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Member 5 of the Upper Triassic Xujiahe Formation (T3X5) in central Sichuan Basin has made a breakthrough in exploration recently. However, this new stratum has not been investigated sufficiently with respect to basic geology, making its types and distribution of sedimentary facies unclear, which severely restricts its subsequent exploration evaluation. In this study, types of sedimentary microfacies in the first sand group of T3X5 (T3X51) are clarified through core observation and logging interpretation using core, log and seismic data, and then distribution of sedimentary microfacies in T3X51 is determined according to seismic waveform features and seismic prediction. The results show that T3X51 in the Dongfengchang area is mainly composed of deltaic deposits of several microfacies, such as delta front underwater distributary channel, sheet sand, and interdistributary bay. On seismic sections, different microfacies are significantly different in waveform features, the underwater distributary channel is characterized by one trough between two peaks, while diversion bay exhibits chaotic reflections between T6 and T51. The sedimentary microfacies varied greatly during the depositional period of T3X51 in the Dongfengchang area, this is because that the sediment supply was mainly controlled by the southwest and southeast provenance regions. Three superimposed underwater distributary channels are developed in the Dongfengchang area. The phase-1 superimposed underwater distributary channel in the northwest transition to sheet sand in the northeast, the phase-2 superimposed underwater distributary channel in the south extends shortly, the phase-3 superimposed underwater distributary channel in the northeast has a large development scale. These research findings are helpful to guide the subsequent exploration of T3X5 gas reservoir and also theoretically significant for investigating the depositional evolution of the Xujiahe Formation in central Sichuan Basin.

The first results of U–Th–Pb isotope dating of detrital zircons (dZr) from the Chenka sandstones of the Cimmerides of Mountainous Crimea are presented. Carboniferous–Triassic dZr dominate among dZr from Chenka sandstones. Analysis of previously obtained sets of dZr ages from the age and lithologically different formations of Cimmerides of Mountainous Crimea has revealed certain regularities in the change in the time of the provenance signal and, accordingly, of the provenance areas, whose erosion products compose the studied formations. A comparison of the obtained of U–Pb ages of dZr from Chenka sandstones with similar dates obtained for sandstones from the Upper Triassic–Jurassic formations has shown that the provenance signals of the Chenka sandstones and Upper Triassic–Lower Jurassic flysch strata are different, but the provenance signals of the Chenka sandstones and Middle–Upper Jurassic coarse clastic strata are similar. Detrital zircons from the Chenka sandstones show that the parameters of the Th–U distribution in them are intermediate between those from sandstones of flysch and coarse-grained strata, respectively. In general, the isotope-geochronological and geochemical data we obtained and some features of the internal structure of dZr grains from the Chenka sandstones can be used as a strong argument in favor of considering Chenka sandstones as an independent stratigraphic unit with an age not older than the Middle Jurassic. The similarity of the characteristics of dZr grains from sandstones of the Chenka sandstones with those from Middle–Upper Jurassic sandstones casts doubt on the correlations of the Chenka sandstones with a number of lithologically similar units of the southwestern regions of Mountainous Crimea, specified as Early Jurassic in age based on finds of fossil remains. [ABSTRACT FROM AUTHOR]

Previous studies have delved into slope break zones in faulted basins, yet foreland basins, with their gentle slopes toward the forebulge, underdeveloped large-scale structures, and small terrain undulations, have received limited research on slope-fault belts. During the deposition periods of the 4th and 5th members of the Late Triassic Xujiahe Formation, a foreland basin developed in the Sichuan Basin. Scholars have noted the control exerted by the gentle slope break zone on the sedimentary lithofacies in the central and western Sichuan, particularly in the west of the Luzhou-Kaijiang Paleo-uplift, but related studies remain limited. By interpreting the tectonic slope break zones in seismic reflection profiles of the Sichuan Basin and incorporating existing regional geological data, this study employed particle flow numerical simulation to clarify the types of slope break zones in the central and western Sichuan regions, as well as their relationship with gravity sliding structures. It also analyzed the characte-ristics of new types of oil and gas traps associated with gravity-sliding structures. The findings are as follows: (1) The study area developed a fault slope break zone, with each side bounded by a "front squeezing and rear extension" tectonic combinations formed by gravity sliding. The tectonic deformation is weaker than those of gravity-sliding structures at passive continental margins. (2) The edge fault of the tectonic slope break zone controls the sedimentary facies and sand body types. (3) In the gentle slope zone, the stretching area of gravity-sliding structures lead to the uplift of the footwalls of normal faults, forming syndepositional anticlines with developed sandstones. These sandstones, juxtaposed with organic-rich mudstones within the contemporaneous fault depression, form "side-generated and lateral storage" hydrocarbon reservoirs. (4) In the steep slope zone, gravity sliding forms syndepositional anticlines in the 5th member of the Xujiahe Formation, which are bounded by flank mudstones and post-sliding deposited mudstones, forming in-source sand body reservoirs. (5) Syndepositional anticline hydrocarbon reservoirs related to gravity-sliding structures represent a new type of in-source hydrocarbon accumulation. The 5th member of the Xujiahe Formation in the study area likely contains such reservoirs, distributed in a NE-trending pattern parallel to the slope break zone.

The Junggar Basin is known for its high potential of petroleum resources, showcasing significant oil and gas discoveries across various layers. However, the potential of utilizing the thick mudstone of the Upper Triassic as a viable source rock in the basin remains uncertain. Therefore, an urgent need exists to assess the Upper Triassic source rock across the basin and predict the distribution of effective source rocks. This evaluation is crucial for informing future exploration strategies in this layer. To shed light on the spatiotemporal distribution characteristics and hydrocarbon generation potential of the Upper Triassic source rocks in the Junggar Basin, as well as to determine the hydrocarbon generation intensity within the effective hydrocarbon kitchen's distribution range, a comprehensive evaluation was conducted. This evaluation involved assessing organic matter abundance, type, and maturity of the Upper Triassic source rock across the basin using various geochemical parameters derived from data collection, profile measurement, drill cuttings observation and sampling, and organic geochemistry testing. Key parameters were then selected, and a multi-level fuzzy mathematical evaluation method was employed to map out the development range of the effective hydrocarbon kitchen. The findings indicate that the Upper Triassic source rock exhibits a broad distribution range spanning the entire basin, with considerable thickness (reaching up to 350 m) and significant burial depth in the central region (up to 11 000 m). The total organic carbon (TOC) content of source rocks varies from 0.75% to 8.30%, with an average value of 1.74%. Additionally, the average values of S1+S2 and chloroform asphalt "A" are 2.78 mg/g and 0.354%, respectively. The predominant organic matter types in the area are type Ⅲ and type Ⅱ2, indicating a dominance of terrestrial higher plant inputs. The favorable kerogen types are primarily located from the western sag to the Fukang Sag. The thermal evolution of the organic matter ranges from low-maturity to mature stages, with some areas reaching high to over-maturity levels. As per the evaluation criteria for hydrocarbon generation potential of coal-bearing mudstone in China, the Upper Triassic mudstone generally represents poor to medium-quality source rocks with significant hydrocarbon generation potential, particularly for gas. The key hydrocarbon source kitchens are situated from the western part of the Fukang Sag to the eastern part of the Shawan Sag in the central depression, and in the Huomatu Anticline of the southern margin thrust belt. Within these areas, the Ro value of the source rock exceeds 1.3%, with oil and gas generation intensities reaching 50×104 t/km2 and 3×108 m3/km2, respectively.

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For the first time, this study presents interpretations of alluvial fans in spectral decomposition RGB Blends, analysed in seismic time slices from the Middle Triassic to Lower Jurassic stratigraphical interval of the Horda Platform (northern North Sea). The time slices record a shifting alluvial fan front, fluvial variability, uplift and erosion and reveals depositional elements that may set the common conception of the geological development of this area during the Early–Middle Mesozoic up for discussion. Results show that the Upper Triassic Lunde Formation in the eastern margin of the Horda Platform was characterized by the deposition of coalesced alluvial fans. A variable extent of the fan front through the Upper Triassic is linked to interplaying allogenic factors: uplifted source areas in the aftermath of Early–Middle Triassic rifting determined sediment availability; climate transitioning from arid to semi‐humid, with increasingly fluctuating precipitation, controlled sedimentation, and run‐off; provenance dictated bulk sedimentology and affected prevailing alluvial processes. An overall retreat of the fan system through the Late Triassic coincided with a significant change in landscape characteristics at the transition into the overlying Statfjord Group. Uplift and initial tilting of the Horda Platform caused landscape degradation and the formation of plateaus and incised valleys, contemporaneous with increased humidity and marine transgression, forming estuaries. The shift in depositional style has implications for reservoir properties, creating complexity and heterogeneity in terms of facies distribution and connectivity, which may benefit potential CO2 storage. Upper Triassic alluvial fan development in the Horda Platform (northern North Sea) depicted through spectral decomposition of seismic time slices Enhanced level of seismic stratigraphic interpretation with RGB blending Impact of allogenic factors on alluvial depositional development Implications of alluvial variability on reservoir properties [ABSTRACT FROM AUTHOR]

The Qadir coal-bearing member of the Rhaetian Nayband Formation in the Parvadeh coal mine, East-Central Iran, was investigated for palaeoenvironmental reconstruction to predict coal properties. Along with field studies, rock petrography, XRD, and SEM-EDX analyses were carried out, and petrofacies, lithofacies, and facies associations were defined in a sequence stratigraphic framework. These studies represent a river-dominated, storm- and wave-influenced coastal/delta plain setting that accumulated along the shallow marine environment. The studied Qadir member is part of a paralic system that consists of progradational delta grading into shallow marine siliciclastic shelf sediments. Apart from sea-level fluctuations, the sedimentary pattern was mainly governed by tectonic events in a post-orogenic foreland setting connected to the rising Cimmerian Mountain range in the north. Sedimentological analysis and stacking patterns of the Qadir member indicate that discrete coal seam and zones in the member were formed by peat mires that extended onto the delta plain and occurred in fourth-order sequences stacked in the transgressive system tracts of the lower sequence (TST1) and early highstand systems tract of the upper sequence (HST2). However, the main economic coal zone was formed in the lower delta plain environment, predominantly within the middle part of the TST. The detrital nature and composition of the numerous partings and high ash content in the coal seams indicate that the coal-forming environment was a low-lying, topogenous flow-fed mire near detrital sources (i.e. distributary channels). Seemingly, coal layers are thicker with less sulfur (pyrite), but more ash toward the western part of the area. [ABSTRACT FROM AUTHOR]

Mesozoic marine shale oil was found in the Qiangtang Basin by a large number of hydrocarbon geological surveys and shallow drilling sampling. Based on systematic observation and experimental analysis of outcrop and core samples, the deposition and development conditions and characteristics of marine shale are revealed, the geochemical and reservoir characteristics of marine shale are evaluated, and the layers of marine shale oil in the Mesozoic are determined. The following geological understandings are obtained. First, there are two sets of marine organic-rich shales, the Lower Jurassic Quse Formation and the Upper Triassic Bagong Formation, in the Qiangtang Basin. They are mainly composed of laminated shale with massive mudstone. The laminated organic-rich shale of the Quse Formation is located in the lower part of the stratum, with a thickness of 50–75 m, and mainly distributed in southern Qiangtang Basin and the central-west of northern Qiangtang Basin. The laminated organic-rich shale of the Bagong Formation is located in the middle of the stratum, with a thickness of 250–350 m, and distributed in both northern and southern Qiangtang Basin. Second, the two sets of laminated organic-rich shales develop foliation, and various types of micropores and microfractures. The average content of brittle minerals is 70%, implying a high fracturability. The average porosity is 5.89%, indicating good reservoir physical properties to the level of moderate–good shale oil reservoirs. Third, the organic-rich shale of the Quse Formation contains organic matters of types II1 and II2, with the average TOC of 8.34%, the average content of chloroform bitumen ‘A’ of 0.66%, the average residual hydrocarbon generation potential (S1+S2) of 29.93 mg/g, and the Ro value of 0.9%–1.3%, meeting the standard of high-quality source rock. The organic-rich shale of the Bagong Formation contains mixed organic matters, with the TOC of 0.65%–3.10% and the Ro value of 1.17%–1.59%, meeting the standard of moderate source rock. Fourth, four shallow wells (depth of 50–250 m) with oil shows have been found in the organic shales at 50–90 m in the lower part of the Bagong Formation and 30–75 m in the middle part of the Quse Formation. The crude oil contains a high content of saturated hydrocarbon. Analysis and testing of outcrop and shallow well samples confirm the presence of marine shale oil in the Bagong Formation and the Quse Formation. Good shale oil intervals in the Bagong Formation are observed in layers 18–20 in the lower part of the section, where the shales with (S0+S1) higher than 1 mg/g are 206.7 m thick, with the maximum and average (S0+S1) of 1.92 mg/g and 1.81 mg/g, respectively. Good shale oil intervals in the Quse Formation are found in layers 4–8 in the lower part of the section, where the shales with (S0+S1) higher than 1 mg/g are 58.8 m thick, with the maximum and average (S0+S1) of 6.46 mg/g and 2.23 mg/g, respectively.

Abstract Peat forming environment strongly influences the economic value of any coal seam and coal-bearing strata. Hence, palaeoenvironmental studies provide important information for coal resource exploration. In this context, detailed studies on selected coals from the Parvadeh Area, Iran, were conducted using sedimentology, coal petrology, X-ray diffraction (XRD), scanning electron microscopy- energy dispersive X-ray analyzer (SEM-EDX), and proximate analysis. The sedimentary facies above and below the coal seams are mainly marine or marine-influenced facies, supporting that the coal-forming mires in the Parvadeh Area developed in a paralic environment, where the base level must be closely related to sea level. Sulfur contents are moderate to high and mark the influence of brackish/marine water, especially during transgression after peat growth in a lower delta plain environment. The peat-forming mires extended on coastal/delta plain lobes. The lower delta plain/coastal plain coals are characterized by lateral continuity and substantial thickness, whereas few coals possibly representing the upper delta plain are thin and more discontinuous. The detrital nature and composition of the numerous partings and the overall high ash yield in the coal seams indicate an active tectonic area with high rates of creation of accommodation space over peat growth. Coal petrology and coal facies analysis exhibits a permanently high water table within a forest swamp and mostly rheotrophic conditions, sometimes with connection to the seawater. According to paleoenvironmental reconstructions, it seems that coal layers may be thicker, with less sulfur (pyrite), but more clastic minerals and partings toward the western part of the area. Although these coal seams presently have low economic potential for the mining operation, partly due to great depth, this humic, high-volatile to medium-volatile bituminous coal may be suitable for exploration of coal bed methane resources.

Copyright of Geology & Resources is the property of Geology & Resources Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Peat forming environment strongly influences the economic value of any coal seam and coal-bearing strata. Hence, palaeoenvironmental studies provide important information for coal resource exploration. In this context, detailed studies on selected coals from the Parvadeh Area, Iran, were conducted using sedimentology, coal petrology, X-ray diffraction (XRD), scanning electron microscopy- energy dispersive X-ray analyzer (SEM-EDX), and proximate analysis. The sedimentary facies above and below the coal seams are mainly marine or marine-influenced facies, supporting that the coal-forming mires in the Parvadeh Area developed in a paralic environment, where the base level must be closely related to sea level. Sulfur contents are moderate to high and mark the influence of brackish/marine water, especially during transgression after peat growth in a lower delta plain environment. The peat-forming mires extended on coastal/delta plain lobes. The lower delta plain/coastal plain coals are characterized by lateral continuity and substantial thickness, whereas few coals possibly representing the upper delta plain are thin and more discontinuous. The detrital nature and composition of the numerous partings and the overall high ash yield in the coal seams indicate an active tectonic area with high rates of creation of accommodation space over peat growth. Coal petrology and coal facies analysis exhibits a permanently high water table within a forest swamp and mostly rheotrophic conditions, sometimes with connection to the seawater. According to paleoenvironmental reconstructions, it seems that coal layers may be thicker, with less sulfur (pyrite), but more clastic minerals and partings toward the western part of the area. Although these coal seams presently have low economic potential for the mining operation, partly due to great depth, this humic, high-volatile to medium-volatile bituminous coal may be suitable for exploration of coal bed methane resources. [ABSTRACT FROM AUTHOR]

Natural fractures are quite important for the high and stable production of tight sandstone gas reservoirs. However, it is commonly difficult to accurately characterize their distribution in tight sandstone gas reservoirs due to the strong heterogeneity. A comprehensive characterization of natural fractures in tight sandstone gas reservoirs of the Xujiahe Formation in the Yuanba area, Sichuan Basin, was carried out by multimethod of core description, log interpretation and seismic prediction. The results show that (1) the natural fractures in the Xujiahe Formation are mainly low-angle fractures, with a few medium- and high-angle fractures. The degree of fracture development is mainly controlled by the distance from the fault, the flexural degree of the strata and the thickness of the rock mechanical layer. (2) The fracture-sensitive seismic attributes such as the preferred maximum likelihood, structure entropy, illuminant-based symmetry and high-precision curvature are taken as the input, and the unsupervised cluster analysis algorithm based on Bayesian probability model is applied to predict the distribution of large-scale fractures at different dip angles; on the basis of narrow azimuthal pre-stack CMP gather optimization, the anisotropy detection technique of Hampson-Russell's ProAZ full CMP gather is used to characterize the distribution of small- and medium-scale fractures, and the predicted fracture development intensity matches the fracture interpretation results of the imaging logs by more than 85%. Moreover, the predicted fracture orientation is basically consistent with that of the imaging loggings. (3) The fault-genesis fractures of the Xujiahe Formation are mainly distributed near the fault on the southeast flank of the Jiulongshan anticline, and are distributed in a narrow strip in NE direction. The fold-genesis fractures are mainly developed in the Xu 3rd Member, and are located in the axis of the Jiulongshan anticline and its southeast flank where the strata are strongly flexed. This study provides a solid foundation for the development of tight sandstone gas reservoirs and extends the approaches for the accurate characterization of fractures.

The Upper Triassic Xujiahe Formation (T3x) is the most important terrigenous stratum in the Western Sichuan Depression; however, it is still insufficient for the understanding of molecular compositional characteristics of its source rocks. Based on the analysis of both saturated and aromatic fractions of extracts of source rocks from different members of the Xujiahe Formation, the indication is then discussed for sedimentary environment and thermal evolution of source rocks. The distribution of tricyclic terpanes (TTs) and dibenzothiophene/phenanthrene (DBT/P) ratio of the argillaceous source rocks in 2nd to 4th members of the Xujiahe Formation mainly display the signatures of typical lacustrine source rocks, and the relatively high gammacerane/C30 hopane (0.16-0.23), as well as 9-/1-methylphenanthrene (1.16-1.41) ratios suggest relatively high salinity of water body. The parameters such as methylphenanthrene index (MPI1), methylphenanthrene distribution fraction (F1), and methyldibenzothiophene distribution index (MDBI) are effective for the evaluation of thermal maturity, and they show positively and negatively linear correlation with maturity degree before and after Ro=1.35%. The distribution pattern of C27-C29 regular steranes, relative composition of three fluorine series, and methyldibenzothiophene/methyldibenzofuran ratios for high to over-maturity T3x source rocks are distorted due to the effect of thermal maturation.

Copyright of Journal of Northeast Petroleum University is the property of Journal of Northeast Petroleum University Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Geometric morphometric approaches become increasingly applied in the fields of biology and palaeontology. Taxonomy is a good example, where a long‐standing intention of scientists is to eliminate subjectivity as much as possible. In the case of biostratigraphically important conodont elements, the application of such methods is not widespread. Only a handful of studies attempted to deal with the morphological variance of conodont elements from this aspect. The detailed description of five lower Norian (Upper Triassic) taxa (Ancyrogondolella quadrata, A. rigoi, A. triangularis, A. uniformis and Metapolygnathus mazzai) is presented here based on landmarks and Fourier analysis of the P1 element and keel outlines. Both methods led to similar outcomes regarding taxonomic differentiation and exposing shape variability. Consensus shapes were generated to objectively reveal the typical contour shape of each taxon, which allowed their comparison with each other, and with the members of their respective sample population including the holotypes. The results demonstrated that the holotype of a taxon is generally not an average representative, but rather a peripheral form with well separable morphological characteristics. Ancyrogondolella quadrata and A. rigoi turned out to represent a morphological continuum with ample transitional forms between these two end‐members that may cause bias in their biostratigraphic applicability, however their combined shape variance seems to be too large for uniting them into a single species. Given the results that may be too subtle to realize based solely on qualitative observations, future taxonomic studies and type material designation could greatly benefit from the application of similar methodologies. [ABSTRACT FROM AUTHOR]

The Upper Triassic conodont genus Primatella is important for recognizing the Carnian-Norian stage boundary in Panthalassan and Tethyan domains. Originally based on Canadian material from Black Bear Ridge in the Western Canada Sedimentary Basin, two key species are highlighted, and their occurrence is documented in the allochthonous Wrangellia and Alexander terranes in the North American Cordillera; in the Great Basin in Nevada, western United States; at Pizzo Mondello, Sicily, in western Tethys; and in Timor-Leste on the southeastern margin of the Meso-Tethys Ocean (northeastern Gondwana). The correlation potential of Primatella species is compromised by a differing nomenclature employed in Tethyan regions of Europe where Primatella species have been assigned to other genera, namely, Ancyrogondolella (formerly Epigondolella), Carnepigondolella, and Metapolygnathus. This has obscured phyletic relationships and impacted the stratigraphic utility of two demonstrably cosmopolitan species, P. asymmetrica and P. bifida. These species are shown to occur widely in a variety of paleoenvironments and have a restricted stratigraphic range around the CNB for which they can be adopted as useful indices.

The relatively recent discovery and contextualization of silesaurid and lagerpetid dinosauromorphs has led to a revolution in understanding the early evolutionary history of the dinosaurian lineage. Lagerpetids are known from North America and South America in Middle and Upper Triassic rocks, especially the Chinle Formation of New Mexico and the Dockum Group of Texas. Until now, only a single specimen of Dromomeron gregorii was known from the Upper Triassic Chinle Formation of Arizona. However, a new lagerpetid astragalus specimen (MNA V7237) from the Owl Rock Member of the Chinle Formation found on Ward Terrace in the Navajo Nation of Arizona is referred to Dromomeron romeri. MNA V7237 represents the youngest radioisotopically-dated record of Lagerpetidae, indicating that D. romeri persisted throughout the entire Norian (Otischalkian into the Apachean) in North America.

Der Gattungsnamc Cucurbita Jablonsky, 1973 kann nicht als gueltig betrachtet werden, da dieser Name bereits 1882 durch Scudder (Nomenclator Zool. Suppi. Lise, 93) an eine Muschel­Gattung vergeben worden ist. Die Gattung Pseudocucurbita Borza & Samuel, 1978 wird mit der Gattung Cucurbita synonym erkliirt. Da der Name Cucurbita hinfaellig ist, wird der Name Cucurbita Jablonsky durch Pseudocucurbita Borza & Samuel (pro Cucurbita Jablonsky) ersetzt (Homonymie).

A new outcrop with Rhaetavicula contorta was found on the northeast slope of the M. Ponciv, at Pra Brusché (1065 m s.l.m.). The outcrop has the same lithologic characters of the typical « Avicula contorta levels » but its faunal content is quite peculiar. Microfauna and macrofauna were examined in detail and the results compared with the bibliographic data relevant to the « Avicula contorta levels ».

The Coastal Cordillera of Central Chile (34°–37°S) holds a series of Late Triassic granitoids classically interpreted as early Andean subduction‐related magmatism based on their arc‐like geochemical signature. Here, we present geochemical, isotopic, and geochronological data and a tomotectonic analysis that challenge this idea indicating a local interruption of the normal subduction process likely associated with a slab‐tearing event. Our results suggest that the source of the magmas is related to melting of asthenospheric mantle and crustal rocks of a metasedimentary Paleozoic complex. We suggest that partial melting of these sources was triggered by a slab tear‐related asthenosphere upwelling producing high‐silica S/I‐ and S‐Type granites of the Constitución and Hualpén areas, and anorogenic A‐Type granitoids in Cobquecura area. Also, partial melting of a metasomatized asthenospheric mantle plus continental crust that experienced previous high‐temperature hydrothermal alteration would have generated high‐silica magmas with low δ18O, high Pb, CHUR‐like 87Sr/86Sr, and 143Nd/144Nd ratios that originated La Estrella Granite. Our results offer an alternative explanation for the existence of subtle magmatic arc‐like geochemical signatures in the study area and support a segmentation of the active margin during the Late Triassic. The widespread upper‐plate magmatic record of slab‐tearing, spanning the Coastal Cordillera of Central Chile to the intraplate Neuquén basin in Argentina, and the lower mantle record of a slab gap, detected in ours and previous tomotectonic analyses, make the Late Triassic slab‐tearing event in southwestern Pangea the most robustly constrained pre‐Cenozoic slab tear process so far. Key Points: The Late Triassic granitoids of Southern‐Central Chile were emplaced from 220 to 210 MaS, S/I, and A‐type granites characterize Late Triassic magmatismSlab‐tearing was likely the driver for granite generation in Southern‐Central Chile [ABSTRACT FROM AUTHOR]

A new Mystriosuchinae phytosaur, Colossosuchus techniensis, is described from the Upper Triassic Tiki Formation of India. Colossosuchus is diagnosed by multiple apomorphies, including a strongly downturned terminal rosette (c. 70°), closely spaced mediolateral band‐like ornamentation on dorsal surface of the nasal, dorsolaterally oriented supratemporal fenestra, ventrolaterally inclined postorbital–squamosal bars depressed below the skull table, dorsally convex parietal–squamosal bar that descends ventrolaterally below the skull roof, dome‐shaped skull in lateral view, prominent neural arch laminae and fossae, three sacral vertebrae, robust proximal end of the tibia, and fibula with high anteroposterior flaring of the distal end. The total body length of the largest individual recovered from the bonebed is estimated to be more than 8 m, suggesting that Colossosuchus is one of the largest phytosaurs known. Phylogenetic analysis nests Colossosuchus and other undescribed specimens from India within Mystriosuchinae. These form a distinct clade and represent the earliest record of endemism among Gondwanan phytosaurs. This clade is recovered as sister taxa to ((Volcanosuchus + Rutiodon) + Leptosuchomorpha), where the depressed supratemporal fenestra first appeared in the phytosaur lineage, a feature previously used to diagnose the derived leptosuchomorphs. Early‐diverging phytosaur diversification may have coincided with the final stages of the Carnian Pluvial Event with their possible migratory routes along the circum‐Tethyan coastline. The lineage continued to evolve mostly through endemic radiations and experienced an extinction event during early Norian, which marked the disappearance of most of the non‐leptosuchomorph taxa. This is attributed to post‐CPE aridification, although more study is required. [ABSTRACT FROM AUTHOR]

The Puesto Viejo Group is an important unit for the knowledge Triassic faunas especially non-mammalian therapsids. This group crops out in the San Rafael Block, southwest Mendoza, Argentina. It is composed of the basal Quebrada de los Fósiles Formation (QF) which is overlaid by the Río Seco de la Quebrada Formation (RSQ). This report comprises tetrapod remains from the RSQ Formation at the Quebrada del Durazno area that includes, until now, exclusively therapsids. The aim of this study is to analyse the bone microstructure of cynodonts and dicynodonts to elucidate the histological features and growth patterns. Histological thin sections made in ribs and appendicular bones reveal a predominance of fibrolamellar bone tissue suggesting an overall fast bone growth, however, the presence of parallel-fibred bone suggest periods of slowing down of the growth. The existence of growth marks indicates periodic interruptions of growth, which is likely the expression of their ability to rapid respond to environmental changes. This contribution offers new insights into the bone microstructure of tetrapod assemblages from RSQ Formation during the Upper Triassic span. [ABSTRACT FROM AUTHOR]

The Norian "chaotic carbon episode" stands out as a compelling carbon cycle perturbation event within the Late Triassic period. This episode has been documented in marine stratigraphic sections across North America, Italy, Japan, and China. However, limited Norian chronostratigraphy available in the eastern Tethys inhibited the identification of this event in this broad area, and thus the possible global response to this carbon cycle perturbation. To address this issue, we analyzed the conodonts and carbon-isotope of the Norian Sanhedong (SHD) section in the Simao terrane, Southwest China. The identification of the Alaunian Epigondolella spiculata Zone has well documented the base of the Alaunian stage. Moreover, a conodont faunal turnover can be recognized at the base of the Alaunian, with the evolution of Mockina from Ancyrogondolella and Epigondolella , and it is characterized by a gradual decrease in specimen size. The E. spiculata conodont Zone from the SHD section correlates well with the homonymous conodont Zones documented in both the Tethys and the Panthalassa Oceans. Two carbon-isotope negative excursions (CIE1 and CIE2) have also been recorded in the Lacian to Alaunian of the SHD section that can be compared with coeval global sections. • In this study, the typical Alaunian conodont Epigondolella spiculata Zone has been identified in the eastern Tethys. • The descendants of the genus Ancyrogondolella show a significant reduction in size from the Lacian-Alaunian transition. • Two carbon-isotope negative excursions (CIEs) described in the SHD section can be correlated with global coeval sections. [ABSTRACT FROM AUTHOR]

The Triassic was a critical period for a significant increase in the generic diversity of radiolarians after the disappearance of >80% of radiolarian genera during the Permian-Triassic mass extinction. In particular, the Upper Triassic radiolarian fauna is rich and has been documented in several world regions, such as North America, Western Europe, the Mediterranean area, Japan, the Philippines, Timor, and Far East Russia. In this study, a well-preserved and high-diversity fauna from a continuous pelagic-hemipelagic section deposited in western Tethys (Sicily, Italy) provides one of the most detailed radiolarian records of the Carnian-Norian boundary interval, which can be correlated worldwide, from high to low-latitude, from both sides of the Pangea and both Hemispheres. The 99 species belonging to 50 genera from this time interval have been collected from the Pizzo Mondello section (Sicanian Basin, Western Sicily), the selected GSSP for the base of the Norian stage, and then compared to the radiolarian associations documented in other coeval regions. Based on the occurrences of characteristic radiolarian species, we defined and proposed a new radiolarian biozonation across the Carnian-Norian boundary, which consists of five new assemblages (PM assemblage 1–5) that are correlated and calibrated to the already well-defined biozonation of bivalves, ammonoids, and conodonts. • The study proposes a new radiolarian biozonation across the Carnian/Norian boundary (CNB) from the Norian GSSP section. • The new radiolarian assemblages are calibrated to bivalves, ammonoids, and conodonts zonation and compared to coeval regions. • This study provides new insights into the radiolarian biostratigraphy, radiation, and evolution across the global CNB interval. [ABSTRACT FROM AUTHOR]

The distribution and genetic mechanisms of connected pore systems in continental shale reservoirs were analyzed in this paper to enhance the high-efficiency exploration of shale gas. A case study was made with the continental shale of the Upper Triassic Xujiahe Formation in the Western Sichuan Depression. Various experimental methods such as X-ray diffraction, field emission-scanning electron microscopy, low temperature gas adsorption, high-pressure mercury injection and nuclear magnetic resonance cryoporometry were applied to study its mineral composition, distribution of pore-size and pore connectivity, and the main constrains for pore connectivity were discussed. The continental shale of the Xujiahe Formation in the study area has a high content of clay minerals, followed by quartz. The pore-size distribution is complex, and the mesopores in the range of 4-50 nm is the main contributor to pore volume (87.33%) and specific surface area (49.19%). The pores having the size between 20-50 nm appeared to have better pore connectivity and are the major type of connected pores. The continental shale developed various types of pore, predominantly composed of clay intercrystalline pores, with minor dissolved pores and organic pores. Microfractures were widely developed and formed the dominant connective pore assemblage together with clay intercrystalline pores. The development and distribution of connected pores were controlled by the contents and arrangement of brittle minerals such as clay minerals and quartz. Based on the experimental results, some development mechanisms of connected pores in continental shale were concluded. The combination of intercrystalline pores and microfractures developed on the matrix of clay minerals and brittle minerals shows the best connectivity, followed by the clay intercrystalline pores in clay minerals, while the organic pores and clay intercrystalline pores in organic-clay complexes show the lowest connectivity.

The Zhangjiatan oil shale from the Upper Triassic Yanchang Formation in the southern Ordos Basin is an important solid mineral resource, it can also be considered as the main source rock of Triassic oil and gas in the basin. Results of analytical experiments such as TOC, bitumen extraction and group composition, oil content etc. of shale samples from key typical outcrop sections and drilling cores showed that the Zhangjiatan oil shale has a high organic matter abundance. The TOC content ranges 5.11% to 36.47%, with an average value of 16.15%. The S0+S1+S2 value distributes between 16.58-230.98 mg/g, with an average value of 94.20 mg/g. The extracted bitumen abundance is between 0.42%-2.22%, with an average value of 1.25%. Based on these analytical results, Zhangjiatan oil shale can be assigned to be high-quality source rock with an excellent hydrocarbon generation potential. The oil content of oil shale is between 3.52% and 14.6%, with an average value of 8.16%, which belongs to medium- and high-quality oil shale. The kerogen type is mainly Ⅰ-Ⅱ1, and the Ro value generally ranges from 0.43% to 1.09%. Based on field outcrop and drilling core samples, a thermal evolution profile of the Zhangjiatan oil shale in the southern Ordos Basin was established. Moreover, the oil contents of oil shale before and after solvent extraction were compared, and the variations of oil content and pyrolysis hydrocarbon products during the thermal evolution of oil shale were analyzed. There are two types of resources such as oil shale and shale oil in the Zhangjiatan oil shale with a great potential in the southern Ordos Basin. Moreover, some exploration and development countermeasures of oil shale and shale oil were put forward.

The Upper Triassic Dockum Group of Garza County, Texas (lower, middle, and upper Cooper Canyon Formation) captures the radiation of Triassic non-marine tetrapods by preserving a variety of Late Triassic taxa from the southwestern United States. Our understanding of the vertebrate assemblage from these strata largely comes from a single site, the Post Quarry (lower Cooper Canyon Formation), with previous research documenting a variety of temnospondyls, sphenodontians, non-archosauriform archosauromorphs, and archosauriforms including a phytosaur, three species of aetosaurs, a poposauroid, a rauisuchid, a crocodylomorph, and several dinosauromorphs. To more completely reconstruct the vertebrate assemblage of the Dockum Group of Garza County we use an apomorphy-based approach to identify morphologically similar disarticulated and fragmentary elements from a variety of localities that span the entire Cooper Canyon Formation (Norian-Rhaetian), allowing assignments from the large clade level to the species level. Many skeletal elements are incomplete yet diagnostic and are assigned to the least inclusive clade if discrete character states do not allow for an unambiguous species-level identification. We identify new specimens referable to numerous clades including Tanystropheidae, Allokotosauria + Prolacerta + Archosauriformes, Vancleavea + Litorosuchus, Phytosauria, Paracrocodylomorpha, Dinosauriformes, and Saurischia, in addition to additional species identifications of the aetosaur Scutarx deltatlyus, and the dinosauromorph Dromomeron gregorii. Our study of this material demonstrates the utility of an apomorphy-based approach in making testable and repeatable observations for identifying small, isolated fragmentary fossil tetrapod material to reconstruct a more accurate faunal hypothesis for a portion of the Late Triassic of Texas. Previous claims of the earliest dinosaurs from near the base of the Dockum Group do not pass the apomorphy-based identification test, and the question of whether the oldest known North American dinosaurs are present in the Chinle Formation or Dockum Group can be resolved by utilizing vertebrate biostratigraphic correlation. Our revision of these fossil assemblages supports the hypothesis that early diapsids, early archosauromorphs, and non-dinosaurian dinosauromorphs were more common, diverse, and widespread in low latitudes during this time than previously thought.

The Upper Triassic Xiaotangzi and Xujiahe formations are important gas exploration targets in the Sichuan Basin. This article, based on a systematic analysis of sandstone clastic framework components, depositional structures, clay minerals, trace elements and organic geochemistry, gives a detailed discussion regarding their sedimentary environment. There exist abundant tide‐generated depositional structures in this sequence, and the sedimentary provenance was dominated by a recycled orogen belt in the north and by a continental block at an early stage then recycled orogen belt at the late stage in the south of the western Sichuan Basin. The Xiaotangzi Formation and members 2–3 of the Xujiahe Formation only have authigenic illite and chlorite. In contrast, members 4–6 contain increasing kaolinite and decreasing illite and chlorite from bottom to top. The water column salinity gradually downgraded from hyperhaline, euhaline and polyhaline of the Xiaotangzi Formation to member 2 to polyhaline and mesohaline of members 3–6. The source rocks of the Xiaotangzi and Xujiahe formations have a generally low Pr/Ph, minus the value of (Pr/nC17)‐(Ph/nC18), and high values of Pr/nC17 and Ph/nC18. They also show apparent dominance of 9‐MP in methylphenanthrene composition and different point groups of fluorenes, dibenzofurans and dibenzothiophenes from marine or salt lake facies, as well as typical swamp facies. In conclusion, the Xiaotangzi Formation and members 2–3 were deposited in a marine environment, whereas members 4–6 were deposited mainly in a transitional to the continental environment. [ABSTRACT FROM AUTHOR]

The Chang 7 member of the Upper Triassic Yanchang Formation is an important source rock in the Ordos Basin, NW China. Previous studies of the unit have in general focused on the relatively deep‐water (∼25 m) anoxic, OM‐rich lacustrine mudstones which form the main Mesozoic source rock at fields in the south of the basin. However, this paper presents an integrated geochemical investigation of the relatively shallow‐water Chang 7 facies in a study area around Jiyuan field in the western part of the basin in order to evaluate its source rock potential. The results show that the Chang 7 source rock in the study area has a high content of Type II OM, and is interpreted to have been deposited in a suboxic‐anoxic lacustrine setting with a mixed input of aquatic and terrigenous organic matter. The results of 1D modelling of a well in the study area showed that the Chang 7 member entered the oil generation window from the Middle Jurassic. Oil‐oil correlations based on hierarchical cluster analysis and correspondence analysis showed that crude oils generated by deep‐water Chang 7 source rocks from wells in the south of the basin can be distinguished from Soxhlet‐extracted petroleum from reservoir sandstones in the study area. The compositional differences are inferred to be due to variations in source rock facies compositions. An oil – source rock correlation study showed that the shallower‐water Chang 7 source rock in the western part of the basin generated the hydrocarbons in core extracts of reservoir sandstones from wells in this area. The shallow‐water Chang 7 facies may therefore constitute an effective oil‐prone source rock in the western Ordos Basin. [ABSTRACT FROM AUTHOR]

Fossil deposit first described by Franz Toula in 1890, in the Garnyovitsa area near Kotel is estimated as a geosite of a national significance with historical value for the Bulgarian geology. Here is cropping out a huge marl olistolith embedded among Middle Jurassic turbidites of the Kotel Olistostrome Formation. It contains Late Triassic (Norian) hydrozoa and corals, identified by the first explorers of the Bulgarian lands as early as the end of the 19th century. Given the high geodiversity of the area and the proximity to Kotel, this geosite has great potential for geotourism within the future geopark "East Balkan". [ABSTRACT FROM AUTHOR]

We have investigated the tectonic and erosion features of the Upper Triassic (Mulussa F Formation) and Lower Cretaceous (Rutbah Formation) sediments in the Euphrates graben area and analysed their influence on changes in the thickness and zonal distribution patterns of these sediments. In this study, the geological modeling software of Petrel Schlumberger is used to model the regional geological structure and stratigraphy from the available geological and geophysical data.The Upper Triassic and Lower Cretaceous sediments (in total, almost 800 m thick) are the major hydrocarbon reservoirs in the Euphrates graben, which contain approximately 80 to 90 % of the total hydrocarbon reserve in this area. These sedimentary zones experienced variable changes in thickness and zonal distribution due to erosion processes caused by the two major regional unconformities, the Base Upper Cretaceous (BKU) and Base Lower Cretaceous (BKL) unconformities. The maximum thickness of the Upper Triassic sediments amounts to 480 m in the central parts of the Euphrates graben and along the NW-SE trend, i.e. in the dip direction of the Upper Triassic Mulussa F Formation. Towards the NE flank of the graben near the Khleissia uplift and the SW flank near to the Rutbah uplift, the thickness of the Upper Triassic sediments is gradually decreased due to their partial or total erosion caused by the BKL unconformity, and also due to a less space for sediment accumulation near the uplifts. The thickness of the Lower Cretaceous sediments increases in the northern, NW and NE flanks of the graben. Their maximum thickness is about 320 m. The BKL unconformity is the major cause of erosion of the Lower Cretaceous sediments along the southern, SE and SW flanks of the graben. In the Jora and Palmyra areas towards the NW flank of the Euphrates graben, the Upper Triassic and Lower Cretaceous sediments show no changes in thickness. In these areas, there was more space for sediment accumulation, and the sediments were less influenced by the BKL and BKU unconformities and thus less eroded.

The Euphrates Graben is located in eastern Syria. The Upper Triassic Mulussa F Formation sandstones serve as the primary reservoir intervals in the majority of the graben fields. The study's findings were based on core studies: petrographic examination of thin sections, scanning electron microscope (SEM), imaging of backscatter scanning electron microscope (BSE), X-ray microprobe examinations, and carbon-oxygen stable isotope analysis of microfracture-filling cements. Three of the most common types of microfracture found in the investigated sandstones are intragranular or intracrystalline microfractures, grain boundary or grain-edge microfractures, and transgranular (crossing grains) microfractures. Sandstone microfractures that are open and free of secondary mineralization improve sandstone storage and permeability. However, microfractures that are cemented and filled with secondary mineralization reduce storage and permeability. Common siderite and pyrite cements were identified within the microfractures and the nearby sandstone matrix. Larger anhedral or euhedral siderites are thought to form during shallow burial diagenesis, whereas poikilotopic siderites are thought to form during deep burial diagenesis. Poikilotopic pyrite is believed to be a diagenetic cement, which is attributed to the reduction of iron oxides present in the sediments in the presence of hydrocarbons. Microfractures reflect tectonic, overpressure, and diagenetic origins. Microfractures of tectonic origin are associated with folding and thrust activities over the Euphrates Graben area, and they were formed at the beginning of the Upper Triassic with siderite and pyrite cement equilibration temperatures of approximately 100–105 °C, and they continued forming from the middle to the end of the Upper Triassic with cement equilibration temperatures of approximately 90–100 °C in conjunction with the first phase of the Euphrates Graben. Microfractures related to diagenetic and overpressure processes are tension microfractures and were formed in compression settings during the Upper Triassic. [ABSTRACT FROM AUTHOR]

Upper Triassic carbonate platforms from the Panthalassa Ocean remain less-understood and less-studied than their Tethyan equivalents. This imbalance is largely due to the poorer preservation state of Panthalassan carbonate rock successions in terms of rock quality and depositional geometries, which prevents good appreciation of depositional systems. In this context, carbonate exposures from Lime Peak (Yukon, Canada) represent an outstanding exception. There, the remains of an Upper Norian Panthalassan carbonate platform are well-exposed, show remarkably preserved depositional geometries and overall superior rock preservation. In this work, we analyse the carbonates from the Lime Peak area with particular attention to the vertical and lateral distribution of biotic assemblages and microfacies at the platform scale. Results demonstrate that the Lime Peak platform was surrounded by a basin with an aphotic sea bottom. The carbonate complex developed in warm waters characterized by high carbonate saturation. The area was also defined by moderate to high nutrient levels: this influenced the type of carbonate factory by favouring microbialites and sponges over corals. During its growth, Lime Peak was influenced by tectono-eustatism, which controlled the accommodation space at the platform top, primarily impacting the internal platform environments and the stability of the slope. Gaining better knowledge of the spatial distribution and dynamics of Upper Triassic organisms and sedimentary facies of Panthalassa in relation to tectono-eustatism lays the first foundations for reconstructing more robust platform models and understanding the evolution of other, more dismantled Upper Triassic Panthalassan carbonate systems through time. [ABSTRACT FROM AUTHOR]

The Upper Triassic Xujiahe Formation in the Sichuan Basin is a tight sandstone reservoir with developed dissolution pores, but its formation mechanism is still unclear. In this paper, three samples, including feldspathic lithic, lithic arkose and feldspathic quartz sandstones of the Xujiahe Formation, were taken as examples. Some reaction fluid similar to the organic acid component of the formation was prepared. Five kinds of temperature and pressure conditions were applied in the corrosion simulation experiments, and four understandings were obtained. Firstly, with the increase of temperature and pressure, the concentrations of K+ and Na+ ions in the reaction solution increased, the concentrations of Ca2+ and Mg2+ ions remained stable, but the concentration of Al3+ ions decreased significantly. Secondly, the reaction produced a small amount of quartz and a large number of kaolinite and other new minerals, and the dissolution of feldspar particles and carbonate cement produced a large number of dissolution pores, the porosity was increased and the pore structure was then improved. Thirdly, with the same temperature and pressure, the dissolution rate of feldspathic lithic sandstone was relatively higher than that of feldspathic quartz sandstone. With higher temperature and pressure (e.g. 180℃, 53 MPa), the dissolution rate of sandstone samples were significantly increased. Lastly, the results of dissolution experiments provided a reference for the reconstructing of burial sequence, diagenesis as well as pore evolution of the Xujiahe Formation and the distribution of favorable reservoirs can be predicted. The rapid dissolution of feldspar under higher temperature pressure is one of the genetic mechanisms of effective reservoir of deep clastic rock.

New records enrich the Late Triassic theropod assemblage of the Dockum Group of Texas. Here, five unpublished theropod specimens (TTU-P11175, TTU-P12531X, TTU-P12587X, TTU-P14786, TTU-P16789) are described, each represented by a single element and collected from various fossil localities of Garza County, Texas. Additionally, two previously described specimens (TTU-P10082, TTU-P10534), which were also recovered from Upper Triassic rocks of Garza County are revisited for additional remarks on their anatomy. These new theropod specimens increase the abundance and disparity of theropods in the Dockum terrestrial vertebrate fauna. Together, with confirmed theropod discoveries in other recent works, the newly evaluated specimens add to the long history of dinosaur research in the Dockum Group of Texas.

During the Late Triassic, the southern margin of the Ordos Basin was influenced by the Indosinian Movement, in response to closure of the Paleo-Tethys Ocean. Thinly bedded tuff layers are exposed near the base of the Middle–Upper Triassic formations (Chang 8/7/6 members) in the Ordos Basin. Tuff samples from drilling core (well An-35) and outcrop (Motiangou section) samples in the Yanchang Formation were studied by the detailed field work. Igneous zircon crystals were picked and analyzed by the instruments of cathodoluminescence and laser ablation inductively coupled plasma mass spectrometery (LA-ICP-MS). The timing of volcanic activity was determined by means of high-precision zircon age. Combining tectonic setting and paleogeographic reconstruct, the ages of tuff layers indicate that volcanic activities occurred at three peaks (241.6 ± 1.1 Ma, 240.2 ± 1.1 Ma, and 233.5 ± 1.2 Ma) from the top of Chang 8 Member to the Chang 7 Member. The results implied that the volcanic activities lasted from Ladinian to Carnian, as well as define the sedimentary duration of the Chang 7 Member with a deposition rate of 1.34 cm/ka.

The petrophysical properties of tight reservoirs and the state of fluid occurrence are affected by current geostress. In the past, there were few studies on the rock mechanical properties and in situ stress of the Yanchang Formation in the central and western regions of the Ordos Basin, which restricted the efficient exploration and development of tight oil and gas. A systematic study was carried out on the rock mechanical properties, in situ stress characteristics and their effects on the petrophysical properties of the Chang 6-Chang 8 reservoirs in the Wuqi, Zhidan and Dingbian areas in the Ordos Basin. A reliable method of in situ stress logging interpretation using fracturing methods and logging models was established. The Chang 6 to Chang 8 in Wuqi area is not significantly stressed. The horizontal stress activity deep in the Zhidan area is greater than that in the shallow layers, with the strong horizontal stress intensity mainly concentrated in Chang 73 and Chang 8. The horizontal stress activity of the Dingbian area is relatively strong from Chang 6 to Chang 8, and the horizontal stress intensity of the shallow layer is slightly stronger than that of the deep layer. The stress gradients in the three work areas are determined. The horizontal principal stress gradient gradually increases from northwest to southeast. Finally, the influence of horizontal compression stress on the path of rock compaction and the petrophysical properties of the reservoir are systematically discussed. It was found that the increase of σH-σh did not cause the loss of rock pores alone. The stress plane heterogeneity will cause three different paths of rock porosity changes. However, the increase of the horizontal principal stress difference will mainly cause a decrease of rock permeability.

The study of two stratigraphic sections of the Tran Formation (upper Carnian–Norian) reveals the presence of a regressive carbonate beach succession. The interpretation of lower shoreface, upper shoreface, foreshore, and backshore deposits is based on field data, microfacies analysis and comparison with Holocene and ancient analogues. The various lower shoreface deposits include automicritic boundstones/cementstones which attest to a temporary establishment of the M factory most likely as an aftermath of the global Carnian Pluvial Episode. The upper shoreface grainstones show trough cross-bedding reflecting deposition by longshore currents. Grainstones/packstones of the foreshore subenvironment have several diagnostic features including low-angle plane lamination, keystone voids, eroded beachrock clasts, and well-sorted textures with marine phreatic and vadose cements. Their deposition was controlled by supply of granular material from the shoreface, incessant wave activity and daily tides, and early lithification protecting them from erosion and remobilization. The backshore strata comprise storm washover deposits (packstones, wackestones), mudstones deposited in marginal ponds, and agglutinated stromatolites (formed by trapping and binding in a tide-influenced setting). Some of the foreshore and backshore sediments were pedogenically modified, resulting in the formation of secondary matrix, root development, desiccation cracking, and grainification. Specific products of the early vadose alteration are laminoid fenestrae with crystal silt and diagenetic grainstones, packstones, and wackestones. The good preservation of the regressive beach succession was favored by late highstand progradation of the shoreline in a low accommodation setting. [ABSTRACT FROM AUTHOR]

Relics of the Panthalassa Ocean occur today in accretionary complexes and terranes on the entire Circum‐Pacific region. Among them, remains of shallow‐water carbonate systems provide valuable information about the ecology and environmental conditions that prevailed in this immense ocean. In this regard, the Shiriya Cape of the North Kitakami Belt (Aomori Prefecture, Honshu Island, Japan) is an essential place to study. Characterized by the presence of numerous limestone deposits embedded in typical accretionary mélange, including pluri‐kilometric massive slabs and metric bedded deposits, the cape is indeed a key vestige of carbonate deposition in the Panthalassa. All the limestone outcrop form the Shiriya Cape were sampled and studied in detail for the first time. Despite a general poor preservation, macroscopic sedimentary features such as burrows and large megalodontids patches as well as four microfacies were identified and are presented in detail in this work. On the basis of foraminifers and conodonts biostratigraphy, the age of the limestone deposits is defined as Norian. Similarities with analogous and synchronous systems from Panthalassan and Tethyan realms are extensively discussed. The closest analog to the Shiriya limestone appears to be the Panthalassan Dalnegorsk limestone (Russian Far East), both regarding microfacies and depositional setting. Sedimentary successions similar to Lofer‐cycles, well known in Tethyan synchronous systems, were also discovered in the Shiriya Cape. Along with the large limestone slabs, countless limestone‐bearing conglomerates also crop out on the Shiriya Cape. Their study and comparison with similar deposits in Japan highlighted their importance in the understanding of the dismantling of mid‐oceanic carbonates. The observations and comparison with well‐known carbonate systems permitted to establish a hypothetical depositional model of the Shiriya limestone corresponding to a Norian isolated carbonate system developed on an immerged volcanic seamount. [ABSTRACT FROM AUTHOR]

Introduction The investigated area in northeastern Iran that is known as the Tarik Darreh arsenopyrite-Au-W prospecting target is situated in the Kopeh Dagh zone (Fig. 1). Most of the study area is covered with black slate rocks which most authors have referred to as Upper Triassic with Norian age (e.g., Behroozi et al., 1993). Plutonic rocks with gabbro, diorite, and quartz diorite and monzodiorite composition were introduced in the slate rocks. The previous studies in the Tarik Darreh are the preliminary report of arsenopyrite with Au-W quartz lode mineralization carried out by Taghizadeh (1965). Since then, the Geological Survey of Iran (e.g., Alavi Naini and Mossavi-Khorzughi, 2006) a few geologic companies and the universities (Shafi Niya, 2002) and Ghavi et al. (2013) have been studying in the area. In the present study, we provide more information, complete with new information about the geology of the Tarik Darreh area. Materials and methods Expansive field geology surveying to draw a geology map in 1:8000 scale and sampling from plutonic rocks was performed and two main fault system were distinguished in Tarik Darreh (Figs. 2 and 3). Thin section microscopic studies were carried out following field investigations. Magnetic susceptibility was measured with a portable Model KT-10 and GMS-2 Fugro instrument (precision of 0.0001 SI units). Sixteen samples of intrusive bodies and dykes were analyzed for major and trace elements using 4E-Reserch package (INAA, FUS ICP-OMS, ICP-MS) at the Acme Lab (Canada). Gabbroic units were selected for U-Pb geochronological study. In the heavy liquid process, zircon crystals were separated, hand-picked under microscope. Zircon grains for Th-U-Pb dating were examined by an Agilent 7700 quadrupole ICPMS at the University of Tasmania (Australia). Discussion and Results Plutonic rocks in the Tarik Darreh area are in the form of bodies and dykes. The plutonic bodies are mostly gabbro, gabbro diorite, diorite (hornblende pyroxene diorite, biotite hornblende diorite and hornblende biotite diorite), biotite hornblende monzodiorite, quartz diorite, and quartz monzonite in composition. However, it is diorite with granular textures as a common rock (Figs. 4 and 6). Other rocks as dyke have more hornblende diorite composition with porphyritic textures. Common mafic minerals in the plutonic rocks in the Tarik Darreh include pyroxene, hornblende and biotite. The alteration assemblages of uralite, chlorite, calcite and sericite are very common gabbroic-diorite rocks (Fig. 5). The plutonic rocks have SiO2 with values in the range of 46 to 56% (Table 1). Therefore, these rocks are intermediate in composition. Most of these rocks also have high K-calc-alkaline composition with metaluminous characteristic (Fig. 7). Enrichment in LREE relative to HREE, low La/By ratio, enrichment in LILE and negative anomaly of Eu, Ti, Zr, Y and Ba are shared in all of the studied plutonic rocks and dykes (Figs. 8 and 9). All the plutonic rocks have low values of magnetic susceptibility (less than 3×10-3 SI). Two main systems of fault have affected the area (Fig. 10). Plutonic rocks from the Tarik Darreh area are placed within the volcanic arc to within plate’s environment in tectonic setting discrimination diagrams (Fig. 11). Zircon U-Pb dating results on the gabbroic rocks are shown in Table 2. Zircon grains through cathodoluminescence imaging show euhedral, clear crystals with no visible heritage cores. However, some of them have inclusions. Zircon U-Pb dating indicates that the gabbroic rocks formed at 215.5±0.9 Ma (late Triassic) (Fig. 12). Thus, it is obvious that the country rock (called Miankuhi Formation), must be older than the late Triassic plutonic rocks rather than Norian age as previously thought. The variation of major elements with SiO2 in the plutonic rocks from Tarik Darreh (Fig. 13) indicates that the primary magma of these plutonic rocks underwent fractional crystallization from gabbro to quartz monzodiorite. Geochemical characteristics such as low ratios of (La/Yb)N (

The diagenesis and pore evolution process of tight sandstone reservoirs in the Upper Triassic Bagong Formation of the North Qiangtang Depression were studied by means of physical properties, casting thin slice, SEM, X-ray-diffraction and fluid inclusion temperature measurement. The compositional maturity and structural maturity of the Bagong sandstones are moderately low. Their physical properties are extremely tight. The main diagenetic effects include compaction, cementation, dissolution and metasomatism. The cement components are mainly siliceous, clay minerals and carbonate minerals, and the dissolution component is feldspar. According to the comprehensive analysis of various characteristics, the shallow buried area near the uplift is in the middle diagenesis stage B, and the deep buried area inside the depression is in the late diagenetic stage. Under the premise of considering the apparent volume change and compaction of rock, a quantitative calculation of pore evolution of different diagenetic facies is carried out. The calculation results show that compaction is the primary cause of reservoir porosity reduction, followed by cementation, while dissolution and the formation of chlorite lining are beneficial to reservoir porosity.

The Bled Basin was a Middle Triassic–Early Cretaceous basin whose remnants are preserved in the eastern Southern Alps in western Slovenia. The early evolution of the basin is recorded in the Upper Ladinian to Lower Jurassic Zatrnik cherty limestone formation, which in the Pokljuka Nappe overlies Middle Triassic volcanics, volcaniclastics and hemipelagic limestones. The Zatrnik Limestone is poorly documented and biostratigraphically not well constrained. The base of the Zatrnik Limestone was logged in four sections in the eastern part of the Pokljuka plateau. An Upper Ladinian Muelleritortis cochleata Radiolarian Zone was recognised in the lowermost part, whereas conodont data indicate Julian to latest Tuvalian/early Norian age for the rest of the logged sections. Microfacies analysis indicates hemipelagic deposition on a basin plain and/or distal slope, which is often interrupted by distal calciturbidites.

The North Dobrogean Orogen (NDO) is a NW-SE trending fold-and-thrust belt in the eastern foreland of the Alpine Carpathian Orogen, palaeogeographically representing the westernmost segment of the Palaeotethys-issued Cimmeride Orogenic System. Eastwards, the NDO structurally extends into the Romanian sector of the western Black Sea continental shelf. The Triassic development of North Dobrogea is well known for its Tethyantype facies and richness in various groups of fossils, but little attention has been paid to microfacies and fossil content of the offshore Triassic. The drill hole 817 LV of the Lebăda Vest oilfield, offshore Romania, ends in the Rhaetian (Upper Triassic) limestone olistolith, from which a rich association of foraminifers and ostracods was recovered. The limestone also contains sponge spicules, mollusc fragments, echinoderm ossicles, bryozoans, and brachiopods. Foraminiferal assemblage from the residue consists of agglutinated species only. Tolypamminids, Gaudryinopsis triadica (Kristan-Tollmann), G. triassica (Trifonova), G. kelleri (Tappan), Ammobaculites tzankovi (Trifonova), A. zlambachensis Kristan-Tollmann, Verneuilinoides racema (Trifonova), and Trochammina spp. predominate. Non-agglutinated species, determined from thin sections include Ophthalmidium spp., and rare involutinids Trocholina ex gr. intermedia/umbo and "Involutina turgida" (Involutina ex gr. liassica). The rich ostracod assemblage is dominated by Bairdiidae. Species of the Paracyprididae and Sigilliidae families are rather common. The conodont Norigondolella steinbergensis (Mosher) was also found. The deposition is suggested to take place in a relatively deep setting (outer shelf) offshore heterozoandominated platform in relatively cool waters. [ABSTRACT FROM AUTHOR]

In geological history, volcanism is closely related to the deposition of many black shales. However, the specific mechanism between volcanism and the deposition of black shales is still unclear. The black shales developed in the Chang 7 Member of the Yanchang Formation in the Ordos Basin are considered the most important hydrocarbon source rocks in Central China. The shales are deposited by frequent volcanic activities and preserved by extremely rich volcanic ash layers, making them an excellent example when investigating the influence of volcanism on the deposition of black shales. In this paper, petrographic, mineralogical, and geochemical analyses of three typical tuff and black shale segments of the Chang 7 Member were carried out. The productivity indicators [total organic carbon (TOC), P/Al, Ni/Al, and Cu/Al], redox indicators (V/Al, Mo/Al, U/Al and U/Th), and clastic influx indicators (Ti/Al and ƩREE) of the shales basically increased together in the longitudinal direction, and a relatively good positive correlation existed between P/Al, Ni/Al, Cu/Al, V/Al, Mo/Al, U/Al, U/Th, Ti/Al, ƩREE, and TOC. This finding indicated that the development of the Chang 7 black shales is the result of a combination of high primary productivity, anoxic conditions, and increased clastic influx. Considering that increased clastic influx may dilute organic matter, many phosphate nodules represented high productivity above the volcanic ash layers, and anoxic conditions are likely to be the result of a large amount of organic matter degradation indicated by the covariations of TOC versus P/Al and TOC versus Ba/Al. Therefore, the Chang 7 black shales in this study may be mainly controlled by the increased primary productivity. In addition, compared with the Weathering Index of Parker of background shales (not the contact clip or tuff layer), that of the black shales was significantly reduced after tuff deposition. On the contrary, the clastic influx indicators, redox indicators, productivity indicators of black shales significantly increased. This finding suggested that a series of environmental effects, such as enhanced weathering of terrestrial sources, increased clastic influx, anoxic water, and productivity bloom, was likely caused by volcanic activity. Considering that hydrothermal activity at the same time as volcanism may not cause productivity bloom, the nutrients (P/Al and Fe/Al) of the Chang 7 tuffs were significantly depleted, and the total sulfur content of black shales was much higher than that in ordinary freshwater sedimentation. Therefore, this paper reviewed and proposed the volcanism hypothesis model of the Chang 7 black shales. Volcanism generates large amounts of SO2 and volcanic ash. SO2 forms large areas of acid rain and accelerates terrigenous weathering with an increase in the lake land-based sources of debris and nutrient supply, while volcanic ash is decomposed and releases nutrients. These phenomena lead to biological productivity bloom and massive accumulation of organic matter, which in turn results in lake water anoxia and the eventual formation of black shales. [ABSTRACT FROM AUTHOR]

The North Dobrogean Orogen (NDO) is a NW-SE trending fold-and-thrust belt in the eastern foreland of the Alpine Carpathian Orogen, palaeogeographically representing the westernmost segment of the Palaeotethys-issued Cimmeride Orogenic System. Eastwards, the NDO structurally extends into the Romanian sector of the western Black Sea continental shelf. The Triassic development of North Dobrogea is well known for its Tethyan-type facies and richness in various groups of fossils, but little attention has been paid to microfacies and fossil content of the offshore Triassic. The drill hole 817 LV of the Lebăda Vest oilfield, offshore Romania, ends in the Rhaetian (Upper Triassic) limestone olistolith, from which a rich association of foraminifers and ostracods was recovered. The limestone also contains sponge spicules, mollusc fragments, echinoderm ossicles, bryozoans, and brachiopods. Foraminiferal assemblage from the residue consists of agglutinated species only. Tolypamminids, Gaudryinopsis triadica (Kristan-Tollmann), G. triassica (Trifonova), G. kelleri (Tappan), Ammobaculites tzankovi (Trifonova), A. zlambachensis Kristan-Tollmann, Verneuilinoides racema (Trifonova), and Trochammina spp. predominate. Non-agglutinated species, determined from thin sections include Ophthalmidium spp., and rare involutinids Trocholina ex gr. intermedia/umbo and “Involutina turgida” (Involutina ex gr. liassica). The rich ostracod assemblage is dominated by Bairdiidae. Species of the Paracyprididae and Sigilliidae families are rather common. The conodont Norigondolella steinbergensis (Mosher) was also found. The deposition is suggested to take place in a relatively deep setting (outer shelf) offshore heterozoan-dominated platform in relatively cool waters.