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This paper reports on geochronological U–Pb studies of baddeleyite from nepheline syenite of the Korgere-Daba alkaline massif, which is the largest massif within the Sangilen Highlands (Tyva). The established age of rocks, 295 ± 1 Ma, indicates that, in the Early Permian, undersaturation by silica magmatism occurred in the region in addition to the alkaline-granite magmatism (Ulug-Tanzek, etc.). This age furthermore points to the need to make corrections in the conceptions of a petrophysical type for the Devonian Sangilen complex, which is traditionally distinguished in this region. Until now, the Korgere-Daba massif has been considered in this regard. [ABSTRACT FROM AUTHOR]

Sodium carbonate evaporites can provide important paleoclimatic constraints and economic resources but are relatively rare; most known examples are limited to the Cenozoic. The first known late Paleozoic occurrence was recently reported from the Fengcheng Formation in the northwestern Junggar Basin, NW China. However, its mineralogy, age, and geologic setting have been sparsely documented. To help establish a broader understanding of the formation of these important deposits, this paper presents a comprehensive new data set that includes drill core, well logs, petrographic analyses, X-ray diffraction data, organic geochemistry (biomarkers), and U-Pb zircon age data. Evaporite deposition is estimated to have occurred between ca. 305 Ma and 296 Ma in a series of extensional grabens that hosted a stratified, hypersaline lake (or lakes). The lake deposits are closely associated with coeval volcanic rocks, suggesting that subsurface interaction of these with CO2-enriched hydrothermal fluids may have contributed to the excess alkalinity required to precipitate Na-carbonate. Trona (NaHCO3 · Na2CO3 · 2H2O) in the Fengcheng Formation was likely formed syndepositionally and then partly replaced by wegscheiderite (Na2CO3 · 3NaHCO3). Other evaporite minerals most likely formed during diagenesis. The Fengcheng Formation also contains nahcolite (NaHCO3), which requires pCO2 >680 ppm to form, although no textural evidence was found to demonstrate a primary origin. The presence of extensive lacustrine evaporites nonetheless reflects a relatively warm and arid climate at ~40-50°N that apparently coincided with the late Paleozoic icehouse. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Tarim Craton experienced both active and passive rifting during the Cryogenian. • The rift system shows a two-tiered architecture with narrow-deep Cryogenian grabens overlain by a broad Ediacaran depression. • Both active and passive rifting are thought to have been triggered by retreating subduction in the late Neoproterozoic. The Cryogenian-early Paleozoic succession in the Tarim Craton is generally regarded as a continuous rift sequence that followed the prolonged superplume-related breakup of Rodinia. However, the rift architecture and origin of the late Neoproterozoic basin are poorly known, but these are important for the understanding of the tectonic evolution of the basin and for the evaluation of the hydrocarbon potential. This paper aims to elucidate the rift architecture, distribution, origin and evolution of the late Neoproterozoic Tarim Basin by integrating outcrop investigations with well and seismic data. The late Neoproterozoic magma-rich active rifting primarily occurred in the northeastern part of the basin, whereas other areas experienced slightly younger magma-poor passive rifting. The Ediacaran succession overlaps in the northern basement uplift to show a pre-Ediacaran unconformity occurs in the northern Tarim Craton, while a sub-Cambrian unconformity traverses the entire Tarim Craton and presents a distinct truncation in the southern basement uplift. A tiered architecture exists in which narrow, deep Cryogenian grabens are overlain by a broad Ediacaran depression. Two NE-striking rift systems developed in the northeastern and southwestern Tarim. It can be inferred from the compiled data that the late Neoproterozoic rift basin evolution in the Tarim Craton can be divided into four stages: early Cryogenian rifting, late Cryogenian fault-graben, Ediacaran intracratonic depression, and end-Ediacaran regional uplifting. These results suggest that documented Neoproterozoic retreating subduction-related slab failure/detachment processes led to both active and passive rifting, which contributed to the diverse continental rift architecture and evolution of the late Neoproterozoic Tarim Basin. [ABSTRACT FROM AUTHOR]

It is beneficial in terms of the theoretical significance and application prospects to define the structure and reservoir development model of the lower Paleozoic unconformity in the Jiyang Depression of Bohai Bay Basin, China, for oil and gas exploration of unconformity in carbonate strata. Geological and geochemical evidence shows that a regional unconformity formed during the Huaiyuan Movement in the lower Paleozoic strata of the Jiyang Depression. Along the top of the regional unconformity between the Yeli Liangjiashan Formation and Fengshan Formation, various types of karst breccia have developed, showing prominent characteristics of development and vertical karst zonation. The paleokarst zone can be divided into the vadose zone and the underflow zone, and there are apparent differences between the two zones in terms of the mode of karst activity and type of reservoir space. Primitive sedimentary microfacies, dolomitization, and supergene karstification controlled the reservoirs of the Fengshan Formation and Yeli-Liangjiashan Formation. There are significant differences in the original physical properties due to the differences in the original sedimentary microfacies. The pore development of granular dolomite of high-energy beach facies has the best reservoir performance. In the later period, the superposition of dolomitization and supergene karstification resulted in apparent differences in karst development mode, development intensity, reservoir type, and reservoir physical properties. Among them, the granular dolomite reservoir has the best physical properties and has developed a cavity-type reservoir that has a planar distribution along an unconformity surface. [ABSTRACT FROM AUTHOR]

The phase of secular evolution of continents is manifested as the degree of compositional differentiation, modification and maturation of continental crusts, which is vital in understanding the mechanism of continental evolution but is difficult to quantify. Here we use integrated passive- and active-source seismic profiling to conduct joint analysis and inversion and derive Vs and Vp/Vs section models across the North China Craton (NCC) to southeastern Altaids boundary zone that bears a tectonic transition from a reworked ancient craton margin to a Phanerozoic accretionary orogen. We systematically exploited the imaged multiple physical properties as precise and delicate proxies to constrain the compositional architecture in the crust across this important tectonic transition subject to various crustal evolutional phases. Our Vs and Vp/Vs imaging, together with the existing isotopic data, characterizes the Yin Shan–Yan Shan belt as the northern NCC margin with layered homogeneous compositions that point to an evolved crust. However, the lower-crustal low-Vs/high-Vp/Vs signature that overlaps the shallowly dipping to horizontal reflective fabrics suggests that the crust of the northern NCC margin has undergone considerable reworking through lower-crustal-stretching-assisted melt migration and mixing since the late Paleozoic to Mesozoic eras. The process probably involved crust–mantle interaction and thus resulted in a compositionally modified ancient crustal basement. On the contrary, the southeastern Altaids domain manifests crustal complexity in compositions and structures inferred to be indicative of a juvenile crust of the Phanerozoic accretionary orogen. Our results provide deep physical-property constraints that shed new light on the crustal evolution of a complex craton margin. [ABSTRACT FROM AUTHOR]

Alkalic magmatism occurred in the Selwyn Basin, Yukon, Canada throughout the Paleozoic, concurrent with extension during passive margin sedimentation. To examine magmatism associated with this extension, geochemical data were obtained from several locations in the Selwyn Basin (MacMillan Pass, Anvil District, Keno Hill, and the Misty Creek Embayment). Volcanic rocks from the Anvil District and the Misty Creek Embayment are dominated by alkalic basalts with light rare earth element (LREE)-enriched geochemical signatures, whereas metavolcanic and dike samples from Keno Hill comprise subalkaline basalts with enriched mid-ocean ridge basalt (E-MORB) signatures. The Early Ordovician Menzie Creek volcanic rocks of the Anvil District display trace element geochemical signatures intermediate between ocean island basalt (OIB) and E-MORB, whereas the Middle–Late Ordovician volcanic rocks from the Misty Creek Embayment have OIB signatures. Differences in the trace element geochemistry of the sample suites are attributed to the degree of partial melting. The Menzie Creek volcanic rocks formed from large volume melts of enriched mantle that diluted incompatible element signatures in the Early Ordovician. Late Ordovician magmatism produced the Misty Creek Embayment samples, where restricted melt volumes of an enriched mantle source resulted in the most enriched samples geochemically. The Keno Hill samples represent the shallowest melting of the analysed samples and may have resulted from melting of heterogenous subcontinental lithospheric mantle. Magmatic zircons from a Keno Hill metavolcanic sample analysed by chemical abrasion thermal ionization mass spectrometry resulted in a primary deposition age of c. 296 ± 0.36 Ma (Early Permian), during a period with little magmatism in the Selwyn Basin and representing a previously unknown unit in the area. [ABSTRACT FROM AUTHOR]

The geologic history of the Western Tianshan region is important for understanding the evolution of the Central Asian Orogenic Belt and accretionary orogenesis. Paleozoic and Mesozoic igneous rocks are present along the northern margin of the Yili Block; however, studies of Paleozoic subduction and collisional events have been relatively limited. Published geochronologies of Middle Devonian magmatic rocks in this region are also lacking. Therefore, this study analyzed the zircon U–Pb ages and major and trace elemental compositions of three granite types collected from Biezhentao Mountain (Wenquan County, Western Tianshan). The medium-grained diorite (384.1 ± 3.6 Ma) and diorite–porphyrite (382 ± 3.2 Ma) are silica-rich, weakly peraluminous, alkali-rich, enriched in large-ion lithophile elements, depleted in high field strength elements, and belong to the calc–alkaline series, with A-type granite characteristics. The monzogranite (423.3 ± 9.4 Ma) exhibits A-type granite characteristics and belongs to the peraluminous calc–alkaline series. The findings suggest that the granitoids recorded two stages of tectonomagmatism during the Middle Devonian–Late Silurian. The Middle Devonian medium-grained diorite and diorite–porphyrite formed in a back-arc extensional setting, whereas the Late Silurian monzogranite formed in an active continental margin setting during the subduction of the North Tianshan Ocean. These results provide insights into the tectonic and magmatic processes that occurred during the evolution of the Western Tianshan region and the formation and evolution of the Central Asian Orogenic Belt. [ABSTRACT FROM AUTHOR]

A comprehensive assessment of the critical elements contained in coal is essential for understanding the geological processes that affect the enrichment of these elements, which can then be used to fully utilize coal in an economically and environmentally friendly manner. In order to understand the geology of an area and the impact of demolition rock on the formation and enrichment of trace elements, as well as rare earth elements (REE) in coals, we have presented a range of recent geochemical and mineralogical data from the k7 coal seam in the Karaganda Formation of the Karaganda Coal Basin. The study revealed that the geochemical characteristics of coal-bearing deposits in the Karaganda Basin reflect the features of its geological evolution. Despite high tectonic activity and volcanic activity in the Paleozoic era, the specific composition of the rocks on the slopes and bases of coal-bearing valleys has determined the low potential for rare metals in the basin. It has been found that the coal in the Karaganda Basin is, in general, similar in terms of concentrations of most trace elements to the average for world coal. The main area of provenance of the trace elements was established using discriminant diagrams. It was established that the main source of the trace elements, including REEs in the basin coals, was the Tekturmas accretionary complex that represented the main upland (anticlinorium) during the coals' formation. SEM studies identified micro-mineral forms that indicated the presence of trace elements of Zr, Ti, Se, and Fe in the samples of stratum k7. [ABSTRACT FROM AUTHOR]

The modern relief of Southern Africa is characterised by stepped plateaus bordered by escarpments. This morphology is thought to result from stepwise uplift and ensuing continental-scale erosion of the region as it rode over Africa's mantle 'superplume' following the break-up of Gondwana, i.e. since the mid-Mesozoic. We demonstrate in this contribution that this modern morphology of Southern Africa is in fact largely inherited from glacial erosion associated to the Late Paleozoic Ice Age (LPIA) that occurred between 370 and 260 Myr ago, during which Gondwana – which included Southern Africa – was covered in thick ice masses. Southern Africa hosts vast (up to 106 km²) and thick (up to 5 km) sedimentary basins ranging from the Carboniferous, represented by glaciogenic sediments tied to the LPIA, to the Jurassic-Cretaceous. These basins are separated by intervening regions largely underlain by Archean to Paleoproterozoic cratonic areas that correspond to paleohighlands that preserve much of the morphology that existed when sedimentary basins formed, and particularly glacial landforms. In this contribution, we review published field and remote data and provide new large-scale interpretation of the geomorphology of these paleohighlands of Southern Africa. Our foremost finding is that over Southern Africa, vast surfaces, tens to hundreds of thousands km² (71.000–360.000 km²) are exhumed glacial landscapes tied to the LPIA. These glacial landscapes manifest in the form of cm-scale striated pavements, m-scale fields of roches moutonnées , whalebacks and crag-and-tails, narrow gorges cut into high-standing mountain ranges, and km-scale planation surfaces and large U-shaped valleys, overdeepenings, fjords and troughs up to 200 km in length. Many modern savannahs and desertic landscapes of Southern Africa are therefore relict glacial landscapes and relief ca. 300 Myr old. These exhumed glacial relief moreover exerts a strong control on the modern-day aspect of the geomorphology of Southern Africa as (1) some escarpments that delineate high-standing plateaux from valleys and coastal plains are inherited glacial relief in which glacial valleys are carved, (2) some hill or mountain ranges already existed by LPIA times and were likely modelled by glacial erosion, and (3) the drainage network of many of the main rivers of Southern Africa is funnelled through ancient glacial valleys. This remarkable preservation allowed us to reconstruct the paleogeography of Southern Africa in the aftermath of the LPIA, consisting of highlands over which ice masses nucleated and from which they flowed through the escarpments and toward lowlands that now correspond to sedimentary basins. Our findings therefore indicate that glacial landforms and relief of continental-scale can survive over tens to hundreds of million years. This preservation and modern exposure of the glacial paleolandscapes were achieved through burial under piles of Karoo sediments and lavas over ca. 120 to 170 million years and a subsequent exhumation since the middle Mesozoic owing to the uplift of Southern Africa. Owing to strong erodibility contrasts between resistant Precambrian bedrock and softer sedimentary infill, the glacial landscapes have been exhumed and rejuvenated. We therefore emphasise the need of considering the legacy of glacial erosion processes and the resulting presence of glacial landscapes when assessing the post-Gondwana-breakup evolution of Southern African topography and its resulting modern-day aspect, as well as inferences about climate changes and tectonic processes. Finally, we explore the potential pre-LPIA origin for some of the landscapes. In the Kaoko region of northern Namibia, the escarpments into which glacial valleys are carved may correspond to a reminiscence of the Kaoko Pan-African Belt, whose crustal structures were either reactivated or where relief persisted since then. In South Africa, the escarpment bordering the paleohighland corresponds to crustal-scale faults that might have been reactivated during LPIA by subsidence processes. These inherited morphological or crustal features may have been re-exploited and enhanced by glacial erosion during the LPIA, as it is the case for some Quaternary glacial morphology. [ABSTRACT FROM AUTHOR]

The article presents abstracts of the papers presented in the workshop hosted by conveners Christoph Breitkreuz and Uwe Kroner on topics including cinovec granite cupola, late paleozoic volcanic centers in Central Europe and exhumation channel of the Erzgebirge, Germany.

Copyright of Brazilian Journal of Geology is the property of Sociedade Brasileira de Geologia 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.)

Chert and silicified wood from the Permian through Cretaceous of Antarctica contain abundant information on fungal diversity and plant–fungal interactions. The chert deposits represent a particularly interesting setting for the study of plant–fungal interactions because they preserve remains of distinctive high latitude forest ecosystems with polar light regimes that underwent a profound climate change from icehouse to greenhouse conditions. Moreover, some of the cherts and wood show the predominance of extinct groups of seed plants (e.g. Glossopteridales, Corystospermales). Over the past 30 years, documentation of fossil fungi from Antarctica has shifted from a by-product of plant descriptive studies to a focused research effort. This paper critically reviews the published record of fungi and fungal associations and interactions in the late Palaeozoic and Mesozoic cherts and silicified wood from Antarctica; certain fungal palynomorphs and fungal remains associated with adpression fossils and cuticles are also considered. Evidence of mutualistic (mycorrhizal), parasitic and saprotrophic fungi associated with plant roots, stems, leaves and reproductive organs is presented, together with fungi occurring within the peat matrix and animal–fungus interactions. Special attention is paid to the morphology of the fungi, their systematic position and features that can be used to infer fungal nutritional modes. [ABSTRACT FROM AUTHOR]

Famennian tabulate corals were very rare worldwide, and their biodiversity was relatively low. Here we report a unique tabulate fauna from the mid- and late Famennian of the western part of the Holy Cross Mountains (Kowala and Ostrówka), Poland. We describe eight species (four of them new, namely ?Michelinia vinni sp. nov., Thamnoptychia mistiaeni sp. nov., Syringopora kowalensis sp. nov. and Syringopora hilarowiczi sp. nov.); the whole fauna consists of ten species (two others described in previous papers). These corals form two assemblages—the lower, mid-Famennian with Thamnoptychia and the upper, late Famennian with representatives of genera ?Michelinia, Favosites, Syringopora and ?Yavorskia. The Famennian tabulates from Kowala represent the richest Famennian assemblage appearing after the F/F crisis (these faunas appear some 10 Ma after the extinction event). Corals described here most probably inhabited deeper water settings, near the limit between euphotic and disphotic zones or slightly above. At generic level, these faunas show similarities to other Devonian and Carboniferous faunas, which might suggest their ancestry to at least several Carboniferous lineages. Tabulate faunas described here represent new recruits (the basin of the Holy Cross mountains was not a refuge during the F/F crisis) and have no direct evolutionary linkage to Frasnian faunas from Kowala. The colonization of the seafloor took place in two separate steps: first was monospecific assemblage of Thamnoptychia, and later came the diversified Favosites-Syringopora-Michelinia fauna. [ABSTRACT FROM AUTHOR]

The nature of source rocks and the pressure-temperature-hydration (P-T-H2O) condition are the two main factors that control the geochemical properties of granites. Therefore, the evolution of P-T-H2O conditions can be used to deduce the tectonic setting of granites. In this paper, we report on three Paleozoic granite plutons along the Shangdan suture that revealed increasing melting temperature and decreasing pressure from 437 to 403 Ma, suggesting a crustal thinning process. The Tieyupu granodiorites (437 ± 4 Ma) display Na-rich adakite affinity, i.e., SiO2 = 69.1-70.1 wt%, Na2O/K2O = 1.9-2.26, positive zircon εHf(t) values (+4.29 to +12.04), and high Sr/Y (137-160) and Y/Yb (9.89-10.25) ratios, implying a garnet-rich residue in their source. In combination with moderate zircon saturation temperatures (814-822 °C), we infer that the Tieyupu granodiorites were formed by melting of Neoproterozoic metabasites under high-pressure (>1.5 GPa) and moderate-temperature (HP-MT) conditions. The Liangchahe granodiorites (415 ± 8 Ma) also display Na-rich adakite affinity, i.e., higher Na2O/K2O (2.16-3.11) and lower Sr/Y (77-88) ratios, and higher zircon saturation temperatures (854-874 °C), and they are interpreted to have been derived from melting of metabasites under moderate-pressure (>1.0 GPa) and high-temperature (MP-HT) conditions. Their variable zircon εHf(t) values (-14.97 to +9.80) and the existence of zircon xenocrysts suggest that the primitive adakitic melts were assimilated by evolved crustal components. The Yaogou monzogranites (403 ± 4 Ma) have the highest K2O/Na2O (0.81-1.00) ratios and total rare earth element (ΣREE; 105-191 ppm) contents, lowest Sr/Y (14-43) ratios, positive zircon εHf(t) values (+6.79 to +12.22), and highest zircon saturation temperatures (891-973 °C), showing they were formed by high-temperature melting of intermediate rocks under low-pressure conditions (<1.0 GPa). The evolution of P-T conditions revealed by these three granites suggests that crustal growth and differentiation were related to gradual extensional and melting of mafic protoliths in the orogenic belt. [ABSTRACT FROM AUTHOR]

This paper reports the first data on present-day movements in the northern margin of the Argun Continental Massif, obtained on the basis of GPS measurements. The processed GPS data have been obtained to calculate the vector field of displacement velocities in the geodynamic survey site of the Upper Amur Region. The estimated displacement parameters (direction and magnitude) are indicative of the uniform velocity vector field of the points in the northern margin of the Argun Massif and the absence of considerable motions within its range (differences in the vector components do not exceed a few millimeters per year). A conclusion is made on the present-day kinematic integrity of the northern margin of the Argun Massif. [ABSTRACT FROM AUTHOR]

Copyright of Review of the Bulgarian Geological Society is the property of Bulgarian Geological Society 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.)

Great progress has been made in middle Permian exploration in Northwest Sichuan in recent years, but there are still many questions in understanding the hydrocarbon accumulation conditions. Due to the abundance of source rocks and the multi-term tectonic movements in this area, the hydrocarbon accumulation model is relatively complex, which has become the main problem to be solved urgently in oil and gas exploration. Based on the different tectonic backgrounds of the middle Permian in northwest Sichuan Basin, the thrust nappe belt, the hidden front belt, and the depression belt are taken as the research units to comb and compare the geologic conditions of the middle Permian reservoir. The evaluation of source rocks and the comparison of hydrocarbon sources suggest that the middle Permian hydrocarbon mainly comes from the bottom of the lower Cambrian and middle Permian, and the foreland orogeny promoted the thermal evolution of Paleozoic source rocks in northwest Sichuan to high maturity and over maturity stage. Based on a large number of reservoir physical properties data, the middle Permian reservoir has the characteristics of low porosity and low permeability, among which the thrust nappe belt and the hidden front belt have relatively high porosity and relatively developed fractures. The thick mudstone of Longtan formation constitutes the regional caprock in the study area and the preservation condition is good as a whole. However, the thrusting faults destroyed the sealing ability of the caprock in the nappe thrust belt. Typical reservoir profiles revealed that the trap types were different in the study area. The thrust fault traps are mainly developed in the thrust nappe belt, while the fault anticline traps are developed in the hidden front belt, and the structural lithological traps are developed in the depression belt. The different structural belts in northwest Sichuan have different oil and gas accumulation models. This paper built three hydrocarbon accumulation models by the analysis of reservoir formation conditions. The comprehensive analysis supposed the hidden front belt is close to the lower Cambrian source rock, and the reservoir heterogeneity is weak, faults connected source rock is developed, so it is a favorable oil and gas accumulation area in the middle Permian. [ABSTRACT FROM AUTHOR]

Predation as an evolutionary mechanism of diversification is a topic of great interest. Durophagy is the feeding behavior of preying on hard-shelled or exoskeleton-bearing organisms. On this matter, because of their worldwide distribution, abundance, wide range of habitats, and a remarkable preservation frequency, mollusks are of particular interest in the study of predation in the fossil record. In the present work, papers published in international scientific magazines focusing on the issue of durophagy on fossil marine bivalve and gastropods as potential prey were analyzed. A total of 101 papers on this subject were reviewed. Six-kinds of evidence of durophagy were identified: drilling, repaired and fragmented shells, bites, punctures and coprolites. Most items are of Cenozoic age and the majority of the records available correspond to the tropics. Most Paleozoic potential predators were not identified; this situation extends to the Mesozoic, but predation of gastropods and bivalves by carnivorous gastropods, arthropods, fishes and reptiles was recognized. Predation by naticid and muricid gastropods prevails during the Cenozoic, also was recognized predation by arthropods, fishes and mammals. [ABSTRACT FROM AUTHOR]

The South China Block was formed through the collisional orogeny between the Cathaysia Block and the Yangtze Block in the Early Neoproterozoic. The northern, western and southern sides of the South China Block were affected by disappearance of the Paleo-Tethyan Ocean during the Paleozoic. The southern and northern sides of the South China Block were respectively collided with the Indo-China Block and North China Block in the latest Paleozoic to form the basic framework of the Eastern China. The Eastern China has been affected by the westward subduction of the Pacific Plate since the Mesozoic. Therefore, the South China Block was influenced by the three major tectonic systems, leading to a superposed compound tectonics. The comparative study of the Mesozoic geology between the South China Block and its surrounding areas suggests that although the Mesozoic South China Block was adjacent to the subduction zone of the western Pacific, no juvenile arc-type crust has been found in the eastern margin. The main Mesozoic geology in South China is characterized by reworking of ancient continental margins to intracontinental tectonics, lacking oceanic arc basalts and continental arc andesites. Therefore, a key to understanding of the Mesozoic geology in South China is to determine the temporal-spatial distribution and tectonic evolution of Mesozoic magmatic rocks in this region. This paper presents a review on the tectonic evolution of the South China Block through summarizing the magmatic rock records from the compressional to extensional tectonic process with the transition at the three juncture zones and using the deformation and geophysic data from the deep part of the South China continental lithosphere. Our attempt is to promote the study of South China's geology and to make it as a typical target for development of plate tectonic theory. [ABSTRACT FROM AUTHOR]

Reconstruction of proportions between juvenile and recycled crust remains challengeable because a big part of juvenile source magmatic rocks formed at intra-oceanic arcs, can be destroyed by surface and tectonic erosion leaving, at best, greywacke sandstones. Such sandstones are typically hosted by accretionary complexes, which study, therefore, is of crucial importance. In this paper we review available geological and micropaleontological data and present first U Pb detrital zircon ages, geochemical data and isotope (Sm Nd, Lu Hf) data from sandstones of the late Cambrian-early Ordovician Zasur'ya accretionary complex (AС) of NW Altai. No island-arc units have ever been reported there. The Zasur'ya AC includes ocean plate stratigraphy (OPS) magmatic and sedimentary rocks of three formations, Listvenny (l. Cambrian), Talitsa (Tremadocian) and Marcheta (Floian), which age was constrained by microfossils. The OPS assemblage includes basalt, pelagic chert and hemipelagic siliceous mudstone and siltstone, and sandstone. We analyzed zircons in five samples. The distributions of U Pb ages of detrital zircons from five samples of sandstones are all unimodal with main peaks at ca. 488 Ma (Listvenny Fm.), 491 Ma (Talitsa Fm.) and 485 Ma (Marcheta Fm.). The Precambrian ages are very few. The maximum deposition ages inferred from the youngest populations of zircon ages are ca. 464 Ma. Compositionally, the sandstones are greywackes or feldspar litharenites. The Listvenny and Talitsa sandstones are higher silicic (SiO 2av. = 68.5 wt%) compared to Marcheta samples (SiO 2av. = 60.5 wt%). The major and trace element features of all sandstones are similar to supra-subduction intermediate-felsic (Listvenny, Talitsa) and mafic-intermediate (Marcheta) magmatic rocks. All samples yielded positive values of zircon ɛHf(t) (+4.3 to +20.1) and bulk-rock ɛNd(t) (+0.6 to +4.8) indicating juvenile magmatic rocks in the provenance. However, the Listvenny and Talitsa samples show lower ɛNd(t) (1.3 and 0.8, respectively) than those of the Marcheta Fm. (4.7). Probably the Zasur'ya sandstones were deposited in a back-arc basin (Listvenny, Talitsa), and fore-arc basin (Marcheta). All Zasur'ya greywacke sandstones were derived by destruction of a single late Cambrian - Early Ordovician intra-oceanic arc. The Zasur'ya intra-oceanic arc was identified in NW Altai for the first time and it represents a new site of juvenile crustal growth in the CAOB. [ABSTRACT FROM AUTHOR]

Among the four palynozones established for the Pennsylvanian–Permian sedimentary succession of the Paraná Basin, two are related to the glacial (AcZ: Ahrensisporites cristatus and CmZ: Crucisaccites monoletus zones) and one is related to the following terminal glacial phase (VcZ: Vittatina costabilis Zone) in this portion of Gondwana. The AcZ and the CmZ are typically recognized within the basal and middle portions of the Itararé Group and the Aquidauana Formation, while the VcZ corresponds to the upper portions of both units. In this paper we present a palynostratigraphic analysis of all occurrences of these palynozones from 66 boreholes and 29 outcrops. Two paleogeographic maps are depicted showing the distribution of all sections where the palyonozones related to glacial and terminal glacial sections occur within the Itararé Group and the Aquidauana Formation. Glacial palynozones (AcZ and CmZ) are recognized from outcrops and boreholes from Santa Catarina, Paraná, São Paulo, Mato Grosso do Sul, Mato Grosso and Goiás states, encompassing the thickest portion of the Itararé Group and the Aquidauana Formation. The terminal glacial palynozone (VcZ) was recognized from several boreholes and outcrops, well distributed throughout the basin, from the Rio Grande do Sul, Santa Catarina, Paraná, São Paulo and Mato Grosso do Sul states. Reworked palynomorphs from Devonian and Mississippian strata found together with indigenous species in assemblages assigned to the glacial palynozones (AcZ and CmZ) are used herein as a tool for interpretation of the source area and as indicators of transport direction. As observed elsewhere in Gondwana, palynozones related to the glacial and terminal glacial phases present dominance of spores and monosaccate pollen grains, whereas those linked to the latter phase record the income and the quantitative increase of certain species indicative of progressive climate amelioration. Further sedimentary and stratigraphical aspects are also discussed. [ABSTRACT FROM AUTHOR]

A diverse and exceptionally preserved fossil association occurs in Campáleo Outcrop black shales of the upper Itararé Group, correlated to the Lontras Member, considered representative of the Pennsylvanian–Permian transition in the Paraná Basin, Brazil. In this paper, we present the palynological records from 20 stratigraphic horizons of these shales and related strata, which revealed 21 taxa of spores, 33 of pollen grains, two species of fungi, one species of Chlorophyceae and two species of Prasinophyceae. The section is correlated to the Vittatina costabilis Zone, due to the records of certain guide species, such as Converrucosisporites confluens , Illinites unicus and several species of Vittatina. An additional subsurface section (TC-4 core) partially correlated with the Campáleo Outcrop and comprising the passage of the Crucisaccites monoletus and Vittatina costabilis palynozones was also studied in order to support the stratigraphic positioning. Once combined with the stratigraphic positioning in the basal portion to the Lontras Shale, it allows us to consider it around the Pennsylvanian–Permian boundary, probably in the Gzhelian to age of the Campáleo Outcrop. We observed distinct palynofloristic compositions from (i) the rhythmic shale with dropstones (basal portion) and from (ii) the fossiliferous black shales (upper portion). The former presents a large dominance (about 90 %) of pollen grains (xerophylous elements) and low frequency (about 7 %) of spores (meso-hygrophylous), while the results of the latter are conversely. Marine palynormorphs were recorded herein only from the rhythmic shale. The palynological assemblages on the base of the Campáleo Outcrop demonstrated a more intense sediment supply, bringing sporomorphs from more distant regions being represented mainly by xerophylic flora, indicating the existence of regions devoid of ice cover, where forests could develop, as occur in seasonal climate regions. The upper level of the Campáleo Outcrop characterizes one of the predominance of spores (hygrophylic communities) in these palynological associations supported by the large number of insects found that indicates proximity to the coastline, little transport (spore tetrads), poor contribution of more distant continental sediments (low expressiveness of pollen grains) and low salinity water, due to the absence of marine palynomorphs, representing a reducing restricted marine environment. This data integrated with the stratigraphic context and other geological data evidenced changes in sea level due to the climatic oscillations in the course of the LPIA that influenced the sediment supply and the distance of the coastline in this region of the Paraná Basin. [Display omitted] • Palynology from a fossil-Lagerstätte section in the Paraná Basin (Campáleo Outcrop) • The Campáleo Outcrop is considered of the age Gzhelian to Pennsylvanian-Permian boundary based on palynological associations • The section is interpreted as part of an epicontinental sea under deglacial conditions [ABSTRACT FROM AUTHOR]

The Argentinean Andean foreland region between latitudes 31°S to 33.5°S presents an intense crustal and upper mantle seismic activity that was recorded by a local seismological network called CHARSME (Chile Argentina SeisMic Experiment), and was used to obtain new velocity determinations. In a first moment, from 4 P-wave velocity (V P) models proposed by other authors, the detail in the layers was increased, resulting in better models used as initial model in the investment. Finally, by carefully selecting a set of earthquakes, a simultaneous velocity inversion, hypocentre determination and station correction were performed using the VELEST code. In order to obtain better velocity models (V P and V S) and V P /V S ratio, different tests were carried out in all processes. The final V P model presented in this paper incorporates considerations made in other seismological studies. This model accurately determined velocities between 10 and 65 km depth. The upper mantle velocity (V P) was defined in 8.05 km/s. From the Wadatti diagram, which represents a line whose slope is related to the wave velocities and the Poisson's coefficient, a V P /V S value of 1.732 was obtained. Alternative V P /V S values were also considered to invert V P , V S and V P /V S simultaneously. The minimum detailed model of V P , V S and V P /V S decreased the RMS by 25% relative to the initial models, implying an improvement in the uncertainty of locations. The new and precise locations of crustal earthquakes allowed defining clusters within Cuyania, a tectonic terrain that collided to Gondwana in the Early Paleozoic. Although it is known that foreland seismicity is mainly concentrated in this terrain, this work shows that there are well-defined zones within Cuyania that are more seismically active. Earthquakes of intermediate depth (upper mantle) are strongly agglomerated in the flat-slab zone of the subducting Nazca Plate. The discontinuities present in our model suggest upper, middle and lower crustal structuring, as well as a marked contrast between the sediments and the underlying basement. It was possible to interpret an upper crust consisting of sediments and basement to a depth of 25 km, a middle crust between 25 and 45 km and a lower crust between 45 and 55 km. We also defined the Mohorovičić (Moho) discontinuity at 55 km depth. The crustal velocities are in agreement with previous seismological studies. • The minimum detailed model of VP, VS and VP/VS reduced the RMS by 25% compared to the initial models. • Minimal one-dimensional models allowed us to obtain more precise locations of the hypocentres. • Our locations show that the crustal earthquakes there are located in well-defined seismically active sectors. • Upper mantle earthquakes are strongly agglomerated in the flat-slab zone of the subducting Nazca Plate. [ABSTRACT FROM AUTHOR]

The upper Paleozoic gas reservoir in the Daniudi gas field, Ordos Basin, is one of the typical tight sandstone gas reservoirs in China. Research into the sequential order of reservoir densification and gas accumulation is the key to revealing the formation mechanism of tight sandstone gas reservoirs. However, this scientific issue is still a subject of debate in the Daniudi gas field. Based on a series of reservoir experiments and in combination with stratigraphic burial and thermal maturity history, a comprehensive study is conducted on the formation and natural gas accumulation processes of the upper Paleozoic sandstone reservoir in the Daniudi gas field. Study results indicate that the main causes of sandstone reservoir densification of the study area include long-term compaction, multistage quartz cementation and carbonate cementation. In accordance with the time order of reservoir densification and gas accumulation, the formation of tight gas reservoirs can be divided into two types: self-sourced and near-source accumulations. In the former, before sandstone reservoir densification occurs, low-maturity natural gas generated from coal rocks and dark mudstones enter the reservoir quickly, migrate towards structural highs as driven by buoyancy, and then accumulate and form gas reservoir in favourable lithologic traps. In the latter, after tight sandstone reservoirs are formed, high- maturity gas migrates along fractures formed in the Late Cretaceous and accumulate in the nearby reservoir with micro-fractures. The study results provide a new understanding of the formation process of tight sandstone gas reservoirs and provides a reference for the exploration and development of the same type gas reservoirs. [ABSTRACT FROM AUTHOR]

The Longshou Shan, located in western China, plays a crucial role in connecting the Tarim Continent with the North China Craton. It provides valuable insights into the Cenozoic intracontinental deformation, the complex dynamics of Eurasian tectonics, and the relationship between the pre-Cenozoic Tethys and Central Asian orogenic systems. Consequently, comprehending the evolution of the Phanerozoic era in this region holds immense significance. Zircon (U-Th)/He (ZHe) dating was conducted on three granite samples (n = 18) collected from the Longshou Shan. The ZHe dates of these granite rocks range from 7.2 to 517.7 Ma, showing a negative correlation with eU values. Furthermore, a limestone sample from the Longshou Shan yielded ZHe (n = 4) ages of 172.0–277.1 Ma and AHe (n = 4) ages of 17–111.9 Ma. The area has undergone complex tectonic processes involving multiple phases of uplift and burial. Using both forward and inverse modeling methods, we aim to establish plausible thermal histories. Our models reveal: (1) Late Paleozoic unroofing; (2) Early Mesozoic cooling and Late Mesozoic regional stabilization; and (3) Cenozoic reheating and subsequent cooling. By investigating the intricate thermal history of the Longshou Shan through multi-method modeling, we compare different approaches and assess the capabilities of single ZHe dating for understanding a thermal history. This research contributes to unraveling the region's geological complexities and aids in evaluating various modeling methods. [ABSTRACT FROM AUTHOR]

The Niutitang Formation of the lower Cambrian (Є1n) is a target reservoir of shale gas widely developed in China's Middle-Upper Yangtze region, with the characteristics of being widely distributed, having a big thickness and highly organic carbon abundance. However, the exploration and research degree are relatively low. Based on extensive core sample, experimental test results, drilling, and field outcrop surveying, the shale gas generation capacity, gas content, and gas composition are discussed. The preservation conditions of shale gas are then systematically analyzed from the aspects of tectonic movement, fault development, structural style, and thermal evolution degree. The results show that the organic-rich shale with a thickness ranging from 40 to 150 m developed in the mid-lower part of the Є1n Formation, with the TOC content values ranging from 0.4% to 14.64%. While it has unfavorable characteristics of a high thermal evolution, with Ro values ranging from 1.92% to 5.74%, a low gas content and a high nitrogen content (70% wells). The Є1n shale gas has complex preservation conditions. The Є1n Formation has good roof-to-floor conditions, but after the main gas generating peak of the Є1n shale during the Jurassic–Cretaceous, the most intensive tectonic activity of the Yanshan movement resulted in poor preservation conditions (faults developed and cap rock fractured). The huge faults extended to the surface are formed due to tectonic movement in an extensional environment, and the structural style and development are the main factors affecting the preservation conditions of the Є1n shale gas. Additionally, the high thermal evolution of the Є1n shales also has a certain impact on the preservation conditions. Therefore, the stable area far from large faults (>2.0 km), with weak local tectonic activity and tectonic deformation, is the favorable area for shale gas preservation in the Є1n Formation. [ABSTRACT FROM AUTHOR]

Three species assigned to the same nominal genus of Paleozoic xenacanthiform shark have been combined with the name Orthacanthus gracilis (Chondrichthyes, Xenacanthiformes, Orthacanthidae). Orthacanthus gracilis (Giebel, 1848), which was originally combined as Chilodus gracilis Giebel, 1848, is the senior synonym; it has priority over both Orthacanthus gracilis (Newberry, 1857), which was originally combined as Diplodus gracilis Newberry, 1857, and Orthacanthus gracilis Newberry, 1875a. Proposed species-group replacement names are Orthacanthus lintonensis nom. nov. for O. gracilis (Newberry, 1857) and Orthacanthus adamas nom. nov. for O. gracilis Newberry, 1875a. Chilodus gracilis Giebel, 1848 is designated as the type species of Chilodus Giebel, 1848; this species becomes the type species for Giebelodus Whitley, 1940, which is a replacement name for Chilodus Giebel, 1848 (preoccupied by Chilodus Müller & Troschel, 1844, Actinopterygii). Giebelodus Whitley, 1940 is a junior subjective synonym of Orthacanthus Agassiz, 1843. [ABSTRACT FROM AUTHOR]

This article examines the geotectonic and sedimentary features of the Upper Devonian–Carboniferous–Permian deposits of the North Caspian basin, represented by deposits of marine Paleozoic-isolated carbonate platforms formed during the subsidence of the basement on the passive continental margin. The top is covered by thick salt-bearing Kungurian deposits from the end of the Early Permian epoch. The formation of carbonate platforms is associated with a major tectonic restructuring of the basin at the turn of the Caledonian and Hercynian eras, when the Paleo-Tethys Ocean was formed and isolated carbonate islands began to grow in an open marine environment. The central part of the depression experienced a long and gradual subsidence that spanned the entire Paleozoic era and the beginning of the Mesozoic era. In the south and east, from the Devonian to the Permian periods, barriers were formed in the form of island carbonate massifs that separated the North Caspian basin from the Paleo-Tethys Ocean. During the formation of the salt-bearing basin, these barriers limited water exchange and ensured a one-way influx of sea water from the open ocean. As a result, at the end of the Permian period, thicker salts accumulated; however, during the collision of the continental massifs, an invasion of many kilometers of redbeds occurred. They initially stopped salt accumulation; however, gradually, in the north of the Caspian Sea during Roadian times, the salt accumulation continued. The post-Roadian time is associated with the influx of large quantities of redbed sediments, which caused gravitational instability in the underlying salt, and salt tectonics began with the formation of domal structures. [ABSTRACT FROM AUTHOR]

The northern Appalachians record accretion of Laurentia‐ and Gondwana‐derived terranes to Laurentian margin during the formation of Pangea. Terrane bounding structures, key to reconstructing this history, are poorly understood at depth. We use teleseismic receiver functions to probe the crust beneath Appalachian terranes in Québec and Maine. We identify an eastward‐dipping intra‐crustal boundary extending beneath the trace of the Iapetus Ocean closure that separates the peri‐Laurentian Dunnage and the peri‐Gondwanan Gander terranes. Systematic fabric in rocks is a likely cause of anisotropic seismic properties associated with it. Depth and position associate this boundary with a previously identified décollement separating authochtonous Laurentian basement from rocks emplaced during Pangea's assembly. Neither the décollement nor the crust‐mantle boundary under our profile change beneath the surface trace of the Iapetus Ocean closure, suggesting that it has been transported to the northwest relative to the actual boundary between mantle lithospheres of former Laurentia and Gondwana. Plain Language Summary: Approximately 250 million years ago, the supercontinent Pangea included most of the Earth's landmass. The northern Appalachians of Québec and Maine were in the center of Pangea and preserve a record of its assembly in the surface rocks and the deep structure of the lithosphere. Rock outcrops on the surface enable the crust to be subdivided into regions (terranes) that originated as parts of proto‐continents Laurentia and Gondwana. An ocean called Iapetus separated those continents and the trace of its eventual closure is recognized in the surface rocks of the region. We probe the structure beneath the trace of Iapetus Ocean closure using seismic waves from distant earthquakes that traverse the upper layers of the Earth and provide information on their properties. We identify a zone of well‐developed rock fabric that likely originated when blocks of Earth's crust moved relative to each other as Pangea was put together. This dipping boundary (called décollement) extends beneath the trace of the Iapetus Ocean closure without interruption, documenting a mismatch between the record of Pangea's assembly preserved on the surface and the deeper structure of the continent. Our findings are instructive for understanding how the supercontinent cycle, a process unique to Earth, operates. Key Points: Crustal structure of northern Appalachians in Québec and Maine probed using receiver function methodEast‐dipping intra‐crustal boundary with evidence of systematic rock fabric underlies peri‐Laurentian Dunnage and peri‐Gondwanan Gander terranesBoundary separating lithospheres of former Laurentia and Gondwana at depth is east of the surface trace of Iapetus Ocean closure [ABSTRACT FROM AUTHOR]

Tectonic setting of the Late Carboniferous Cameng Formation in the north of South Qiangtang terranes (SQT) remains controversial. Here, we report new geochemical results for clastic rocks from the Cameng Formation. Our results show that the Index of Compositional Variability (ICV) is greater than 1, indicating these sediments experienced limited recycling and were probably derived from acid to intermediate magmatic rocks. The extent of weathering, with the Index of CIA vary from 67 to 75 (mean = 71), ICV > 1 (mean = 1.25) and the Th/U ratios > 4, is moderate in the source area. These new findings show that the Cameng Formation was most likely deposited in an unstable environment (continental island arc or active continental margin). Combined with other evidence, we further infer that the Early Paleozoic rocks (206Pb/238U ages varying from 438 to 502 Ma) presently exposed in the South Qiangtang terrane are the potential source of the Late Carboniferous depositions in the northern SQT, and were most likely deposited in a forearc basin under the in situ suture model, that is, the southward subduction of the Longmu Co-Shuanghu Tethys Ocean beneath the SQT. [ABSTRACT FROM AUTHOR]

Class Demospongiae is the largest in the phylum Porifera (Sponges) and encompasses nearly 8,000 accepted species in three subclasses: Keratosa, Verongimorpha, and Heteroscleromorpha. Subclass Heteroscleromorpha contains ∼90% of demosponge species and is subdivided into 17 orders. The higher level classification of demosponges underwent major revision as the result of nearly three decades of molecular studies. However, because most of the previous molecular work only utilized partial data from a small number of nuclear and mitochondrial (mt) genes, this classification scheme needs to be tested by larger datasets. Here we compiled a mt dataset for 136 demosponge species—including 64 complete or nearly complete and six partial mt-genome sequences determined or assembled for this study—and used it to test phylogenetic relationships among Demospongiae in general and Heteroscleromorpha in particular. We also investigated the phylogenetic position of Myceliospongia araneosa, a highly unusual demosponge without spicules and spongin fibers, currently classified as Demospongiae incertae sedis, for which molecular data were not available. Our results support the previously inferred sister-group relationship between Heteroscleromorpha and Keratosa + Verongimorpha and suggest five main clades within Heteroscleromorpha: Clade C0 composed of order Haplosclerida; Clade C1 composed of Scopalinida, Sphaerocladina, and Spongillida; Clade C2 composed of Axinellida, Biemnida, Bubarida; Clade C3 composed of Tetractinellida; and Clade C4 composed of Agelasida, Clionaida, Desmacellida, Merliida, Suberitida, Poecilosclerida, Polymastiida, and Tethyida. The inferred relationships among these clades were (C0(C1(C2(C3+C4)))). Analysis of molecular data from M. araneosa placed it in the C3 clade as a sister taxon to the highly skeletonized tetractinellids Microscleroderma sp. and Leiodermatium sp. Molecular clock analysis dated divergences among the major clades in Heteroscleromorpha from the Cambrian to the Early Silurian, the origins of most heteroscleromorph orders in the middle Paleozoic, and the most basal splits within these orders around the Paleozoic to Mesozoic transition. Overall, the results of this study are mostly congruent with the accepted classification of Heteroscleromorpha, but add temporal perspective and new resolution to phylogenetic relationships within this subclass. [ABSTRACT FROM AUTHOR]

The tectonic affinity of the Korean Peninsula in reference to the Permo-Triassic collision of the Sino-Korean Craton (SKC) and the South China Craton (SCC) has been in the center of debates over the last three decades. Since the Imjingang Belt that runs through the middle part of the Korean Peninsula is thought to represent the major tectonic boundary, most part of North Korea, including the "Pyeongnam Basin" in the southern part, has been regarded as part of the SKC. However, differences in stratigraphy and the fossil occurrence have been recognized by local geologists between the southern part of "the Pyeongnam Basin" (SPB) and the northern part of the "Pyeongnam Basin" (NPB), and which have hardly been considered for the paleogeographical affinity of the regions so far. Here we provide a comprehensive review on 1,072 fossil taxa from the Neoproterozoic to middle Paleozoic sedimentary successions of North Korea, and utilize the data for determining tectonic affinity of the regions. Especailly, Cambrian trilobite genera from the SPB and NPB have been quantitatively compared with those of North China (the SKC) and the SCC, using similarity indices, the non-metric multidimensional scaling (NMDS), and PerMANOVA test. The results have revealed that the SPB is tied to the SCC, not to North China (the SKC), whereas the NPB is closely related to North China. The SCC affinity of the SPB is corroborated by stratigraphical features, such as the presence of the Precambrian–Cambrian boundary and the middle Paleozoic strata, which are largely absent in the SKC. Our results demonstrate that the SPB region likely originated from to the SCC, and thus further suggest that the collisional boundary of supracrustal rocks between the SKC and the SCC in the Korean Peninsula corresponds to the boundary of the NPB and the SPB. Accordingly, the extent of the newly-defined Pyeongnam Basin is restricted to the traditional NPB region. The SPB region is included in the extent of the newly-proposed Hwanghae District, which is bounded to the east with the Imjingang Belt by the Ryesonggang Fault. The South China Craton-originated rocks of the Hwanghae District and the Imjingang Belt are collectively termed the South China-affinity terrane (SAT). [ABSTRACT FROM AUTHOR]

Many studies convincingly documented the diagnostic morphology of Scolicia, establishing a functional link with the burrowing activities of heart urchins, common components of the marine mobile faunas that emerged during the Mesozoic Marine Revolution. However, this ichnotaxon has been repeatedly mentioned in both continental successions and Paleozoic marine strata, even though its diagnostic characteristics were absent. This approach may reflect the implicit belief that behavioural convergence is rampant in the ichnologic record and can be uncritically adopted in almost all cases. We underscore the importance of a definition of Scolicia that is based on diagnostic morphologic features and supported by a solid analysis from the perspective of function and mode of construction. This view of Scolicia highlights its value in paleoenvironmental reconstructions and its significance to unravel macroevolutionary trends. Attribution to an ichnotaxon should involve understanding of morphologic features in terms of its mode of production rather than the mere observation of superficial similarities. [ABSTRACT FROM AUTHOR]

The Punjab Platform is a gently dipping monocline that has been drilled since the 1960s with a low success ratio. Most of the drilling targets in the past were based on the structural interpretation. Furthermore, the exploration focus remained in Paleozoic sequences, and little attention has been paid to the Cretaceous systems. In this paper, a prograding Cretaceous (Sembar-Goru) mega-sequence is subdivided into three sequences using a semi-automated and integrated workflow. A data-driven chronostratigraphic chart is prepared, which revealed several regressive stages in the study area. The sands developed during these stages are laterally sealed by shales and claystones that form a stratigraphic play. The stratigraphic play area lies in a shoreface environment where shoreface sands are expected to be charged by underlying Lower Cretaceous black shales. A prominent gas cap above the proposed stratigraphic play further increases the confidence on the presence of a reservoir. This paper is the first attempt to study the Cretaceous deltaic sequences in the study area, which has remained unexplored for the last six decades. [ABSTRACT FROM AUTHOR]

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This paper attempts stratigraphic characterization of the Early Cambrian Abbottabad Formation exposed in the Sherwan area, west of Abbottabad. A regional correlation is carried out with the rest of the Early Paleozoic sequences exposed in northern Pakistan including Abbottabad, Peshawar basin and Salt Range. Stratigraphic sections are measured at Aluli, Pind Khan Khel and Bir villages in the mapped area and at Soban Gali and Muslimabad (Sirbon Hill), Abbottabad. A three-fold subdivision of the Abbottabad Formation has emerged through this study; a) lower arenaceous unit (dominantly quartzite with subordinate pebbly conglomerate, sandstone and siltstone), b) middle dolomitic unit (dominantly dolomite with subordinate quartzite, siltstone, and conglomerate) and c) upper quartzite unit. The three members defined in this study are exclusively preserved in the Sherwan area. Elsewhere, either the only lower two members are preserved such as at the Soban Gali and Sirbon Hill, Abbottabad or only the upper two units are present such as at Swabi in the Peshawar basin. In the latter, the Misri Banda Quartzite that has an Ordovician paleontological age but ~525 Ma age defined by the youngest detrital zircon is possibly an equivalent of the upper quartzite member of the Abbottabad Formation defined in this study. The two are lithologically similar and the detrital zircon age resemble closely with the age of the Abbottabad formation. [ABSTRACT FROM AUTHOR]

The present paper deals with a tectonic event of Late Ordovician age affecting three blocks of China, i.e. South China, North China and Tarim. In the North China and the Tarim platforms, as well as their marginal belts, there was a regional uplift during the early Katian Stage of the Ordovician. The uplift was indicated by the unconformities between the Ordovician successions and overlying late Paleozoic strata. New biostratigraphic studies of conodonts and graptolites from many sections at Longxian and Yaoxian, North China shows that the youngest Ordovician strata are of the early Katian age corresponding to graptolite Diplacanthograptus spiniferus Biozone. The same level has been recognized to represent the uppermost Ordovician in the platform area of Tarim, whereas in the marginal belt the top boundary of the Ordovician is slightly younger, corresponding to the graptolite Dicellograptus complanatus Biozone. Thus, the regional uplift in North China and Tarim is shown by the disconformity between the early Katian strata and Late Paleozoic strata, the onset coinciding with that of the Kwangsian Orogeny in South China. The designation Kwangsian Orogeny later fell into disuse and was replaced by the term Caledonian Orogeny. However, in terms of geographic location, tectonic nature, and the timing of activity, the Caledonian Orogeny differs significantly from the orogenic event in South China, and the continued use of this term in South China is inappropriate and misleading. [ABSTRACT FROM AUTHOR]

The paper presents results from a range of petroleum exploration studies carried out in Jordan - some regional in approach, others focussed on the NE of the country - together with a review of existing literature and industry reports. The dominant active structural feature in Jordan is the NNW-SSE striking Dead Sea Transform, characterised in southern Jordan by extensional splay fault arrays, pull-apart basins and relay-sag basins. Elsewhere in the country there are regional-scale strike-slip faults (ENE-WSW, NNW-SSE) with multiple phases of reactivation. Stratigraphic studies have identified potential reservoir intervals within the Lower Palaeozoic Salib, Umm Sahm, Disi and upper Dubaydib (Risha Sandstone Member) Formations, and also within the Triassic and Cretaceous intervals. Potential source rocks occur within the Lower Palaeozoic Burj, lower Hiswa and Dubaydib Formations and at basal and Upper Silurian levels, with limited additional potential in the Triassic and possibly Permian successions. Apatite fission track analysis (AFTA), zircon fission track analysis (ZFTA) and vitrinite reflectance (VR) studies of selected wells and outcrop samples indicate that the thermal history of eastern Jordan is dominated by the effects of two major periods of relatively deep burial, with subsequent exhumation phases beginning in the Late Palaeozoic and Late Cenozoic. An intermediate episode (Mesozoic) of deep burial and exhumation is possible. Significant variations in heat flow regimes and burial patterns occur in different parts of Jordan, probably controlled by deep structure and burial history. Over much of the north of the country, the Lower Palaeozoic succession is in the gas window and the underlying section is overmature. The main hydrocarbon generation and expulsion phase in this region was in the Late Palaeozoic and was terminated by 'Hercynian' (Late Palaeozoic) uplift. Further south, the Silurian and Upper Ordovician sections are in the oil window, and deeper source intervals are mature for gas. The Triassic interval is a valid hydrocarbon play in the NW and NE of Jordan, with oil sourced from either Permian, Triassic or Cretaceous kitchens. Upper Cretaceous source rocks within the thicker Mesozoic sections in the Azraq Graben are in the oil window and have sourced the small-scale Hamza oilfield. In addition to the known widespread Upper Cretaceous - Paleocene oil shale potential in Jordan, the Ordovician and Silurian sections have potential for shale gas in northern Jordan and for shale oil further south. [ABSTRACT FROM AUTHOR]

This paper examines the geological structure and metallogeny of Neoproterozoic to Paleozoic basins overlying Precambrian massifs in the eastern part of the Central Asian Tectonic Belt, including the South Sinegorsk basin and the Kabarga trough of the Khanka massif, the Kimkan trough of the Jiamusi-Lesser Hinggan massif, and the Melgin trough of the Turan-Zhangguangcailing massif. The ages of these basins are dated on assemblages in the succession, the age and relationships of Paleozoic intrusive complexes are described, and the ages of the ores and associated alteration assemblages have been defined using radiogenic isotopes. The Neoproterozoic to Paleozoic basins share a number of common geological features. Their basement is composed of Archean to early Proterozoic gneisses and crystalline schists metamorphosed at granulite and amphibolite facies. The lower successions of the basins (PR2–€1) comprise highly carbonaceous siliciclastic and carbonate rocks of terrigenous origin intercalated with ferruginous quartzites and manganese ores. Middle–upper Cambrian to Ordovician–Silurian successions are composed of terrigenous rocks. The upper part of the succession reflects the wide distribution of Devonian to Carboniferous volcanogenic and sedimentary–volcanogenic assemblages, except in the Kimkan trough, where they were most likely eroded. Basin development was terminated by emplacement of granites and leucogranites of the Carboniferous Kuibyshevka, Troitsk and Tyrma–Bureya intrusive complexes to which some mineral resources are related. Two discrete metallogenic epochs are recognised. An early Paleozoic epoch is characterised by pyrite, beryllium–fluorite, tantalum-bearing and tin greisen deposits. A late Paleozoic epoch displays the wide distribution of uranium and molybdenum–uranium mineralisation in quartz–sericite metasomatites and clay alteration halo and, to a lesser degree, polymetallic vein and molybdenum occurrences, tantalum and niobium deposits in apogranites. [ABSTRACT FROM PUBLISHER]

This paper considers the results of mineralogical, geochemical, and geochronological studies of leucogabbroids of the Karagai Massif located within the Lesser Khingan superterrane of the Central Asian fold belt. The main features of the rock-forming minerals of the gabbroids are the high calcium content of the clinopyroxene corresponding in composition to diopside-salite (WoEnFs) or augite (WoEnFs), the high basicity of the plagioclase (An), and the presence of primary magmatic magnesian hornblende. The age of the massif was determined by U-Pb zircon dating as 257 ± 1 Ma. The compositional peculiarities of the gabbroids indicate that they were most probably formed in island-arc or active continental margin settings. With allowance for the existing geodynamic reconstructions and the data obtained in the present study, the formation of the Late Paleozoic gabbroids of the Karagai Massif was presumably related to the final stages of the subduction processes that preceded the collapse of the terranes of the eastern Central Asian fold belt. [ABSTRACT FROM AUTHOR]

This paper reviews the anatomical evidence of medullosalean foliage known from cuticles and coal balls, and discusses what it tells us about the systematics and palaeoecology of the parent plants. Medullosalean foliage shows more diversity in epidermal anatomy than in any other group of gymnospermous seed-plants, especially in the configuration of subsidiary cells around the stomata, the detailed structure of the hairs, and the shapes of the cells. Diagnostic for the order are the fronds typically having dorsiventral pinnules supported by rachises with a dissected stele, resin canals in both rachises and pinnules, and distinctive epidermal hairs consisting of a single row of many cells. Foliage anatomy is of little value for distinguishing medullosalean families but is useful for distinguishing genera and species. Anatomy also provides insights into the autecology of the plants. A number of features previously regarded as xeromorphic are re-interpreted as adaptations to high-humidity conditions (stomata sunken or protected by papillae, papillae on lower surface of leaf). Different species could grow in either shaded or well-illuminated positions, indicated by the absence or presence of a hypodermis below the upper epidermis. Few species show evidence of defensive strategies against herbivory except possibly in juvenile fronds. Evidence from stomatal distribution and structure for determining variation in atmospheric CO2 is equivocal but may indicate a rise in CO2 levels in early Stephanian (latest Moscovian) times. [ABSTRACT FROM PUBLISHER]

The water balance of the mesocenozoic aquifers of the Algarve, in the south of Portugal has traditionally been estimated considering only direct ("autogenic") recharge from rainfall occurring in the area of the aquifers. Little importance has been attributed to so-called allogenic recharge, originating from streambed infiltration from runoff generated outside the aquifers, particularly in the Palaeozoic rocks to the north where runoff is high. The Querença-Silves (QS) aquifer is the most important aquifer of the region both for irrigation and public water supply. Several important and sensitive surface/groundwater ecotones and associated groundwater dependent ecosystems exist at the springs of the natural discharge areas of the aquifer system. A numerical flow model has been in constant development over the last few years and currently is able to reproduce the aquifer's responses to estimated direct recharge and abstraction for the years 2001--2010. However, recharge calculations for the model do not take into account allogenic recharge infiltration along influent reaches of streams. The quantification of allogenic recharge may further improve the assessment of water availability and exploitation risks. In this paper an attempt is made to quantify the average annual contribution of allogenic recharge to the QS aquifer, based on monitoring data of the principal water courses that cross the aquifer system. Significant uncertainties related to surface runoff generated within the aquifer area, as well as areal recharge were identified and the consequences for the optimization of spatial distribution of transmissivity in the groundwater flow model are also addressed. [ABSTRACT FROM AUTHOR]

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Highlights • Novel processing of broadband relative permittivity and conductivity logs. • Proposed Markov-chain Monte-Carlo inversion method is robust in shale formation. • Saturation, water conductivity, and surface conductance of clay are continuously estimated. • Estimated hydrocarbon saturation is between 20% and 90%. • Brine conductivity of the shale formation ranges from 0.1 to 0.25 S/m. Abstract An organic-rich shale gas formation generally exhibits high clay content, high total organic carbon (TOC), low porosity, high tortuosity, and the presence of conductive pyrite that adversely affect the well-log-derived hydrocarbon saturation estimations. In the presence of such petrophysical conditions, log-derived hydrocarbon saturation estimates obtained from multi-mineral analysis solver and various subsurface electromagnetic (EM) logs, such as induction resistivity log, dielectric permittivity log, or dielectric dispersion logs, are not consistent and can vary up to 0.5 saturation unit for a single depth. In addition, hydrocarbon saturation estimates derived from EM logs using conventional saturation models tend to break down in organic-rich shale gas formation because of the unaccounted interfacial polarization effects of clays and conductive minerals. Several of the above-mentioned issues can be addressed by processing downhole broadband EM dispersion logs using a mechanistic clay-pyrite interfacial-polarization model to accurately estimate hydrocarbon saturation in organic-rich shale gas formations. EM induction resistivity, logging while drilling (LWD) propagation, and dielectric dispersion logging tools were jointly deployed in a well drilled in an organic-rich shale gas formation to acquire continuous broadband EM dispersion measurements at 7 EM-log-acquisition frequencies for a total depth of 1500 m in the well. This was the first ever acquisition of broadband EM dispersion logs, comprising relative permittivity and conductivity measured at the 7 EM-log-acquisition frequencies. In this paper, a new Markov-chain Monte-Carlo-based (MCMC) stochastic inversion scheme coupled with a clay-pyrite interfacial-polarization (IP) model is used to process the EM broadband dispersion logs, and simultaneously estimate hydrocarbon saturation, connate water conductivity, and surface conductance of clay in the shale gas formation. The proposed Markov-chain Monte Carlo-based stochastic inversion scheme is robust to noise and exhibits fast convergence. The estimated hydrocarbon saturation is also compared against those derived from resistivity log, dielectric dispersion logs, and multi-mineral analysis solver. The estimated hydrocarbon saturation, connate water conductivity, and surface conductance of clay in two specific intervals of the shale gas formation are in the ranges of 0.2–0.9, 0.1 S/m–0.25 S/m, and 1 × 10−7 S–1 × 10−6 S, respectively. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Basin inversion occurred in the Late Carboniferous in the Aqishan-Yamansu belt. • Fe-Cu mineralization may have occurred during the basin inversion. • Fe and Cu mineralization was separated. • External sulfur would be involved in the Cu mineralization. Abstract The formation of the Eastern Tianshan orogen (northern Xinjiang, NW China) with a number of EW-trending mineralization belts was closely linked to the evolution of the Junggar and South Tianshan oceans, probably part of the Paleo-Asian Ocean. Among these Eastern Tianshan mineralization belts, the Carboniferous Aqishan-Yamansu Fe (-Cu) belt hosts a total reserve of 207 Mt Fe and economic Cu endowments for many deposits. These Fe (-Cu) deposits are hosted in submarine volcanic rocks (Lower Carboniferous Yamansu Formation and Upper Carboniferous Tugutublak Formation) and are featured by the presence of extensive skarn alteration without apparently-causative intrusive rocks, which leads to debates over their genesis. In this paper, we have summarized the ore deposit geology, geochemistry and stable isotopes of the Aqishan-Yamansu Fe (-Cu) deposits and discuss their genesis under the regional tectonic framework. We suggest that the Carboniferous Aqishan-Yamansu belt may have been a forearc basin formed by the south-dipping subduction of the Kangguer Ocean beneath the Central Tianshan massif. The Yamansu Formation volcanic rocks and some syngenetic Fe deposits may have formed during the opening of the forearc basin. The Tugutublak Formation volcanic rocks and most Fe (-Cu) deposits may have formed during the subsequent Late Carboniferous basin inversion. In these Aqishan-Yamansu Fe (-Cu) deposits, the Fe mineralization occurred earlier and was likely formed directly from the magmatic-hydrothermal fluids, whereas the subsequent Cu mineralization was likely caused by the gradual increase of seawater or basinal brine influx into the fluid system (external sulfur). The probable external sulfur input, the absence of clear plutonic link, and the temporal coincidence of peak mineralization and basin inversion for the Carboniferous Aqishan-Yamansu Fe-Cu mineralization are comparable to the Mesozoic IOCG mineralization in the Central Andes. [ABSTRACT FROM AUTHOR]

This introduction outlines the papers collected in the special issue "Evolution and metallogeny of the Sanjiang arc-back arc basin system in the Eastern Tethys." The papers focus on scientific issues from Paleozoic to Cenozoic evolution and metallogeny of the Sanjiang arc-back arc basin system in the Eastern Tethys concerning tectonics, petrology, geochemistry, geochronology and mineral deposits. An evolution and metallogeny of the Sanjiang arc-back arc basin system in the Eastern Tethys is briefly introduced. [ABSTRACT FROM AUTHOR]

The Qilian-Qaidam Orogenic Belt is a component of the western Central China Orogenic Belt, and records a nearly complete evolutionary history of the South Qilian and North Qaidam oceans (branches of the Proto-Tethyan Ocean). However, the timing and process of amalgamation of the microblocks of the western Central China Orogenic Belt and the closure time of the South Qilian and North Qaidam oceans remain uncertain. The Olongbuluke Terrane (OLT), located in the central of the Qilian-Qaidam Orogenic Belt, contains well-developed Precambrian to Paleozoic sedimentary successions that shed light on the tectonic history of these ocean basins. In this paper, detrital zircon U Pb ages combined with ophiolitic, magmatic and high-pressure to ultrahigh-pressure metamorphic records and field investigations, indicate that the OLT was part of a passive continental margin during the early Paleozoic and there was a microblock, named the North Qaidam Terrane (NQT), lying between the Qaidam Block and the OLT. A marked provenance change occurs in the OLT after ca. 517 Ma, which is inferred to record the collision between the OLT and NQT. Later, the North Qaidam oceanic plate subducted under the NQT, and the North Qaidam Ocean closed at ca. 450 Ma. The similar detrital zircon U Pb age spectra of contemporaneous deposit flysch sequences in the Shihuigou Formation (OLT) and the Balonggonggaer Formation (the South Qilian Accretionary Belt) indicates the onset of collision between the OLT and Central Qilian Terrane occurred at ca. 458 Ma. The detrital zircon U Pb age spectra of microblocks from the early Paleozoic strata of the northern Tibetan Plateau share a North Indian affinity, indicating that the closure of the Proto-Tethyan Ocean may relate to the formation of the Gondwanan landmass. • The North Qaidam Terrane may exist between the Qaidam Block and the Olongbuluke Terrane. • The Olongbuluke Terrane collided to the North Qaidam Terrane at ca. 517 Ma. • The onset of collision between the Olongbuluke Terrane and the Central Qilian Terrane at ca. 458 Ma. • The closure of Proto-Tethys may relate to the formation of the Gondwana landmass. [ABSTRACT FROM AUTHOR]