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There are two Triassic vertebrate sites in Villány Hills (Southern Hungary), where productive and continuous excavations have been carried out in the last six years resulting in a rich and diversified assemblage of shallow marine to coastal animals. The studied formations belong to the Villány–Bihor Unit of the Tisza Megaunit, which was located at the passive margin of the European Plate during the Triassic. The relatively diverse vertebrate assemblage was collected from a Road-cut on Templom Hill and a newly discovered site at a construction zone located on the Somssich Hill. Four main lithofacies were identified and interpreted in the newly discovered Construction vertebrate site consisting of dolomite (deposited in a shallow, restricted lagoon environment), dolomarl (shallow marine sediments with enhanced terrigenous input), reddish silty claystone (paleosol) and sandstone (terrigenous provenance) indicating that the sediments of the Construction vertebrate site were formed in a subtidal to peritidal zone of the inner ramp environment, where the main controlling factor of the alternating sedimentation was the climate change. However, the recurring paleosol formation in the middle part of the section also indicates a rapid sea-level fall when the marine sediments were repeatedly exposed to subaerial conditions. In the Road-cut site the siliciclastic sediments of the Mészhegy Sandstone Formation are exposed, representing a nearshore, shallow marine environment characterized by high siliciclastic input from the mainland. [ABSTRACT FROM AUTHOR]

Magnetic, petrological and mineralogical data from 13 sites (99 independently oriented samples) of the Lower Triassic rocks located in the SW segment of the West Spitsbergen Fold and Thrust Belt (WSFTB) are presented in order to identify the ferrimagnetic carriers and establish the origin of the natural remanent magnetization (NRM). Volcanic lithoclasts and other detrital resistive grains in which the primary magnetization might endure are present in some samples. On the other hand, petrological studies indicate that sulphide remineralization could have had an important influence on the remagnetization of these rocks. The dominant ferrimagnetic carriers are titanomagnetite and magnetite. While the titanomagnetite may preserve the primary magnetization, the magnetite is a more likely potential carrier of secondary overprints. The complex NRM patterns found in most of the samples may be explained by the coexistence and partial overlapping of components representing different stages of magnetization. Components of both polarities were identified in the investigated material. The reversal test performed on the most stable components that demagnetized above 300°C proved to be negative at the 95% confidence level at any stage of unfolding. They are better grouped, however, after 100% tectonic corrections and the most stable components are clustered in high inclinations (c. 70–80°). This suggests that at least part of the measured palaeomagnetic vectors represent a secondary prefolding magnetic overprint that originated in post-Jurassic time before the WSFTB event. Vitrinite reflectance studies show these rocks have not been subjected to any strong heating (<200°C). [ABSTRACT FROM AUTHOR]

An ophiolitic mélange of Avala Mountain located south of Belgrade was studied to obtain age data from blocks of radiolarian cherts and to enable better understanding of age and nature of this mélange. The studied area is located south of Avala Mt. and its geotectonic position is rather obscure. The obtained data allow us to determine radiolarians from five samples; one is of Late Anisian to Early Ladinian, and four of them are of Middle Jurassic (Late Bathonian-Early Callovian) age. The finding of Triassic as well as Jurassic age radiolarians in one and the same mélange suggests that this mélange formed during obduction of the Western Vardar ophiolites. [ABSTRACT FROM AUTHOR]

Abstract Paraná Basin exposes two distinct portions from Triassic deposits bearing different clay minerals content. Even if they belong to Santa Maria Supersequence, both are commonly referred as Santa Maria Formation and Arroio Moirão Graben. These sedimentary layers were deposited in Triassic and separated later because of overall spreading in southern portion of Gondwana paleocontinent during Cretaceous, forming a relict graben to the southern part of Paraná basin. This process isolated the layers of Arroio Moirão Gráben from the well-known Santa Maria layers, even though they stratigraphically belong to the same unit. The deposits are part of Gondwana Supersequence II when the Paraná rift basin formed. Even in genetically-related rocks, clay minerals show different assemblages in each portion. In Santa Maria Formation rocks, clay minerals content represents arid to semi-arid climate, e.g., I/S mixed-layers and illite, whereas in Arroio Moirão Graben, clay minerals content is confined to kaolinite, which implies humid conditions. Differences in clay mineral assemblages for these sedimentary units exemplify distinct diagenetic or climate conditions. SMF has more influence from the arid conditions, while AMG has both climatic and diagenetic humid features in the clay content. Highlights • Clay mineral content from same age altered by multiple conditions. • Clay minerals as a reflection of paleoclimate conditions. • Telodiagenesis ability to change primary clay content. • Eodiagenesis vs. Telodiagenesis dynamic over fine fractions. [ABSTRACT FROM AUTHOR]

The paper presents the results of the petrographic and organic geochemical studies of a jet sample recovered from a Mid-Triassic carbonate succession from the West Balkan tectonic zone in Bulgaria. Total organic carbon contents (TOC=92 % daf) and high vitrinite reflectance (Ro=1.9 %) indicate semi-anthracite coalification rank. Very high Tmax (577 °C) and low HI (~10 mg HC/g TOC) further support the overmature organic matter. Extractable organic matter is characterized by high portions of NSO compounds and asphaltenes (>75 %). Hydrocarbons constitute about 20 % and are characterized by the predominance of the saturated hydrocarbons over the aromatics. n-Alkanes distribution, dominated by short-chain compounds (n-C17–18), is consistent with the woody origin of the jet and the thermal maturity of the organic matter. The predominance of PAHs with condensed structure over their alkylated isomers is considered to be a result of the complex reaction occurring within the organic matrix during the catagenesis, rather than to the presence of combustion-derived organic matter. Based on the distribution of the diterpenoids, a tentative identification of a possible Voltziales conifer family source is identified. Low Pr/Ph ratio (0.88) and aryl isoprenoids outline anoxic conditions of jet formation, whereas the presence of organic sulfur compounds and tri-MTTchroman suggest marine depositional environment with normal salinity. [ABSTRACT FROM AUTHOR]

It is proposed that unstable temperature conditions in the Late Wuchiapingian and Early Changhsingian (Late Permian) changed in the Boreal Superrealm to less contrasting climatic conditions in the Late Changhsingian and Early Induan (the formation time of trap formation of the Siberian Platform), with a stable trend of increasing temperature in the Early Triassic. The problem of the absence of signs of mass extinction of marine organisms at the Permian–Triassic boundary in the Boreal Superrealm is discussed. [ABSTRACT FROM AUTHOR]

Abstract The numerous discoveries of disintegrated skeletons of large terrestrial vertebrates within several thin levels of the Upper Silesian Keuper initiated broad investigations into the palaeoenvironment and age of the bone-bearing sediments. Despite years of research, the depositional history of the Upper Triassic continental succession and its controlling factors are still poorly recognized. This paper reconstructs the depositional evolution of the Upper Triassic strata in Upper Silesia, Poland, discusses the tectonic and climatic control on deposition, and identifies the sediment provenance. Detailed sedimentological analysis enabled the recognition of three major palaeoenvironments: (1) playa; (2) distal floodplain featured by gilgai micromorphology; (3) fluvial system (sand-dominated meandering, sand- and gravel-dominated braided, and potentially anastomosing river system). The transition from one palaeoenvironment into another reflects climatic changes throughout the late Triassic. The Carnian interval is dominated by gypsum-rich playa mudstones deposited under hot and arid conditions, with only one wet episode recorded as meandering river sandstones (the so-called Carnian Pluvial Event). In contrast, Norian sedimentation was controlled by strong seasonal climatic variations, which is reflected in alternating palaeosol horizons (vertisols and calcisols), thin claystone beds (small water-pond deposits), and conglomerates (rapid flood events). This facies assemblage was formed in a relatively stable floodplain which became the main habitat of numerous vertebrate organisms. The Rhaetian is represented by a gravel-dominated braided river system developed in response to significant climate humidification, with tectonic controls on flow direction. Clast types from Norian and Rhaetian conglomerates revealed that the studied area was fed from the south and south west by the San River and Moesian Massifs. Geochemical analysis of Norian palaeosol horizons suggests mean annual precipitation of ~720 mm/yr in agreement with the palaeoclimatic reconstructions for the area, pointing to seasonal sub-humid to semi-arid climate conditions. Highlights • Carnian-Norian terrestrial deposits from SE Germanic Basin represent playa and gilgai-type floodplain environments. • The evolution of gilgai environments was mainly controlled by climatic changes through Late Triassic. • Gravel analysis indicates San River and Moesian platform sources. • Palaeosol type and geochemistry indicate climatic seasonality with precipitation at 720 mm/yr. [ABSTRACT FROM AUTHOR]

Abstract Transmission Electron Microscopy Tomography (TEMT) stands as a novel and alternative tool to tridimensionally model the nano-scale pores of rocks. In this study it is flanked with traditional Mercury Capillary Injection Porosimetry (MICP), Nitrogen adsorption Porosimetry (NP) and Scanning Electron Microscopy (SEM) analysis, to test a sample belonging to an Upper Triassic dolostone cropping out in Northern Calabria. MICP revealed low values of porosity and permeability, 2.3% and the 0.11 mD respectively. Nanopores account for the 94% of the pore volume, whereas the remaining 6% is represented by micropores. The integrated MICP and NP pore size distribution (PSD) shows the presence of a dominant pore diameter population coincident with 50 nm, with minor peaks at diameters of 12 μm, 850, 25, 13, 6, 2 nm. However, since the PSD peaks of the two techniques do not match, a comparison of the two curves is necessary to better characterized the overlapping area. SEM imaging analysis showed the presence of nano-scale intercrystalline and intracrystalline pores. The first corresponds with the spaces among dolomite crystals and, as suggested by the NP analysis, shows a wedge/slit morphology. The second appears with a prevailing polygonal section or as tight microfractures. Since SEM provides exclusively two-dimensional images, the morphology and development of these pores was obtained through TEMT 3D reconstruction. The 3D model showed the presence of open cavities, fractures and blind/isolated pores. Cavities cross the entire dolomite crystals and can present a constant (sub-prismatic pores) or variable channel section (funnel-shaped pores) that can reduce its aperture, as observed, of also more than a ten factor (e.g. from 300 nm to 20 nm). Fractures, commonly developing on the existing cleavage surfaces, cut the crystal faces for 300–350 nm, reducing its aperture (maximum of 20–30 nm) from the edge towards the inner part of the crystal. Lastly, blind/isolated pores can assume diameters and thickness of 250 nm. They show a sub-cubic morphology and, can be filled by solid, liquid or gaseous inclusions. Highlights • A dolostone pore system was investigated with a multi-technical approach. • The micro to nanopores distribution was obtained integrating Hg and N 2 porosimetry. • Nanopores Transmission Electron Microscope Tomography was tested for the first time. • 3D tomographic models show slit, cylindrical and pyramidal morphology of nanopores. • Closed pores potentially filled with solid, fluid or gas inclusions are also detectable. [ABSTRACT FROM AUTHOR]

Abstract In order to better predict the petrophysical properties of the tight sandstone reservoirs in the Upper Triassic Yanchang Formation, Ordos Basin, China, the nature of the diagenetic system involved was investigated using a suite of petrographic and geochemical techniques including thin section and X-Ray Diffraction analysis, scanning electron microscopy, MAPS mineralogy, Cathodeluminescence, electron probe microanalysis and fluid inclusion analysis on a set of selected tight sandstone samples. The sandstones investigated are texturally mature but compositionally immature with an average framework grain composition of Q 32 F 41 L 27. Authigenic quartz, calcite, and chlorite coatings are the major cements, while feldspars are partially dissolved. Two groups of quartz cement are present in the tight sandstone reservoirs. Smectite to illite conversion provided silica source for the first group of quartz overgrowth (Qo-I), while the silica source for the second quartz overgrowth (Qo-II) was mainly originated from feldspar dissolution. Calcite cements consist of two types, namely Ca-I and Ca-II. The Ca-I calcite cement contains no chlorite coatings and have higher concentrations of Fe2+ and Mg2+, whereas the Ca-II calcite cement developed over the chlorite coatings. Plagioclase dissolution appears to be always accompanied by calcite cementation, while K-feldspar albitization forms euhedral albite locally. The burial diagenesis processes were, in most cases, not episodic but occurred as slow adjustments in response to increased burial depths and temperatures. In all the studied diagenetic minerals, elemental distributions appear to be strictly constrained by the interaction of authigenic minerals involved, indicating that the chemical reactions during the diagenesis comply well with the general principle of mass balance. The diagenesis in the Upper Triassic Yanchang Formation tight sandstones was thus mainly developed in a closed geochemical system, where mineral dissolution and precipitation are approximately balanced, and diagenetic fluids were not affected by external sources significantly. Mechanical compaction has played a more important role in destroying the primary porosities of the Upper Triassic Yanchang Formation than the cementation. Highlights • There are two groups of quartz cement in the tight sandstone reservoirs. • Two types of calcite cement are present in the tight sandstone reservoirs. • Diagenesis of the tight sandstone reservoirs occurred in a closed geochemical system. [ABSTRACT FROM AUTHOR]

Abstract X-ray computed tomography (CT) is well known especially in medical applications, but more recently also in geosciences. In this study we present a model for characterizing the distribution and texture of pores and pore-throats in siliciclastic rocks using multi-scale 3D micro-CT imaging and apply this to reservoir rocks of the Edvard Grieg field comprising conglomerates and arenites. The conglomerates are highly heterogeneous and rich in clays which are carrying the majority of the porosity/microporosity. The sandstones display better sorting, permeabilities and porosities, in particular the aeolian samples, compared to the conglomerate matrix. The sandstones also have less clay and carbonate cement. In order to resolve porosity distribution below image resolution, the dry/wet method was applied. This method not only resolves porosity distribution below image resolution, but also the pore throats and connectivities. In this study we also investigate the effect carbonate cementation has had on the porosity and pore-throat characteristics. Low reservoir quality conglomerates (very tight conglomerates) are highly carbonate cemented which has reduced the pore-throat connectivity significantly. In the sandstone samples the pore filling carbonate cement is less abundant and has had a much smaller effect on the porosity reduction and pore throat geometries and, hence permeabilities. Highlights • Five different rock types have been analyzed. • "Dry/wet" micro-CT scans are used to resolve macro- and micropores. • Clay minerals and carbonate cement drastically reduce pore connectivity. • Clay rich conglomerate matrix carries a significant fraction of the microporosity. • Carbonate cement distribution is modeled and quantified. [ABSTRACT FROM AUTHOR]

Abstract Carbonate shoal reservoirs of the Middle Triassic Leikoupo Formation in the Sichuan Basin were investigated for potential gas resources. The carbonate shoal reservoirs can be divided on the basis of their formation mechanism into residual intergranular pore, karst (further divided into syndepositional-, burial-, and epigenetic-karstification types), dolomitized, and composite reservoirs. Residual intergranular pores and dissolved pores are the main reservoir spaces in the residual intergranular pore reservoirs. Isolated intragranular corroded pores and moldic pores are the main reservoir spaces in syndepositional-karstification reservoirs, the main spaces in burial-karstification reservoirs are dissolved pores and holes, and pores and caves on various scales are the main reservoir spaces of epigenetic-karstification reservoirs. Intercrystal pores and intercrystal solution pores are the main reservoir spaces of dolomitized reservoirs. Composite reservoirs are characterized by a variety of reservoir spaces with pores, holes, and fissures. High-quality shoal reservoirs were formed by superposition of carbonate shoals and constructive diagenetic modification. Preservation of residual intergranular pores was crucial for development of residual intergranular pore reservoirs. Platform-interior micro-highlands, relative declines in sea level, and rainfall controlled the development of syndepositional-karstification reservoirs. Dissolution by unsaturated acidic fluids, pre-existing pores and pore throats, and the direction of corrosive fluid flow were important for burial-karstification reservoirs. Epigenetic-karstification reservoirs formed as a result of significant sea-level drops or tectonic movement. Dolomitized reservoirs formed in shoals affected by dolomitization caused by evaporation of seawater or that occurred during burial. Composite shoal reservoirs were formed by two or more processes. Highlights • Carbonate shoal reservoirs developed in the Middle Triassic of the Sichuan basin. • Residual intergranular, karst, dolomitized, and composite pores were identified. • Preservation of residual intergranular pores was beneficial for high-quality reservoirs. • Minerals in shoals can be dissolved by syndepositional, burial, and epigenetic karstification. • Dolomitization with equal-volume metasomatism can enhance shoal reservoir ability. [ABSTRACT FROM AUTHOR]

Abstract—: The Middle-Late Permian reefs were formed in two paleogeographic realms: North Pangaea and Tethyan Realm. The basic reef builders in the first realm were representatives of Calcispongiae and Bryozoa; in the second realm, sphinctozoans, corals, and stromatoporoids. In these realms, various algae and cyanobacteria communities were of importance. Reef construction in the first realm associated with arid climatic conditions, isolation of water basins, and accumulation of salt-bearing sequences came to the end in the early Late Permian. Reef construction in the Tethyan Realm occurred in the Late Permian up to the Permian-Triassic boundary. The termination of reef construction was due to features of the reef ecosystem, which turned out to be unstable against the background of variations in the conditions and mass extinction at the Permian-Triassic boundary and dissociated before the termination of this extinction. [ABSTRACT FROM AUTHOR]

Abstract Sedimentary compression can produce deep changes in the organismal morphology during fossil diagenesis, so that intrinsic biological aspects (e.g. internal architecture of bones) could also generate non-natural traits when determinate bone element suffers sedimentary compression. Here we report a particular taphonomic case, in which the mode of preservation of a basal sauropodomorph from the Late Triassic of Brazil offers a valuable opportunity to examine the effects of sedimentary compression on a specific doubled body part of a single individual. The specimen is associated with two other almost complete and articulated individuals, comprising a monotypic association. The specimen herein studied presents the left ilium and hindlimb disarticulated from its body, where the right ilium was preserved with its ventral surface ventrally directed, and, conversely, the lateral surface of the left one was ventrally directed. Thus, their distinct placement in the substrate resulted in two distinct taphonomic histories reflected in their dissimilar shapes. This corresponds to a particular case of taphomorphic differences expressed in a single individual. Indeed, some of the peculiar traits of each ilium also occur in other specimens of close related taxa that experienced similar taphonomic histories. Sedimentary compression may produce dissimilar shapes in different portions of the skeleton, and incorrect observations generate what we call "taphoanatomical features", traits shared among close phylogenetic taxa/specimens resulting from similar taphonomic processes in response to specific biological aspects of the skeleton, not necessarily expressing phylogeny. Failing to recognize these trends could affect anatomical interpretations, especially regarding their role in a phylogenetic context. Highlights • We present a peculiar case of taphomorphy in a single specimen of sauropodomorph. • Both ilia present dissimilar shape in response of distinct placement on the substrate. • Sedimentary compression is pointed as responsible by its disparity. • The specimen is used to investigates the effects of compression in other specimens. • Thus, several traits resulted by similar taphonomic histories are suggested. [ABSTRACT FROM AUTHOR]

Potassium‐rich brine in the Sichuan Basin has been much studied in recent years, but few studies have focused on the distribution and migration of salt basin and the differences of potassium formation mechanisms. This work examined the salt‐gathering and potassium formation of potassium‐rich brine during the Triassic in the Sichuan Basin using lithofacies palaeogeographic depiction and geochemical analyses. (1) The favorable sedimentary facies controlling the formation of potassium‐rich brine during the Triassic in the Sichuan Basin are evaporation platform and restricted platform, whereas the salt basin is one of the main factors controlling the poly‐salt center. (2) The distribution and migration of this salt basin were affected by certain factors. The salt basin of the Jialingjiang Formation was mainly distributed in the east and central Sichuan Basin, whereas that of the Leikoupo Formation was mainly distributed in the central and west Sichuan Basin. The sedimentary centers have gradually moved westward and become smaller. (3) Three main formation mechanisms were identified for the potassium‐rich brine during the Triassic in the Sichuan Basin, i.e., evaporation and concentration of seawater, surface fresh water leaching, and deep water‐rock reaction. Fresh water leaching was characterized by low anomaly δ18O and δ13C values. Water‐rock reaction was mainly related to temperature, and high temperature environment (caused by burial depth, overthrust and deep hydrothermal fluids) was beneficial to water‐rock reaction. The characteristics of water‐rock reaction do not correspond to the increase ratio of K•103/Cl and Br•103/Cl in brine, and the Rb+ content of the brine was high. (4) The formation mechanisms of potassium‐rich brine differed between different areas of the Sichuan Basin. In east Sichuan, the evaporation and concentration of seawater, together with meteoric fresh water leaching, was the main formation factor, whereas the evaporation and concentration of seawater and water–rock reaction predominated in west Sichuan. This study of the sedimentary environment and formation mechanisms is of significance to the exploration and exploitation of potassium‐rich brine in the Sichuan Basin. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The Ondor Sum Group has different detrital age populations. • The Xilingol Complex was metamorphosed in Carboniferous (337–321 Ma) under HT-LP condition. • The low-grade metamorphic series along the Solonker suture zone has a metamorphic age of ∼240 Ma. • Four phases of metamorphism are identified in the metamorphic terranes in central Inner Mongolia. Abstract The tectonic evolution of the Xing'an-Inner Mongolia Orogenic Belt (XIMOB) in the southeastern segment of the Central Asian Orogenic Belt is not well understood. It is arguable whether the Paleo-Asian Ocean was closed in Devonian or Early Mesozoic and whether the tectonic regimes during Carboniferous and Permian were operated by continuous subduction-arc systems or extension after the orogenic process. Comprehensive studies of metamorphism for four metamorphic terranes including the Ondor Sum Group, Baoyintu Group, Xilingol Complex, and early Triassic metamorphic sequences in central Inner Mongolia provide good constraints on the arguable issues about the XIMOB. According to the zircon U-Pb dating analyses in this study, quartz schists of the Ondor Sum Group in the northern and southern orogenic belts (NOB and SOB) have a broad detrital zircon age range from late Archean to early Paleozoic with a similar youngest deposition age of 434–430 Ma, but have different zircon age populations with a ∼650 Ma peak for the NOB but not for the SOB. Biotite gneisses of the Xilingol Complex have age populations and the youngest deposition age of 436 Ma similar to the Ondor Sum Group in the NOB. Amphibolites in the complex have a metamorphic zircon age of 321 ± 3 Ma and hornblende 40Ar/39Ar age of 309 ± 2 Ma. The early Triassic metamorphic sequences, metabasites in Wulangou and mica-schists in Shuangjing both have broad zircon age ranges from the late Archean to late Paleozoic. Their protoliths are constrained to have formed later than 258 Ma and 261 Ma respectively and the metamorphism occurred soon afterwards in the Early Triassic constrained by an actinolite 40Ar-39Ar age of 241 ± 19 Ma in metabasite and a muscovite 40Ar-39Ar age of 240 ± 2 Ma in mica-schist. Combined with the results previously published, this study identified four phases of metamorphism in central Inner Mongolia since Paleozoic. The Silurian (430–426 Ma) high P/T metamorphism of the Ondor Sum Group was related to bidirectional subduction processes. The Devonian (∼400 Ma) medium P/T metamorphism of the Baoyintu Group suggests a crustal thickening orogeny. The Carboniferous (337–321 Ma) low P/T metamorphism of the Xilingol Complex is indicative of an extension process of a previous orogen. The Early Triassic (∼240 Ma) extensive medium-low P/T metamorphism along the Solonker suture zone was attributed to the closure of limited ocean basins. Thus, an alternative tectonic scenario for the metamorphic terranes in central Inner Mongolia involves: (i) the early Paleozoic trench–arc system (500–425 Ma); (ii) the Devonian collisional orogeny due to closure of the Paleo-Asian-Ocean (400–360 Ma); (iii) the Carboniferous and Permian extension after the collision (350–250 Ma), and (iv) the Early Triassic within-plate orogeny due to the closure of limited ocean basins (∼240 Ma). [ABSTRACT FROM AUTHOR]

The Early Mesozoic granitoids in the east-central Tibet are the key to understand the tectonic evolution of the Tibetan Plateau. In this study, three stages of Early Mesozoic granitic magmatism were indicated by LA-ICP-MS zircon U-Pb dating on 14 samples. The Early Triassic (248-243 Ma) and the Late Triassic (213-208 Ma) were distributed in the North Qiangtang terrane, and the Early Jurassic (ca. 187 Ma) occurred in the Tongka and Jiayuqiao blocks. The Late Triassic and Early Jurassic granitoids show similar negative zircon εHf(t) values (− 5.5 to − 16.6) with TDM2 model ages of 1.60-2.28 Ga, suggesting a Paleoproterozoic crustal source, whereas the Early Triassic granitoids have zircon εHf(t) values from − 3.4 to + 5.3 with TDM2 model ages of 0.94-1.50 Ga, indicating a Mesoproterozoic crustal source. Based on the whole-rock geochemical data, we suggest that the Early Triassic rocks from the North Qiangtang terrane include I- and S-type granites and the Late Triassic rocks are S-type granites, which were related to the northward subduction of the Longmu Tso-Shuanghu-Dingqing Paleo-Tethys Ocean and subsequent collision between the North Qiangtang terrane and Tongka block, respectively. The Early Jurassic granitoids from the Tongka and Jiayuqiao blocks also included both I- and S-type granites and were probably generated in an arc-related setting during the northward subduction of the Bangong-Nujiang Tethys Ocean. Therefore, we suggest a collision-accretion model that attributes the Early Mesozoic tectonic-magmatic event to the sequential multistage subduction and collision in the east of central Tibet. [ABSTRACT FROM AUTHOR]

Both sedimentology and sequence stratigraphy variability in the deltaic area are distinguished in the fan‐delta system of the Northwestern Junggar Basin. Sediment supply plays a significant role in controlling the fan‐delta petrology, evolution, and depositional processes and the delivery of sediment into deeper parts of the basin. The results of this study show that variations in the lithology of the sediment supply control the fan‐delta petrology and spatial and temporal variations in sediment supply influence the location and shifting of depocentres. A fining‐upward fan‐delta succession developed as accommodation rates outpaced the sediment supply rate. Frequent flood events were mostly recorded by sediment gravity flow deposits, which in turn influenced the geometry of the sandstone bodies and their reservoir quality. Hyperpycnal flow was a significant delta front process and an important mechanism for sediment delivery into deeper waters, favoured by the combination of denudation of coastal ranges and the fresh waters of the receiving basin. This study highlights that a detailed understanding of variations in sediment supply is essential to accurately predict sediment partitions in a delta system and the delivery of coarse‐grained sediments into deeper parts of lacustrine basins. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The mineral component difference between the lamina and surrounding rock are the more important. • Middle lamina angles are suitable for LF propagation. • Sheet sandstone and turbidite sandstone are the good for LF propagation. • All the LF observed in thin sections are associated with oil, and tested with C and O isotope data. Abstract Lamina induced fractures (LF) are abundant in lacustrine formations, playing an important role for the tight oil resource exploration. Studies of controlling factors of the LF are still lacking, especially for the heterogeneous formations characterized with complex combinations of the lamina and surrounding rock. Therefore, 28 long column samples for triaxial compression tests, 37 short column samples for Brazil split tests and 12 powder samples for mineral component analysis and isotopes analysis (carbon and oxygen) are made from 6 cores in 4 petrophysical faces. The experiments are designed to study the LF propagation process, considering the controlling factors in terms of mineral component, the lamina angle and the petrophysical faces. Our results show that: Clay content and dolomite cement degree more significantly control the LF propagation than the other minerals; The LF propagation is not only dependent on the mineral component in the lamina, but even more on the mineral component difference between the lamina and the surrounding rock (i.e., the L/S values), where ‘L’ represents the lamina and ‘S’ represents the surrounding rock adjacent to the lamina; The LF tended to propagate in a middle lamina angle range (approximately 10°–60°) in shear properties, and characterized with lower compression strength values; All the LF observed in the thin sections were associated with oil, although there was no obvious oil shown in the study cores; The δ13C and δ18O values of lamina samples varied with the lamina mineral component for the complex organic matter oxidation and degradation reactions. Additionally, the hydrocarbon flow parameter (P HF) has been proposed on the carbon and oxidation isotope trace lines, to indicate the oil-rock reactions during the LF open period. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The Kon Tum massif is an Early to Middle Triassic Metamorphic Core Complex (MCC). • A top-to-the NW ductile shearing accommodated the exhumation. • The MCC superimposes on an Early Paleozoic collision belt between N. and S. Vietnam. • The collision was the driver of the Early Paleozoic intracontinental belt of S. China. • The interaction between Emeishan mantle plume and continental subduction is proposed. Abstract In Central Vietnam, the Kontum massif is subdivided from North to South into: (i) Kham Duc, (ii) Ngoc Linh, (iii) Kan Nack complexes. The Kham Duc complex consists of metapelite, metapsammite, paragneiss, metagabbro, amphibolite, serpentinized ultramafic, and orthogneiss blocks. The southern part of this complex experienced an Early Paleozoic crustal melting event responsible for migmatites and anatectic granites. The Ngoc Linh complex, the largest one, is formed by metatexite and granitoid enclosing blocks of eclogite, high pressure (HP) granulite, orthogneiss, metagabbro, amphibolite, granodiorite, and migmatite. The Kan Nack complex is formed by migmatites with (ultra) high temperature (U)HT granulite, charnockites and enderbites. The three metamorphic complexes are intruded by per-aluminous granite, and subordinate mafic plutons. In spite of local variations, the foliation of the Ngoc Linh complex defines a bulk domal structure, and the stretching lineation consistently trends NW-SE. The NW-SE lineation is also observed in the tectonically overlying the Kan Nack complex. The Ngoc Linh and Kan Nack complexes are interpreted here as parts of a metamorphic core complex (MCC), or “Ngoc Linh MCC”, exhumed by a top-to-the-NW detachment fault. Along the northern margin of the Ngoc Linh MCC, upright folds with E-W striking axes, and E-W stretching lineation deform the foliation. These structures are developed in a transpressive regime coeval with the activity of plurikilometer-scale dextral strike-slip faults. Zircon and monazite U/Pb radiometric datings document a 250–240 Ma age for the crustal melting, and the top-to-the-NW ductile shearing coeval with the formation of the Ngoc Linh MCC. This extensional tectonics is followed by a dextral strike-slip faulting, at ca 240–230 Ma, before the emplacement of the two-mica granitic plutons at ca 240–224 Ma. Furthermore in the Ngoc Linh and Kan Nack complexes, zircon and monazite yield U-Pb Early Paleozoic ages. In the Kham Duc complex, a ca 460 Ma MP/MT, garnet-biotite-staurolite-kyanite metamorphism, followed by migmatites at ca 450 Ma, is also recognized. The 420–400 Ma age of the Dai Loc plutonic suite, and the 450–425 Ma age of the Dien Binh calc-alkaline granodiorite document an Early Paleozoic event. The Early Paleozoic mafic and ultramafic masses of the Hiep Duc complex are ophiolites included into a metasedimentary matrix. Thus, the Kham Duc complex is interpreted as a tectonic mélange formed during a collisional orogeny that subsequently underwent crustal melting giving rise to the migmatites. A part of the Early Paleozoic rocks are enclosed as xenoliths in the Triassic migmatite of the Ngoc Linh MCC. These petrologic, structural, and chronological features allow us to propose the following geodynamic evolution for the Kontum massif. During the Early Paleozoic, a continental collision, which was accommodated by a north-directed subduction of a southern block (S. Vietnam, or Viet-Cambodia block) below a northern block (N. Vietnam or Viet-Lao block), occurred along the Tam Ky-Phuoc Son suture. During the Early Triassic, at ca 250–245 Ma, the S. Vietnam block experienced a crustal melting giving rise to the Ngoc Linh MCC that reworked the Early Paleozoic orogen. Lastly, during the Middle Triassic, the dextral faulting superimposed upon the Ngoc Linh migmatite. The geodynamic significance of the Kontum massif is discussed in the general framework of Indochina- South China relationships. The Early Paleozoic collision in Vietnam is viewed as the driving force responsible for the development of the intracontinental orogeny of S. China. In order to account for the important heat flow required for the formation of UHT metamorphic rocks, a possible interaction between the SCB-Indochina collision, and the Emeishan mantle plume is proposed. [ABSTRACT FROM AUTHOR]

N and C isotopic data are recorded and presented for the first time for the Lower Triassic claystones of Southern Primorye (Abrek Section). Five N isotope intervals and 11 more or less pronounced negative C isotope excursions, likely to reflect instability of the temperature regime and the oceanographic situation in the Early Triassic, are recognized in the section. The most favorable conditions for ammonoid recovery and other marine organisms in the Early Triassic (after the end- Permian ecological crisis) were associated with the late Induan—early Olenekian transgression and probable cooling. [ABSTRACT FROM AUTHOR]

The distribution pattern of oil and gas in the western part of central Sichuan Basin is complicated, there are many different views on the sources of natural gas, which restrict further exploration and deployment of oilfields. Therefore, by analyzing geochemical characteristics and quantitative calculation of natural gas in study area, combined with the data of structure and gas-oil ratio, the origin and sources of gas are discussed and analyzed. The results show that the dryness coefficient of the natural gas ranges between 0.71 ∼ 0.93, δ 13 C values range between −45.3 ∼ −38.0‰ in methane, −32.0 ∼ −25.6‰ in ethane and −30.0 ∼ −25.3‰ in propane. Crossplots of isotope data and quantitative calculation indicate that natural gas in Da'anzhai Member is characterized by the mixture of sapropelic and humic natural gas, the humic gas largely occupies the proportion of 20–40%, up to 70%. It is the result of upward migration of natural gas in Triassic Xujiahe Formation. The abnormally high gas-oil ratio is an important manifestation of this upward intrusion. Based on the study of high gas-oil ratio wells, the distribution of humic natural gas that intruded from Xujiahe Formation and enriched in Da'anzhai Member is unevenly distributed. It inherits characteristics of “Plaque accumulation” of natural gas in Xujiahe Formation. The inhomogeneity of this plane distribution is controlled by fault location, fault scale and the size of underlying Xujiahe Formation gas reservoirs. The humic gas from Xujiahe Formation occupies a large proportion in blocks of Da'anzhai Member which are favorable for intrusion, accumulation and preservation of Xujiahe Formation natural gas, whereas for blocks without these conditions, natural gas is often associated gas. [ABSTRACT FROM AUTHOR]

Abstract: The Marrakech High Atlas contains some of the best exposures of the Triassic early‐rift strata related to Atlantic opening in NW Africa. We present the first detrital zircon U–Pb data of five Triassic redbed samples from the Tizi n'Test basin to quantify sediment provenance, transport and dispersal patterns during early rifting. These U–Pb ages document dominant sediment sourcing from the south, the Anti‐Atlas domain, with very limited to absent input from the Variscan Meseta domain to the north. This combined with stratigraphic and thermochronologic information points to a highly asymmetric palaeogeography during Triassic rifting. Furthermore, the occurrence of Archaean detrital zircon grains in Triassic sandstone, likely recycled from the Reguibat shield, suggests the presence of a fully developed regional drainage system with rivers and catchments reaching hundreds of kilometres into the hinterland of the rift flank. [ABSTRACT FROM AUTHOR]

Detrital chrome spinel (Cr-spinel) is for the first time described from the Nakhlak Group, which is a distinctive Triassic (Late Olenekian‒?Early Carnian) sedimentary succession in Central Iran. Previously published data from the Nakhlak Group suggest deposition along an active margin during the Triassic and Eurasian affinity. Presently, the Nakhlak Group is located in the northwestern region of the Central-East Iranian Microcontinent, a major segment of the Cimmerian block. The Nakhlak region is believed to have been dislocated from its prior position at the Turan Plate from the southern Eurasian active margin after deposition in Triassic time. Almost all of the analyzed detrital Cr-spinels have high Cr-numbers (0.6–0.85), variable Mg-numbers (0.33–0.78), and low Fe 3+ (<0.25), Al 2 O 3 (<20 wt%) and TiO 2 (<0.4 wt%) contents, suggesting a magmatic source for the Cr-spinels formed both within oceanic (mainly harzburgitic) mantle and in a supra-subduction zone (SSZ) tectonic setting. The data suggest that mafic‒ultramafic rock assemblages with SSZ signatures were generated in the Paleo-Tethyan realm before their obduction as an ophiolite. By comparing data from the present study with results from previous work on the Triassic in Central Iran it is evident that Paleo-Tethyan ophiolites of intra-oceanic island-arc (IOIA) origin supplied detrital material to the Nakhlak Group at the southern margin of Eurasia during pre-to syn-Eocimmerian tectonics in the Triassic. [ABSTRACT FROM AUTHOR]

The Indosinian orogeny experienced multiple subduction-collisional events along the Jinshajiang-Ailaoshan-Song Ma tectonic zone in response to closure of the Paleotethyan Ocean/back-arc basin, but the associated geodynamic processes are still poorly understood. Granitic rocks are the most common magmatic products in collisional orogens, and they can provide important information about orogenic geodynamics. In this study, three stages of collision-related igneous activity were identified along the Jinshajiang-Ailaoshan-Song Ma suture zone: (1) Latest Permian to earliest Triassic (ca. 255-248 Ma) high-εHf(t) and high-εNd(t) I-type granites, low-εNd(t) and low-εHf(t) I-type granites, and S-type granites; (2) Early to Middle Triassic (247-237 Ma) S-type leucogranites and high-Si peraluminous rhyolites; and (3) Late Triassic (ca. 235-202 Ma) high-εNd(t) and high-εHf(t) I-type granites, low-εNd(t) and low-εHf(t) I-type granodiorites, and S-type granites. A synthesis of the data for the latest Permian to Triassic magmatic and coeval high-pressure and ultrahigh-pressure metamorphic rocks suggests a three-stage model for the convergence between the Simao-Indochina and South China blocks. Termination of arc magmatism and commencement of continental collision occurred in the latest Permian-earliest Triassic (ca. 255-248 Ma), followed by continental subduction in the Early to Middle Triassic (247-237 Ma) and Late Triassic postcollisional slab breakoff and continental exhumation (ca. 235-202 Ma). A two-dimensional high-resolution numerical model reproduced this evolutionary process and revealed the lateral structural heterogeneity of the subducting and overriding plates during the Indosinian orogeny. [ABSTRACT FROM AUTHOR]

The Triassic stratigraphic framework for the Song Da and the Sam Nua basins, north Vietnam, suffers important discrepancies regarding both the depositional environments and ages of the main formations they contain. Using sedimentological analyses and dating (foraminifer biostratigraphy and U-Pb dating on detrital zircon), we provide an improved stratigraphic framework for both basins. A striking feature in the Song Da Basin, located on the southern margin of the South China Block, is the diachronous deposition, over a basal unconformity, of terrestrial and marine deposits. The sedimentary succession of the Song Da Basin points to a foreland setting during the late Early to the Middle Triassic, which contrasts with the commonly interpreted rift setting. On the northern margin of the Indochina Block, the Sam Nua basin recorded the activity of a proximal magmatic arc during the late Permian up to the Anisian. This arc resulted from the subduction of a southward dipping oceanic slab that separated the South China block from the Indochina block. During the Middle to the Late Triassic, the Song Da and Sam Nua basins underwent erosion that led to the formation of a major unconformity, resulting from the erosion of the Middle Triassic Indosinian mountain belt, built after an ongoing continental collision between the South China and the Indochina blocks. Later, during the Late Triassic, as syn- to post-orogenic foreland basins in a terrestrial setting, the Song Da and Sam Nua basins experienced the deposition of very coarse detrital material representing products of the mountain belt erosion. [ABSTRACT FROM AUTHOR]

The Culzean Field, located in UK CNS Block 22/25a between the Lomond Deep and the Heron Cluster, was discovered in 2008 by the 22/25a-9Z well and subsequently appraised by wells 22/25a-10, 22/25a-10Z, 22/25a-10Y and 22/25a-11. The primary reservoir is the Triassic Skagerrak Formation, with a secondary reservoir in the Middle Jurassic Pentland Formation. Total recoverable reserves are estimated to be 250 - 300 MMBOE. One principal challenge concerning the Skagerrak reservoir in Culzean is the stratigraphy, and especially how it relates to adjacent wells in Quadrant 22. Historically, biostratigraphic age determinations of the Skagerrak Formation in Quadrant 22 have been unsuccessful, unlike in Quadrant 30 where biostratigraphic recovery is good and ages are well established. However, good recovery in the Culzean discovery well 22/25a-9Z enabled identification of the Jonathan Mudstone Member, the Joanne Sandstone Member, the Julius Mudstone Member, the Judy Sandstone Member and Marnock Mudstone. The Joanne Sandstone Member and the Jonathan Mudstone Member are therefore more widely distributed in Quadrant 22 than has been hitherto recognized. The Skagerrak Formation in Culzean also has a well-defined heavy mineral stratigraphy, enabling correlation into the adjacent Marnock, Skua, Egret and Heron fields. This correlation shows that the reservoir succession in Egret and Heron is largely equivalent to the Joanne Sandstone Member, whereas Marnock and Skua contain the Judy Sandstone Member overlain by truncated Joanne Sandstone Member and Julius Mudstone Member intervals. [ABSTRACT FROM AUTHOR]

Jaw elements of Omphalosaurus sp. are described from the Early Triassic (Spathian) of Marmierfjellet, Spitsbergen. The elements are from the Grippia and the Lower Saurian niveaus in the Vendomdalen Member of the Vikinghøgda Formation. In the Grippia niveau a bonebed was excavated in 2014-15 and a large number of ichthyopterygian elements were recovered. Together with the omphalosaurian jaw elements a collection of large vertebral centra were recognized as different from the smaller Grippia centra and more than 200 large vertebral centra are referred to Ichthyopterygia indet. and tentatively assigned to regions of the vertebral column. We refrain from further assignment due to the systematic position and the difficulty of defining criteria for recognizing postcranial elements of Omphalosaurus. [ABSTRACT FROM AUTHOR]

This study analyzes in detail the beds bearing Rhizocorallium in the Upper Triassic Nayband Formation (Tabas Block, Central Iran) and shows their potential in interpreting depositional settings, ecological features and sequence stratigraphy. An integrated approach combining ichnological, sedimentological and stratigraphic methods has significantly enhanced our understanding of the changes in the spatial distribution style and morphological differences among the same ichnospecies of Rhizocorallium . The Upper Triassic Rhizocorallium assemblages from the Nayband Formation reveal significant spatial variations in the orientation and dimensions (i.e., length, width, limb diameter), the tiering pattern, and the colonization style throughout systems tracts and at erosional discontinuities or omission surfaces. Based on the wide variety of forms and orientation, numerous morphotypes of Rhizocorallium are grouped into two main types, i.e., those that are mostly facies controlled and those that appear abundantly in a confined stratigraphic interval and are facies independent. In this respect, three paleoichnocoenoses or habitats for the rhizocorallid producers could be differentiated according to the burrow morphology and the nature and consistency of the substrate: (1) stable habitat, represented by soft substrates including horizontal, long, straight or slightly sinuous, spreite-bearing, U-shaped protrusive burrows of Rhizocorallium irregulare (= R. commune var. irregulare ). This habitat resulted from processes operating in settings that are characterized by soft substrates, reduced sedimentation rates, and abundant food supply, typical of low- to moderate-energy, fully marine conditions; (2) unstable, physically-controlled habitat, represented by a suite of shifting substrates with low- to high-energy settings, including short, U-shaped protrusive spreiten-burrows of R. jenense (Type 1) . In this habitat alternating and contrasting energy conditions did exist due to repeated storm events that were the main controlling factor in the distribution and preservation of Rhizocorallium ; (3) substrate-controlled habitat represented by a suite of stiff-to-firm substrates including oblique to vertical protrusive or retrusive spreiten U-shaped burrows of R. jenense (Type 2) . The erosional discontinuities or omission surfaces related to this habitat include parasequence-bounding transgressive surfaces of erosion (TSE) and parasequence-bounding flooding surfaces (FS) and are mainly associated with the Rhizocorallium -dominated Glossifungites ichnofacies. Complementary ichnological information indicates that the shift in the orientation and the morphological features of rhizocorallid burrows point to broad changes of environmental parameters, which are, in turn, controlled by the rate of sea-level changes. [ABSTRACT FROM AUTHOR]

Granites derived from partial melting of sedimentary rocks are generally characterized by high δ 18 O values and abundant relict zircons. Such relict zircons are valuable in tracing the source rocks of granites and the history of crustal anatexis. Here we report in-situ U-Pb ages, O isotopes and trace elements in zircons from Triassic granites in the Zhuguangshan and Jiuzhou regions, which are located in the Nanling Range and the Darongshan area, respectively, in South China. Zircon U-Pb dating yields magma crystallization ages of 236 ± 2 Ma for the Zhuguangshan granites and 246 ± 2 Ma to 252 ± 3 Ma for the Jiuzhou granites. The Triassic syn -magmatic zircons are characterized by high δ 18 O values of 10.1–11.9‰ in Zhuguangshan and 8.5–13.5‰ in Jiuzhou. The relict zircons show a wide range of U-Pb ages from 315 to 2185 Ma in Zhuguangshan and from 304 to 3121 Ma in Jiuzhou. Nevertheless, a dominant age peak of 700–1000 Ma is prominent in both occurrences, demonstrating that their source rocks were dominated by detrital sediments weathered from Neoproterozoic magmatic rocks. Taking previous results for regional granites together, Neoproterozoic relict zircons show δ 18 O values in a small range from 5 to 8‰ for the Nanling granites but a large range from 5 to 11‰ for the Darongshan granites. In addition, relict zircons of Paleozoic U-Pb age occur in the two granitic plutons. They exhibit consistently high δ 18 O values similar to the Triassic syn -magmatic zircons in the host granites. These Paleozoic relict zircons are interpreted as the peritectic product during transient melting of the metasedimentary rocks in response to the intracontinental orogenesis in South China. Therefore, the relict zircons of Neoproterozoic age are directly inherited from the source rocks of S-type granites, and those of Paleozoic age record the transient melting of metasedimentary rocks before intensive melting for granitic magmatism in the Triassic. [ABSTRACT FROM AUTHOR]

The Eastern Mediterranean region within the Tethyan belt is characterised by two main pulses of suprasubduction-zone ophiolite formation during the Early–Middle Jurassic and Late Cretaceous. Despite vast exposures of the Permo-Triassic accretionary complexes, related suprasubduction-zone ophiolites and the timing of subduction initiation leading to the formation of Permo-Triassic accretionary complexes are unknown so far. Here we report on a ~ 40 km long and 0.3 to 1.8 km wide metaophiolite fragment within transitional greenschist- to blueschist-facies oceanic rocks from NW Turkey. The metaophiolite fragment is made up mainly of serpentinite and minor dykes or stocks of strongly sheared metagabbro with mineral assemblages involving actinolite/winchite, chlorite, epidote, albite, titanite and phengite. The metagabbro displays (i) variable CaO and MgO contents, (ii) anomalously high Mg# (= 100 ∗ molar MgO/(MgO + FeO tot )) of 75–88, and (iii) positive Eu anomalies, together with low contents of incompatible elements such as Ti, P and Zr, suggesting derivation from former plagioclase cumulates. The serpentinites comprise serpentine, ± chlorite, ± talc, ± calcite and relict Cr-Al spinel surrounded by ferrichromite to magnetite. Relict Cr-Al spinels are characterised by (i) Cr/(Cr + Al) ratios of 0.45–0.56 and Mg/(Mg + Fe 2 + ) ratio of 0.76–0.22, (ii) variable contents of ZnO and MnO, and (iii) extremely low TiO 2 contents. Zn and Mn contents are probably introduced into Cr-Al spinels during greenschist- to blueschist metamorphism. Compositional features of the serpentinite such as (i) Ca- and Al-depleted bulk compositions, (ii) concave U-shaped, chondrite-normalised rare earth element patterns (REE) with enrichment of light and heavy REEs, imply that serpentinites were probably derived from depleted peridotites which were refertilised by light rare earth element enriched melts in a suprasubduction-zone mantle wedge. U-Pb dating on igneous zircons from three metagabbro samples indicates igneous crystallisation at 262 Ma (middle Permian). Timing of the metamorphism is constrained by incremental 40 Ar/ 39 Ar dating on phengitic white mica at 201 Ma (latest Triassic). We conclude that the metaophiolite represents a fragment of middle Permian suprasubduction-zone oceanic lithosphere, involved in a latest Triassic subduction zone. These data, together with several reports in literature, indicate that the middle Permian was a time of suprasubduction-zone ophiolite formation in the Tethyan belt. [ABSTRACT FROM AUTHOR]

An integrated petrologic, geochronologic, major and trace element geochemical, and Sr-Nd-Hf isotopic study of Late Triassic (~ 215 Ma) diorites from the Hoh Xil area, northern Tibet, provides new constraints on the genesis of intermediate magmas and insights into the origin of the high-Mg# andesitic signature of continental crust. These dioritic rocks are characterized by high MgO contents (3.3–5.0 wt%) and Mg# values (50–57) comparable to the estimates for the bulk continental crust at the same level of SiO 2 contents (61.1–64.5 wt%). They also display continental crust-like trace element distribution patterns and uniformly enriched isotope compositions ([ 87 Sr/ 86 Sr] i = 0.7081 to 0.7094, ɛNd[t] = − 8.0 to − 6.9, and ɛHf[t] zircon = − 10.1 to − 5.0). Combining our results with published data from crystallization experiments, we propose that they were probably produced by fractional crystallization from a primitive andesite parent, rather than a primitive basalt parent. This parental magma may be geochemically similar to the roughly contemporaneous primitive andesites in the adjacent Malanshan area of northern Tibet. Our compilation of modern arc lavas shows that progressive fractional crystallization of primitive andesites is also required to reproduce the Mg# versus SiO 2 array for natural arc magmas, in addition to differentiation of mantle-derived primitive basaltic magmas and/or mixing of basaltic with felsic magmas. Therefore, we emphasize that fractional crystallization of primitive andesitic magmas is potentially a frequent occurrence in arc crust and hence may play an important role in producing the high-Mg# signature of intermediate magmas comprising the continental crust. [ABSTRACT FROM AUTHOR]

The Bayan Har Orogen comprises a major part of the “Qingzang-Dianxi fold region” in western China. It preserves important information of the tectono-thermal evolution covering the time span from the closure of the Paleo-Tethys Ocean up to the formation of the Himalayas. Low temperature metamorphic indicators, such as mineral assemblages, illite “crystallinity” (IC), chlorite “crystallinity” (CC), illite polytype, b -cell dimension of K-white micas, geothermometry of selected minerals were analyzed. The values of Kübler index (KI) of the Triassic flysch in the Bayan Har Orogen range from 0.23–1.63°Δ2θ while Árkai index (ÁI) in a range of 0.21–0.60°Δ2θ. Iso-thermal zones mapped with KI describe a pair of anchizones and an anchiregion within the Bayan Har Orogen: the “Giant Yushu Anchizone” in the southwest (extending > 750 km long and 100 km wide), the “Zaling-Eling-Lakes Anchizone” in the center (about 150 km long and 40 km wide) and the “Xing-Tong-Zhe Anchiregion” in the northeast (covering an area of roughly 60,000 km 2 ). They are separated by diagenetic zones. Peak metamorphic conditions are estimated around 280–330 °C and a low to intermediate (N. New Hampshire) pressure type. A slight change with increasing then decreasing pressure was observed from SW to NE. The relationship between anchimetamorphic pattern of Triassic flysch and large-scale folds and faults indicates syn- to post structural metamorphism. Compression at the end of the Triassic, induced by the interaction of the Tarim, North China and Indian blocks caused the closure of the Paleo-Tethys Ocean and led to the folding of the Triassic flysch within the Paleo-Tethys Ocean basin. Anchimetamorphism may have been caused by crustal thickening of > 10 km due to an accretionary wedge setting and a temperature increase in those rocks due to burial. Such a regional metamorphic pattern would provide important information for reconstruction of palaeotectonic-palaeogeograph and the evolutionary history of Tibetan plateau. [ABSTRACT FROM AUTHOR]

The Triassic formation is a possible new giant hydrocarbon generated formation in Northwest China and Mid-Asia. Taking the Upper Triassic formation in the Sikeshu Sag in Junggar Basin as an example, based on the comprehensive analysis on the geochemical characteristics of the cores and the dark mudstone of the outcrops and reservoir formation conditions, we have evaluated the Upper Triassic source rocks by comparing with those in the Ulungu Depression, and reached the following findings. Firstly, the Upper Triassic formation is mainly composed of dark mudstone and sandy mudstone deposits, and the hydrocarbon source rock is mainly distributed in the middle and upper parts with a thickness range of 100–150 m and area of 3500 km 2 . Secondly, the source rock, moderate in organic matter abundance (with TOC range of 1%–3%), has the material basis for hydrocarbon generation. Thirdly, the organic matter has high percentage of sapropelinite, and is dominated by type II 2 . Fourthly, the degree of the thermal evolution is moderate, and the source rock with R o higher than 0.7% has a distribution area of about 1800 km 2 , providing the conditions of massive hydrocarbon generation. Fifthly, the source rock has great burial depth and wide distribution; the source rock with a R o of higher than 0.7% and thickness of more than 100 m has an area of around 1400 km 2 , implying huge resource potential. Sixthly, the next step exploration should focus on highly mature hydrocarbon generation central area in the Upper Triassic - Lower Jurassic in the east of the sag to search for and confirm favorable traps. The research findings have important reference value for promoting the resource status of, deepening the understanding of reservoir formation, and clarifying the exploration direction in the Sikeshu Sag and other periphery Mid-Asia areas. [ABSTRACT FROM AUTHOR]

The pore system of two dolomitized Triassic carbonate platforms, named Lower and Upper Unit and cropping out in Southern Italy, has been investigated through mercury porosimetry and electron microscopy. Despite their variability, all facies show micro-to nano-pores systems composed of intra- and inter-crystal pore types; this is due to the prevalence of microbialites in the inner platform-margin settings together with an homogenous diagenetic history. Porosity and permeability are generally very low (<3% and <1 mD in average respectively) and, as the median of pores diameter is < 1 μm and the median of the nanopores volume is >60%, the porosity derived from nanopores is significant in all facies, and particularly in the shallow-water environments. A positive correlation between nanopores volume and porosity is present in the whole Upper Unit and in the shallow-water facies of the Lower Unit. Moreover, different sub-environments of the platforms show separated amount of nanopores and porosity; on the contrary, permeability does not seem to be influenced by the nanopores distribution. Regardless a wide spectrum of fabric and morphologies, microbialitic facies of both units show a confined range of porosity (average: 1,0% standard deviation: 0,6) and permeability (average: 0,4% standard deviation: 0,2), most probably because composed of syn-sedimentary microbial dolomite, which presents a high resistance to compaction during the burial history. Finally, despite the complete dolomitization, porosity and permeability ratio varies in function of the main depositional environments, and less of the precursor sedimentary facies, suggesting a control of the final pore-size distribution mainly linked with the presence/absence of the microbial primary dolomitic facies instead of the native fabrics of the other sedimentary facies. [ABSTRACT FROM AUTHOR]

Geological records reveal a number of ancient, large and rapid negative excursions of the carbon-13 isotope. Such excursions can only be explained by massive injections of depleted carbon to the Earth system over a short duration. These injections may have forced strong global warming events, sometimes accompanied by mass extinctions such as the Triassic-Jurassic and end-Permian extinctions 201 and 252 million years ago, respectively. In many cases, evidence points to methane as the dominant form of injected carbon, whether as thermogenic methane formed by magma intrusions through overlying carbon-rich sediment or from warming-induced dissociation of methane hydrate, a solid compound of methane and water found in ocean sediments. As a consequence of the ubiquity and importance of methane in major Earth events, Earth system models for addressing such events should include a comprehensive treatment of methane cycling but such a treatment has often been lacking. Here we implement methane cycling in the Danish Center for Earth System Science (DCESS) model, a simplified but welltested Earth system model of intermediate complexity. We use a generic methane input function that allows variation in input type, size, timescale and ocean–atmosphere partition. To be able to treat such massive inputs more correctly, we extend the model to deal with ocean suboxic/anoxic conditions and with radiative forcing and methane lifetimes appropriate for high atmospheric methane concentrations. With this new model version, we carried out an extensive set of simulations for methane inputs of various sizes, timescales and ocean–atmosphere partitions to probe model behavior. We find that larger methane inputs over shorter timescales with more methane dissolving in the ocean lead to ever-increasing ocean anoxia with consequences for ocean life and global carbon cycling. Greater methane input directly to the atmosphere leads to more warming and, for example, greater carbon dioxide release from land soils. Analysis of synthetic sediment cores from the simulations provides guidelines for the interpretation of real sediment cores spanning the warming events. With this improved DCESS model version and paleo-reconstructions, we are now better armed to gauge the amounts, types, timescales and locations of methane injections driving specific, observed deep-time, global warming events. [ABSTRACT FROM AUTHOR]

The Middle to Upper Triassic series in the Norwegian Barents Sea represents an important target for hydrocarbon exploration. However, the dating and correlation of these rocks are problematic due to the scarcity of age-diagnostic macrofossils, lateral facies variation and the overall thickness of the succession. Palynology has proven to be a useful dating tool but further work is necessary to improve the zonal resolution, particularly for the Upper Triassic Series. The current paper presents a detailed palynostratigraphy of the Middle – Upper Triassic succession in four exploration wells (7120/12-2, 7228/2-1s, 7-1a and 9-1s) drilled in the Hammerfest and Nordkapp basins. Eleven informal palynological zones are described from the stratigraphic interval spanning the Kobbe, Snadd and Fruholmen formations, which constitute regionally significant hydrocarbon source and reservoir rock facies. The results of this study contribute to a higher resolution palynostratigraphy for the Middle to Upper Triassic strata of the southern Barents Sea (SBS), and an improved correlation with the stratigraphy of the Svalbard Archipelago. Palynofacies data for the succession, presented here for the first time, indicates depositional environments ranging from fluvio-deltaic to offshore marine. [ABSTRACT FROM AUTHOR]

The Triassic and Jurassic geology of northern Sonora encompasses important events that are linked to the late Paleozoic history of the region. The fossiliferous El Antimonio Group in the Sierra del Álamo includes the upper Permian-Triassic Antimonio, and Río Asunción formations and the Hettangian-Sinemurian Sierra de Santa Rosa Formation. These formations consist of upward-fining sequences from I to XIV that represent fluvial to shallow and deep marine environments of deposition. The Triassic/Jurassic boundary in this region is a hiatus represented by a disconformity between sequence IX of the Río Asunción formations and sequence X of the Sierra de Santa Rosa Formation. The shallow to deep marine succession of the Sierra de Santa Rosa composes the upper part of the Sierra de Santa Rosa Formation that ranges in age from late Sinemurian to early Pliensbachian. Ages of the Permian to Triassic plutonic rocks of northwesternmost Sonora, the Mojave Desert and the Jurassic continental margin Nazas arc that crossed through northern Sonora, are also well recorded by igneous clasts and detrital zircon grains that have been dated from the El Antimonio Group and other Jurassic formations of this region. The upper Oxfordian-lower Tithonian Cucurpe Formation in north-central Sonora recorded the onset of continental extension and incursion of marine waters from the Gulf of Mexico into northwestern Mexico, once activity of the Jurassic magmatic arc ended. [ABSTRACT FROM AUTHOR]

A new model of the junction of the Ural fold belt with the Russian and West Siberian Platforms along the Europrobe Seismic Reflection profiling in the Urals (ESRU) down to a depth of 15 km is constructed. 2Dmodeling of the density and magnetic properties was performed using seven profiles and was accompanied by an estimate of applicability of the method. In the west, the upper part of the model is represented by terrigeneous- carbonate deposits, and the bottom part shows the structures of the basement of the Russian platform, which becomes thinner eastward and plunges beneath the Ural structures. The most significant difference in the West Siberian part of the transect is the great 'length' of the entire structure of the Earth's crust. This is caused by the Early Triassic extension accompanied by the formation of a system of Triassic graben-rifts. [ABSTRACT FROM AUTHOR]

The Early Triassic was a period of ecological restoration for the earth's system after the end-Permian mass extinction. Geochemical records linked to the variations in marine ecosystems during this period have attracted the interest of geologists for many years. Based on petrographic analysis of samples and evaluations of their reliability as proxies for original seawater, this study investigated the carbon and oxygen isotopic compositions of 350 carbonate rock samples from the Lower Triassic (and adjacent strata) in the southern Longmenxia section of Guang'an, eastern Sichuan Basin. The results indicate that the Triassic carbonate rocks from the southern Longmenxia section favorably preserved the original seawater's δ C signal. Furthermore, carbon and oxygen isotopic compositions are found to be poorly correlated, with a determination coefficient as low as 0.0205 and only 44 rock samples show results of Mn/Sr>2 and/or δ O<-6.5‰. The complete carbon isotopic curve for the Lower Triassic is established using the data from the remaining 306 samples with Mn/Sr<2 and/or δ O>-6.5‰. This curve presents favorable comparability on a global scale, specifically in the δ C minima near the Permian-Triassic boundary, at the top of the Jia1 and within the the Jia3, as well as in the δ C maxima at the tops of the Ye1 and Ye4, at the base of the Jia2 and at the top of the Ye3. The peaks and troughs corresponding to these maxima and minima all reflect global signals. By comparing these results to previous research on coeval carbon isotopic curves established within the chronostratigraphic framework, the ages of these critical evolution points are determined. The results show that the Ye1 roughly corresponds to the Griesbachian substage; the Ye2 through Ye4 correspond to the Dienerian substage; Jia1 corresponds to the Smithian substage; from the Jia2 to the lower part of the Jia4 correspond to the Spathian substage; and the middle and upper parts of the Jia4 belongs to the Aegean Substage of the Middle Triassic. Around the boundary between the Jia1 and Jia2 (which represents the Smithian-Spathian boundary (SSB)), the value of δ C increases rapidly from -0.911‰ to 3.679‰. The span during which the seawater's carbon isotope experiences this drastic change may be less than 36 kyr. The oxygen isotope, which is more sensitive to sedimentary environmental changes, exhibits changes prior to the carbon isotope near the SSB, indicating a significant increase in the salinity of the seawater before a sharp rise in the carbon isotope; this event leads to the formation of evaporites and dolomites. [ABSTRACT FROM AUTHOR]

In the context of the harmonisation of the Swiss lithostratigraphic scheme, the Late Ladinian to Early Norian Bänkerjoch Formation and the Norian to Rhaetian Klettgau Formation of northern Switzerland are formally defined. The Bänkerjoch Formation replaces the «Gipskeuper». Delimitation generally follows the traditional Swiss scheme with the onset and offset of sulphate facies as basal and upper boundary. The Klettgau Formation includes six members (from base to top): The Ergolz Member (formerly «Schilfsandstein» and «Untere Bunte Mergel») consists of variegated silty dolomitic marl with dolocretes and channels filled by fine-grained sand of Scandinavian origin. The Gansingen Member (formerly «Gansinger Dolomit s.l.») starts with partly porous dolomite with Carnian bivalves and continues with an alternation of dolomite beds with thin dolomitic marl interlayers. At several places, the member has been eroded to great parts during the Late Triassic. Towards east and southeast, dolomitic sulphates, locally altered to dolomite or limestone, replace the marine carbonates. The Berlingen Member includes coarse alluvial and fluvial sandstones of Vindelician origin. It is restricted to the Lake Constance area. For practical reasons, the Gruhalde Member (formerly «Obere Bunte Mergel» and «Knollenmergel») encompasses all playa sediments above the Gansingen Member and Berlingen Member. Evidence in good outcrops suggests that it consists of several sedimentary cycles separated by long time spans of omission and erosion. The Seebi Member (formerly «Stubensandstein») includes layers of coarse-grained sandstones of Vindelician origin with calcitic, siliceous or clayey matrix. Locally, matrix fraction increases and becomes mostly dolomitic in the upper part. The Belchen Member (formerly «Rhät») consists of partly fossiliferous sandstone and greenish dark marl of estuarine to marine origin. Due to late Triassic and early Jurassic erosion, the Belchen Member is restricted to northwestern Switzerland and the Lake Constance area. [ABSTRACT FROM AUTHOR]

In the context of the harmonisation of the Swiss stratigraphic scheme (HARMOS project), the stratigraphic nomenclature of the Triassic sedimentary succession of northern Switzerland has been reorganised to six formations (from base to top): Dinkelberg, Kaiseraugst, Zeglingen, Schinznach, Bänkerjoch, and Klettgau Formation. The first three are formally introduced in this paper. The Dinkelberg Formation (formerly «Buntsandstein») encompasses the siliciclastic, mainly fluvial to coastal marine sediments of Olenekian to early Anisian age. The formation is some 100 m thick in the Basel area and wedges out towards southeast. The Kaiseraugst Formation (formerly «Wellengebirge») comprises fossiliferous siliciclastic and carbonate sediments documenting a marine transgressive-regressive episode in early Anisian time. It starts with sandstone, dolomite, continues with subtidal limestone and marl and ends with bituminous shale and supratidal dolomite. Thickness decreases from approximately 50 m in the High Rhine area to 10 m in the south and east. In the Lake Constance area, a transition to the siliciclastic marginal facies of the Vindelician High (Eschenbach Formation in Germany) is documented by borehole evidence. The Zeglingen Formation (formerly «Anhydritgruppe») documents a regressive marine evaporitic megacycle during the Illyrian (late Anisian). At most places, except in far eastern Switzerland, it starts with massive halite deposits. It continues with sulfate and marl sequences and ends with littoral stromatolitic dolomite. In the WSW-ENE trending depot centre total formation thickness is 150 m and more, and thickness of salt layers reaches up to 100 m. In the High Rhine area, the thickness is reduced due to subrecent subrosion. At some places evidence points to syn- to early-post-diagenetic erosion. For practical reasons, the six formations are organised in three lithostratigraphic groups: Buntsandstein Group (with the Dinkelberg Formation), Muschelkalk Group (combining the Kaiseraugst, Zeglingen and Schinznach Formations) and Keuper Group (combining the Bänkerjoch and Klettgau Formations). [ABSTRACT FROM AUTHOR]

This work focuses on well-exposed Lower Triassic sedimentary rocks in the area of Torrey (south-central Utah, USA). The studied Smithian [ABSTRACT FROM AUTHOR]