the latter covered a region-wide area and persisted at least partially throughout the Spathian. The presence of a well-established marine fauna such as the Paris Biota, as soon as the early Spathian, indicates that the post-PTB biotic recovery and the installation of complex ecosystems probably took place earlier than often assumed, at least at a regional scale.