豫西禹县二叠纪大羽羊齿类的演化及其地质意义

豫西禹县二叠纪大羽羊齿类共鉴定有6属24种（包括 2个新属和15个新种）其垂向分布和演化趋向明显,可分为4个演化阶段、2个演化趋向和2个演化系列.作者修正了浅间一男建立的Emplectopteris series,认为Gigantopteris系由Giganlonclea通过Progigantopteris演化而来.根据形态功能与生态环境间的关系,作者认为大羽羊齿类叶形态的演化趋向主要是长期适应滨海热带暖湿气候环境的结果,而不是干旱所致.本区以大羽羊齿为首要分子的3个植物组合带皆可与华北地台北缘、华南及日本等地与海相动物群共生的植物群比较,是对华北地台二叠系进行多重划分的生物地层基础.     

河南登封晚古生代含煤地层各煤组的古生物特征

<正> 河南登封位于华北地台的南缘,区内石炭二叠系厚度大,出露全,分布广泛。根据含煤地层的岩性特征、旋迴规律、煤层结构和煤质差异,近千米的煤系地层共分为九个煤组(表1)。通过11条剖面数千块标本的研究和综合分析,发现9个煤组的生物化石各具特色,易于区别。     

Some Palaeozoic‐Mesozoic stratigraphic‐structural relationships in east timor and their significance in the tectonics of timor

An ‘autochthon’ model for the tectonic development of Timor is suggested, based on observations of Palaeozoic‐Mesozoic relationships from a broad area of central East Timor, including:

1. (a) ‘allochthonous’ Permian rocks unconformable on metamorphic rocks

2. (b) ‘allochthonous’ Permian units interbedded with ‘autochthonous’ Permian units, and

3. (c) ‘autochthonous’ Triassic sediments stratigraphically overlying ‘allochthonous’ Permian rocks.

The model is supported by recent modifications in palaeogeographic interpretations for the Permian of north Australia (e.g. Powell, 1976; Thomas, 1976). Our observations support and extend the earlier suggestions of Grady (1975), and the resulting model is in contrast with some of the hypotheses of Audley‐Charles and his associates (as, most recently, Barber et al., 1977), Fitch & Hamilton (1974), Hamilton (1973, 1976), and Crostella (1976).

Our model involves no essentially allochthonous pre‐Cainozoic material in Timor. The Permian to Cretaceous units are envisaged as developing on the continental margin which was dominantly inactive, but affected to some extent by Late Jurassic rifting activity. Following the Pliocene collision with the Inner Banda Arc, uplift along the collision zone would have caused gravity gliding towards the south. Thus, surficial olistostrome deposits, originally from the island arc, could have eventually moved to the northern slopes of the Timor Trough, while at depth, reverse faulting could have developed as a result of gravity gliding.

We maintain that previous postulates of a pervasive, strongly imbricate structure for Timor, lack adequate substantiation in the literature. Furthermore, accounts of the tectonic development of Timor, involving large scale translation on low angle faults, are even less well substantiated.     

Thermodynamic parameters of CaMgSi2O6-Mg2Si2O6 pyroxenes based on regular solution and cooperative disordering models

Thermodynamic parameters for the reaction: $$\begin{gathered} Mg_2 Si_2 O_6 = Mg_2 Si_2 O_6 \hfill \\ enstatite clinopyroxene \hfill \\ \end{gathered} $$ in the system CaO-MgO-SiO₂ have been deduced from phase equilibrium and enthalpy of solution data. From the regular solution theory, the seventeen currently available reversed experimental compositions of coexisting enstatite and clinopyroxene, presumed to be ordered diopside, lead, by a statistical regression, to the following best fit parameters: ΔH ^o=6.80 kJ ΔS ^o=2.75 J/K W _H ^Cpx =24.47 kJ (regular solution enthalpy parameter) W _V ^Cpx =0.105 J/bar (regular solution volume parameter). The derived parameters are not significantly affected by the (necessary) choice of W ^Opx in the range 20–50 kJ. The above values are in very good agreement with deductions from the solution calorimetry on synthetic CaMgSi₂O₆-Mg₂Si₂O₆ clinopyroxenes of Newton et al. (1979), which also places bounds on possible departures from the optimal values of these parameters. The calorimetric data may also be interpreted in terms of a Bragg-Williams cooperative-disordering model (Navrotsky and Loucks, 1977), in which diopside-structure clinopyroxene and a ‘relaxed’ low-Ca clinopyroxene (‘Fe-free pigeonite’) approach each other in composition, structural state, and stability with increasing temperature. The ΔH ^o parameter deduced from the regular solution theory is reinterpreted as the enthalpy change of enstatite to Mg₂Si₂O₆ pigeonite; the ΔH ^o of the transformation of enstatite to the diopside structure would, in this case, be considerably larger than 6.8 kJ. The curvature of the enthalpy of solution data, explained by the regular solution theory in terms of M2-site energetics (involving W _H ^cpx ), is reinterpreted as due to disordering and ‘relaxation’ in the Navrotsky-Loucks model. Although the regular solution theory with the best-fit parameters accounts for all of the reversed enstatite and diopside compositions to within 18 ° C, and is a convenient representation of the phase equilibria for purposes of geothermometry, the disordering model is, at the present level of knowledge, equally valid and allows for a region of stability of two coexisting clinopyroxenes.     

Fractured space: a geographical reflection on the digital divide

What does it mean to reflect upon space in connection to telecommunications? If we start with a conception of urban space as being fully integrated, including on an equal footing both information and communication technologies (ICT) and mobility techniques, as well as the founding notion of copresence that we find at the heart of all urban organization, we might then be able to examine the notion of the ‘digital divide’ in a new light. This clearly experimental approach is conducted by a research group called ‘Urbatic’, which is composed of geographers who, for the last three years, have been conducting theoretical research whose objective is to take into account two fields of social science: the theory of urbanity and the theory of telecommunication. Surveys conducted in this perspective focus on the analysis of the choices people make between the different means they can use to cope with distances (copresence, mobility and telecommunication) with a view to constructing their own space. The analysis of these choices leads us to propose a new theorized interpretation of the ‘digital divide’.     

Permian Fossil Plants from the Sediments of the Vorkuta Series at the Pechora Coal Basin in the Collection of the Earth Science Museum of Moscow State University

Permian plant remains from the Vorkuta 1 location collected at the Earth Science Museum of the Moscow State University were characterized (at outcrop 38 at the left bank of the Vorkuta River within the boundaries of Vorkuta town opposite the Rudnik settlement). The collection includes equisetophytes Paracalamites decoratus (Eichwald) Zalessky, P. frigidus Neuburg, Paracalamitina cf. striata Zalessky emend. Naug.; Annulina neuburgiana (Radczenko) Neuburg, the leaves of ferns (Pecopteris anthriscifolia (Goeppert) Zalessky, P. helenaeana Zalessky, P. vorcutana Zalessky, and P. cf. leptophylla Bunbury), as well as the leaves of Vojnovskyales Rufloria spp. and, probably, of ginkgophytes. In terms of stratigraphy, the considered plant remains originated from the Inta formations of the Vorkuta series (the Ufa stage of the Biarmian (Middle) subdivision of the Permian system). The collection is characterized by significant scientific, exhibition, and didactic potentialities.     

Violent volcanism,stagnant oceans and some inferences regarding petroleum,strata-bound ores and mass extinctions

Past changes from a well-mixed aerated ocean to a stratified stagnant ocean are indicated by decreasing δ¹³C of limestone (opposite to prior conclusions) as well as by increasing δ³⁴S of marine sulfates. The proposed stagnant ocean model includes a warm CO₂-enriched atmosphere and a bathyal to abyssal marine system dominated by bacterial components in the food web and by consequent ‘light’ carbon in organic material and biogenic carbonates. Culminations of prolonged stagnant episodes correspond with marine faunal extinctions of Late Permian and Late Cretaceous time, and the protracted changes and correlations provide evidence against any hypothesis of mass extinction by sudden worldwide catastrophe, including the asteroid impact hypothesis. The Cretaceous stagnant ocean, taken as the prime example, is attributed to climatic warming triggered by volcanic CO₂ (greenhouse effect) and several feedbacks, including decreased Earth albedo and increased sinking of warm evaporite brines instead of aerated polar waters. Marine extinctions are attributed to upward expansion of the oxygen minimum zone and to catastrophic mixing of surface waters with poisonous sulfidic waters of the deeps. The stagnant ocean provided a counterbalance between deep reduction and shallow oxidation, conditions that favored maximal formation of black sulfidic shales, protopetroleum and sedimentary sulfide ores and shallow to mid-depth barite, phosphorite, iron ore, cherty iron formation, and sulfate-bearing red-beds. Trace elements concentrated in stagnant ocean sediments include chalcophile and Pt-group metals, negating claims that Ir provides a unique ‘fingerprint’ of meteorite impact and cosmic accretion.     

Climbing‐ripple successions in turbidite systems: depositional environments,sedimentation rates and accumulation times

Climbing‐ripple cross‐lamination is most commonly deposited by turbidity currents when suspended load fallout and bedload transport occur contemporaneously. The angle of ripple climb reflects the ratio of suspended load fallout and bedload sedimentation rates, allowing for the calculation of the flow properties and durations of turbidity currents. Three areas exhibiting thick (>50 m) sections of deep‐water climbing‐ripple cross‐lamination deposits are the focus of this study: (i) the Miocene upper Mount Messenger Formation in the Taranaki Basin, New Zealand; (ii) the Permian Skoorsteenberg Formation in the Tanqua depocentre of the Karoo Basin, South Africa; and (iii) the lower Pleistocene Magnolia Field in the Titan Basin, Gulf of Mexico. Facies distributions and local contextual information indicate that climbing‐ripple cross‐lamination in each area was deposited in an ‘off‐axis’ setting where flows were expanding due to loss of confinement or a decrease in slope gradient. The resultant reduction in flow thickness, Reynolds number, shear stress and capacity promoted suspension fallout and thus climbing‐ripple cross‐lamination formation. Climbing‐ripple cross‐lamination in the New Zealand study area was deposited both outside of and within channels at an inferred break in slope, where flows were decelerating and expanding. In the South Africa study area, climbing‐ripple cross‐lamination was deposited due to a loss of flow confinement. In the Magnolia study area, an abrupt decrease in gradient near a basin sill caused flow deceleration and climbing‐ripple cross‐lamination deposition in off‐axis settings. Sedimentation rate and accumulation time were calculated for 44 climbing‐ripple cross‐lamination sedimentation units from the three areas using TDURE, a mathematical model developed by Baas et al. (2000) . For T_c divisions and T_bc beds averaging 26 cm and 37 cm thick, respectively, average climbing‐ripple cross‐lamination and whole bed sedimentation rates were 0·15 mm sec^?1 and 0·26 mm sec^?1 and average accumulation times were 27 min and 35 min, respectively. In some instances, distinct stratigraphic trends of sedimentation rate give insight into the evolution of the depositional environment. Climbing‐ripple cross‐lamination in the three study areas is developed in very fine‐grained to fine‐grained sand, suggesting a grain size dependence on turbidite climbing‐ripple cross‐lamination formation. Indeed, the calculated sedimentation rates correlate well with the rate of sedimentation due to hindered settling of very fine‐grained and fine‐grained sand–water suspensions at concentrations of up to 20% and 2·5%, respectively. For coarser grains, hindered settling rates at all concentrations are much too high to form climbing‐ripple cross‐lamination, resulting in the formation of massive/structureless S₃ or T_a divisions.     

Genesis of granitoid batholiths of Peninsular Malaysia and implications for models of crustal evolution: Evidence from a NdSr isotopic and UPb zircon study

Nd, Sr and U-Pb isotopic data for the late Triassic West Coast Province batholiths and Permian to Triassic East Coast Province batholiths of Peninsular Malaysia allow estimates of the ages of the crustal fragments comprising the peninsula to be made. Initial ?_Nd and ?_Sr values for granitoids from the West Coast Province range from ?6 to ?10 and +160(0.716) to +660(0.751) respectively. Nd model ages calculated based on a depleted mantle evolution model (T_DM^Nd) range from 1300 Ma to 1800 Ma and are in general agreement with the mid-Proterozoic upper intersection ages of U-Pb zircon reverse discordia (1500–1700 Ma). Initial ?_Nd and ?_Sr values for granitoids from the East Coast Province range from ?0.8 to ?6 and +10(0.705) to +130(0.714) respectively. Calculated T_DM^Nd ages of 900–1400 Ma for these granitoids are comparable to two U-Pb zircon reverse discordia intercepts that yield 800 Ma and 1350 Ma. The general agreement of U-Pb zircon inheritance ages and T_DM^Nd ages are interpreted to correspond to the Proterozoic ‘crust formation’ ages of the continental fragments represented by the West Coast and East Coast batholithic provinces. Mid-Proterozoic (~ 1300–1900 Ma) ‘crust formation’ ages are commonly shown by other Phanerozoic continental margin plutonic and volcanic belts. The ubiquitous mid-Proterozoic ‘crust formation’ ages and the absence of Archaean signatures suggest voluminous juvenile additions to the continental crust in the mid-Proterozoic. Such ages at continental margins would imply that many continental blocks had achieved very much their present-day extent by the mid-Proterozoic.     

Dentary groove morphology does not distinguish ‘Nanotyrannus’ as a valid taxon of tyrannosauroid dinosaur. Comment on: “Distribution of the dentary groove of theropod dinosaurs: Implications for theropod phylogeny and the validity of the genus Nanotyrannus Bakker et al., 1988”

There has been considerable debate about whether the controversial tyrannosauroid dinosaur ‘Nanotyrannus lancensis’ from the uppermost Cretaceous of North America is a valid taxon or a juvenile of the contemporaneous Tyrannosaurus rex. In a recent Cretaceous Research article, Schmerge and Rothschild (2016) brought a new piece of evidence to this discussion: the morphology of the dentary groove, a depression on the lateral surface of the dentary that houses neurovascular foramina. They argued that an alleged ‘Nanotyrannus’ specimen, which possesses a groove, cannot be referable to Tyrannosaurus rex, which they considered as lacking the groove, and they hypothesized that ‘Nanotyrannus’ is closely related to albertosaurine tyrannosauroids, which also are said to possess the groove. However, we show that the groove is a widespread feature of tyrannosauroids that is present in T. rex and many other specimens, and that it is an ontogenetically variable feature that changes from a sharp, deeply-impressed groove to a shallower sulcus as an individual matures. As a result, the presence or absence of a dentary groove does not clarify the validity of ‘Nanotyrannus’ or its phylogenetic position among tyrannosauroids. We consider it most parsimonious that ‘Nanotyrannus’ specimens belong to juvenile T. rex.     

Germination and seedling growth of corn (Zea mays l.) under varying levels of copper and zinc

The heavy metal tolerance in corn (Zea mays L.) var. ‘Neelum’ was assessed at germination and seedling growth after having subjected it to different concentrations of CuSO₄ and ZnSO₄. Germination was not affected by any of the metal tested, whereas initial growth was strongly inhibited by increasing concentrations of ZnSO₄. Seedlings developed toxicity symptoms in the presence of both metals but more chlorotic and necrotic regions were observed at varying levels of ZnSO₄ than CuSO₄. The metal accumulation was concentration dependent. Z. mays seedlings accumulated more copper in roots but greater contents of zinc in their shoots. On the basis of results presented here, it can be concluded that the cultivar of the species tested has shown a marked sensitivity to the presence of small amounts of metals present in the growth medium. The data support the assumption that metal sensitivity is probably due to strong tendency of the species to accumulate them. This justifies that the corn variety ‘Neelum’ is not suitable for the cultivation under situations where water and soil suffer from occasional and/ or transitory metal pollution.     

Morphological consequence of Gangamopteris McCoy in Glossopteris flora

The leaves of Gangamopteris McCoy are the dominant constituent of Glossopteris flora in Lower Permian sequences of Gondwana. Morphologically leaves are similar with Glossopteris Brongniart in having reticulate venation pattern but differ in the absence of midrib. Large number of plant fossils collected from the carbonaceous shale samples of Barakar coal seams (Lower Gondwana) of Satpura Gondwana Basin, India indicates the presence of number of specimens of Gangamopteris belonging to sixteen species including two new species viz., Gangamopteris sethiaensis sp. nov. and Gangamopteris satpuraensis sp. nov.The morphological diversity, stratigraphical distribution and character affiliation of Gangamopteris demonstrate its organizational involvement towards the development of Glossopteris and signify the evolutionary lineage in Glossopteridales.     

Splendid isolation: ‘Philosopher’s islands’ and the reimagination of space

This paper argues that the metaphorical figure of the island plays an important but profoundly ambiguous role in the imagination of social space. The paper argues that ‘utopic’ islands have historically provided a fictional domain of experimentation that has informed the constitution of ‘real’ state spaces. From the 16th to 20th centuries this took the form of an increasingly consolidated and ‘global’ endotopia: a world, exemplified by the ‘political’ map, full of state spaces constituted as interiors. More recently, islands have served a very different metaphoric function, being used to create and legitimise spaces of exteriority – ‘xenospaces’ such as the online worlds of the ‘metaverse’ and the arcane legal/financial spaces of offshore – which in combination constitute an emergent xenotopia. The ‘philosopher’s island’ (Mackay, 2010), therefore, represents a complex and polyvalent spatial form that serves to continuously and expediently redefine the nature of social space.     

The most ancient member of the Sequoioideae – the new genus Krassilovidendron Sokolova,Gordenko et Zavialova (Cupressaceae s.l.) from the Albian–Cenomanian of Western Siberia (Russia)

The new genus Krassilovidendron Sokolova, Gordenko et Zavialova with the type species Krassilovidendron fecundum Sokolova, Gordenko et Zavialova is described on the basis of numerous compressions of polymorphic shoots in organic connection with seed and pollen cones from the Albian–Cenomanian of the Kubaevo locality (Russian Federation, Kemerovo region, Western Siberia). The new taxon is characterized by an assemblage of features that distinguishes it from all known extant and fossil conifer genera: shoots with helically arranged leaves varying from amphistomatic small scale-like leaves to strictly epistomatic linear-lanceolate leaves; terminal, ellipsoidal to obovate seed cones, bearing 14–26 helically arranged peltate bract-scale complexes (bract and ovuliferous scale are completely fused) with a cylindrical vascular bundle, bifurcating into abaxial and adaxial dichotomizing bundles; up to 22 inverted seeds of various shapes with a protruding micropyle and inconspicuous lateral wings, which are arranged in two to five arcuate rows; solitary terminal pollen cones with helically arranged microsporophylls, each bearing four abaxial microsporangia; and small pollen grains with a relatively short papilla, numerous orbicules on the surface, and a three-layered ectexine with a tectum of strongly fused granules, an infratectum of smaller and more loosely arranged granules, and a thin footlayer. The new taxon possesses a combination of characters indicating it belongs to the subfamily Sequoioideae. Krassilovidendron shares the greatest number of features with Sequoia Endlicher and Sequoiadendron Buchholz, and fewer characters with Metasequoia Miki ex Hu et W.C. Cheng.     

Exclusion (and seclusion): geographies of disowned widows of India

Geographies of disowned Indian widows are highly under-researched. This case study seeks to understand the lives of 21 of the many diverse widows across India. These 21 widows were driven out by their families, who sought refuge in the two Briddhha Ashrams (old-age hermitages) namely Rajkya and Birla, both located in the heritage city, Varanasi, Uttar Pradesh. Drawing upon ethnographic research and building on 21 semi-structured interviews, the research aims to understand the lives of these widows in the two ashrams and their everyday coping strategies. The findings suggest that each woman has negotiated with ‘widowhood’ in order to build individual identities as ‘self’. Using the threads of analysis, we urge for the passing of the draft Bill on widows’ protection, welfare and maintenance prepared by Dr. Bindeshwar Pathak, the architect of sanitation charity, Sulabh International, who has adopted widows of Varanasi and Vrindavan by providing a dole of INR2000/month.     

Are the Chinese Altai “terranes” the result of juxtaposition of different crustal levels during Late Devonian and Permian orogenesis?

The general structure of the Chinese Altai has been traditionally regarded as being formed by five tectono-stratigraphic ‘terranes’ bounded by large-scale faults. However, numerous detrital zircon studies of the Paleozoic volcano-sedimentary sequences shown that the variably metamorphosed Cambro-Ordovician sequence, known as the Habahe Group, is present at least in four ‘terranes’. It structurally represents deepest rocks unconformably covered by Devonian and Carboniferous sedimentary and volcanic rocks. Calc-alkaline, mostly Devonian, granitoids that intruded all the terranes revealed their syn-subduction related setting. Geochemistry and isotope features of the syn-subduction granitoids have shown that they originated mainly from the melting of youthful sediments derived from an eroded Ordovician arc further north. In contrast, Permian alkaline granitoids, mostly located in the southern part of the Chinese Altai, reflect a post-subduction intraplate setting. The metamorphic evolution of the metasedimentary sequences shows an early MP-MT Barrovian event, followed by two Buchan events: LP-HT mid-Devonian (ca. 400–380 Ma) and UHT-HT Permian (ca. 300–270 Ma) cycles. The Barrovian metamorphism is linked to the formation of a regional sub-horizontal possibly Early Devonian fabric and the burial of the Cambro-Ordovician sequence. The Middle Devonian Buchan type event is related to intrusions of the syn-subduction granitoids during an extensional setting and followed by Late Devonian-Early Carboniferous NE-SW trending upright folding and crustal scale doming during a general NW-SE shortening, responsible for the exhumation of the hot lower crust. The last Permian deformation formed NW-SE trending upright folds and vertical zones of deformation related to the extrusion of migmatites, anatectic granitoids and granulite rocks, and to the intrusions of gabbros and granites along the southern border of the Chinese Altai. Finally, the Permo-Triassic cooling and thrust systems affected the whole mountain range from ca. 265 to 230 Ma. In conclusion, the Chinese Altai represents different crustal levels of the lower, middle and upper orogenic crust of a single Cambro-Ordovician accretionary wedge, heterogeneously affected by the Devonian polyphase metamorphism and deformation followed by the Permian tectono-thermal reworking event related to the collision with the Junggar arc. It is the interference of Devonian and Permian upright folding events that formed vertical boundaries surrounding the variously exhumed and eroded crustal segments. Consequently, these crustal segments should not be regarded as individual suspect terranes.     

New haramiyidan and reptile fossils from a Rhaetian bedded sequence close to the famous ‘Microlestes’ Quarry of Holwell,UK

We describe here new Late Triassic haramiyidan mammaliaform and reptile fossils from near the classic ‘Microlestes’ Quarry’ at Holwell, Somerset, U.K., where Charles Moore discovered a huge collection of microvertebrates in the 1850s. Moore’s discoveries included the haramiyid Thomasia (formerly ‘Microlestes’ and Microcleptes) for which he achieved worldwide fame. Subsequently, despite much fossicking by researchers at Holwell, few new identifiable specimens of mammaliamorphs and lepidosaurs have been recorded and these were by Kühne in 1939. The new finds described here from a bedded sequence, not from a fissure, add significantly to our knowledge of the Holwell tetrapods and to the Rhaetian terrestrial faunas of the SW U.K. Our discovery of haramiyidan teeth includes a previously unknown type of Theroteinus, a genus not previously recorded from outside of the St-Nicholas-de-Port locality in France. An archosaur tooth, possibly from a phytosaur, is also recorded. The new lepidosaur specimens add significant detail to the recently described ‘basal’ rhynchocephalian Penegephyrosaurus curtiscoppi as well as demonstrating that the global diversity of Lepidosauria in the Late Triassic remains incompletely known.     

Orthomagmatic quartz and post-magmatic carbonate veins in a reported porphyry copper deposit,Andean Intrusive Suite,Livingston Island,South Shetland Islands

A previously reported porphyry Cu + Mo deposit in an Eocene pluton within the South Shetland Island magmatic arc has been re-interpreted as three distinct hydrothermal assemblages. The oldest assemblage (1) exsolved under confinement from the deep (～6 km?) cooling magma whereas assemblages (2) and (3) formed during tectonic ± magmatic episodes at depths of < 1.5 km in the late Cenozoic. The three assemblages occur over the 5 × 11 km mapped in Barnard Point tonalite pluton. Assemblage (1) comprises shallowly dipping sheets of aplite, biotite + tourmaline pegmatite, massive ‘grey’ quartz, and quartz + tourmaline + bornite + chalcopyrite + molybdenite veins. Magnetite + tourmaline + chalcopyrite breccias have associated biotite, K-feldspar and muscovite alteration. Fluid inclusions indicate formation from hot (～600°C), saline (40 equivalent weight % NaCl + CaCl₂) aqueous-carbonic fluids that exsolved from the partly consolidated magma. The primary control on solution chemistry and nature of fracturing was the depth of pluton emplacement. Assemblage (2) consists of steep, vuggy veins and country-rock breccias, with thick propylitic alteration selvages, cemented by microcrystalline quartz, complex inter-growths of FeMg carbonate, bladed barite and trace amounts of bornite and chalcopyrite. These rocks, previously described as breccia (sensu ‘pebble’) dykes in the porphyry complex, are reinterpreted as an influx of moderately hot (175–330°C), weak to moderately saline (2–21 EWP NaCl), aqueous-carbonic fluids that underwent isobaric boiling at 0.8 to 1.3 km depth. Assemblage (3) consists of thin, hematitic fault infillings formed during a second episode of brittle faulting.     

Stratigraphy,biostratigraphy and C-isotopes of the Permian–Triassic non-marine sequence at Dalongkou and Lucaogou,Xinjiang Province,China

Measured lithostratigraphic sections of the classic Permian–Triassic non-marine transitional sequences covering the upper Quanzijie, Wutonggou, Guodikeng and lower Jiucaiyuan Formations at Dalongkou and Lucaogou, Xinjiang Province, China are presented. These measured sections form the framework and reference sections for a range of multi-disciplinary studies of the P–T transition in this large ancient lake basin, including palynostratigraphy, vertebrate biostratigraphy, chemostratigraphy and magnetostratigraphy. The 121 m thick Wutonggou Formation at Dalongkou includes 12 sandstone units ranging in thickness from 0.5 to 10.5 m that represent cyclical coarse terrigenous input to the lake basin during the Late Permian. The rhythmically-bedded, mudstone-dominated Guodikeng Formation is 197 m and 209 m thick on the north and south limbs of the Dalongkou anticline, respectively, and 129 m thick at Lucaogou. Based on limited palynological data, the Permian–Triassic boundary was previously placed approximately 50 m below the top of this formation at Dalongkou. This boundary does not coincide with any mappable lithologic unit, such as the basal sandstones of the overlying Jiucaiyuan Formation, assigned to the Early Triassic. The presence of multiple organic δ¹³C-isotope excursions, mutant pollen, and multiple algal and conchostracan blooms in this formation, together with Late Permian palynomorphs, suggests that the Guodikeng Formation records multiple climatic perturbation signals representing environmental stress during the late Permian mass extinction interval. The overlap between the vertebrates Dicynodon and Lystrosaurus in the upper part of this formation, and the occurrence of late Permian spores and the latest Permian to earliest Triassic megaspore Otynisporites eotriassicus is consistent with a latest Permian age for at least part of the Guodikeng Formation. Palynostratigrahic placement of the Permian–Triassic boundary in the Junggar Basin remains problematic because key miospore taxa, such as Aratrisporites spp. are not present. Palynomorphs from the Guodikeng are assigned to two assemblages; the youngest, from the upper 100 m of the formation (and the overlying Jiucaiyuan Formation), contains both typical Permian elements and distinctive taxa that elsewhere are known from the Early Triassic of Canada, Greenland, Norway, and Russia. The latter include spores assigned to Pechorosporites disertus, Lundbladispora foveota, Naumovaspora striata, Decussatisporites mulstrigatus and Leptolepidites jonkerii. While the presence of Devonian and Carboniferous spores and Early Permian pollen demonstrate reworking is occurring in the Guodikeng assemblages, the sometimes common occurrence of Scutasporites sp. cf. Scutasporites unicus, and other pollen, suggests that the Late Permian elements are in place, and that the upper assemblage derives from a genuine transitional flora of Early Triassic aspect. In the Junggar Basin, biostratigraphic data and magnetostratigraphic data indicate that the Permian–Triassic boundary (GSSP Level) is in the middle to upper Guodikeng Formation and perhaps as high as the formational contact with the overlying Jiucaiyuan Formation.     

Leaiid conchostracans from the uppermost Permian strata of the Paraná Basin,Brazil: Chronostratigraphic and paleobiogeographic implications

Conchostracan fossils are abundant and relatively diversified in the Rio do Rasto Formation (Passa Dois Group, Paraná Basin, southern Brazil), but leaiids (‘Leaia pruvosti’ [Reed, F.R.C., 1929. Novos Phyllopodos Fósseis do Brasil. Boletim do Serviço Geológico e Mineralógico do Brasil 34, 2–16]) were previously found at only one locality of the formation in the northern Santa Catarina State. New specimens of the Family Leaiidae, collected from two outcrops in central Paraná State near the top of the formation, stimulated a revision of related taxa. Both the new and the previously known leaiids are herein assigned to Hemicycloleaia mitchelli [Etheridge Jr., R., 1892. On Leaia mitchelli Etheridge. Proceedings of the Linnean Society of New South Wales 7, 307–310] based on the presence of three carinae and subovate shape. This species was originally recorded in the upper Tatarian (Wuchiapingian, Late Permian) of Sydney Basin, eastern Australia and therefore corroborates the interpretation that the leaiid bearing strata of the Rio do Rasto Formation cannot be younger than Permian. H. mitchelli possibly was one of the most widespread, eurytopic and conservative Late Paleozoic conchostracans of Gondwana (although records from Africa, India and Antarctica must still be confirmed) and it was also found in the Tatarian of Russia. The sudden disappearance of leaiids after their apparent success is consistent with the hypothesis about the biotic crisis around the Permo-Triassic boundary.