Middle Permian brachiopods from the Dongujimqinqi area, Inner Mongolia, China

A small collection of brachiopods is described from the lower Middle Permian Yanchibeishan Formation of the Dongujimqinqi area, eastern Inner Mongolia, China. This fauna consists of the following four species: Kochiproductus sp., Linoproductus simensis (Tschernyschew), Rhynchopora inconstantis Lee and Gu and Licharewia grewingki (Netschajew). The Dongujimqinqi fauna exhibits a strong Boreal-type aspect and suggests an early Middle Permian in age.<br /

Volcanic Age and Geochemistry of the Permian Linxi Formation in Northeast China: Implications for the Tectonic Evolution of the Paleo-Asian Ocean

The tectonic evolution of the Paleo-Asian Ocean (PAO) has been well studied, including its gradual narrowing and closure by subduction. However, aspects of the tectonic evolution of the oceanic domain remain unclear, including the exact timing and nature of the closure. The Central Asian Orogenic Belt (CAOB) was formed by the closure of the PAO and, therefore, contains information about the tectonic evolution of the oceanic domain. Here, we report a study of the petrology, geochronology, and geochemistry of the Taohaiyingzi section of the Permian Linxi Formation in Alukhorqin Banner (Northeast China) in the central part of the CAOB. A newly discovered andesitic tuff from the lower part of the Linxi Formation yields a weighted mean 206Pb/238U age of 262.2 ± 1.1 Ma (n = 87), indicating that the lower part of the Linxi Formation of the Taohaiyingzi section was deposited during the late Guadalupian. Provenance weathering indicators show that the sedimentary rocks of the Linxi Formation are of low maturity. Element geochemical characteristics indicate that the Linxi Formation clastic rocks were derived from eroded magmatic rocks that formed in a continental arc setting and were deposited close to the arc in a continental arc basin environment. The active margin setting was generated by the subduction of the paleo-Asian oceanic plate beneath the Xilinhot–Songliao block. The inferred palaeosalinity of the sedimentary environment changed gradually from brackish to fresh water, suggesting the end of oceanic plate subduction during the late Guadalupian, and the closure of the PAO during or after the Lopingian

Earliest Wuchiapingian (Lopingian, Late Permian) brachiopods in southern Hunan, South China : implications for the Pre-Lopingian crisis and onset of Lopingian recovery / radiation

The uppermost 5-15 m of the Douling Formation in the southern Hunan area. South China, yields a diverse fauna comprised of ammonoids, bivalves, and brachiopods. The brachiopods reported in this paper consist of 51 species in 34 genera and are dominated by the Lopingian (Late Permian) species associated with a few species persisting from the underlying Maokouan (Late Guadalupian). This fauna is of earliest Wuchiapingian in age as precisely constrained by the associated conodont Clarkina postbitteri postbitteri and the Guadalupian-type ammonoid fauna of the Roadoceras-Doulingoceras Zone in the brachiopod horizon. The discovery of the Lopingian species-dominated brachiopod fauna in the earliest Wuchiapingian in southern Hunan suggests a much less pronounced effect of the pre-Lopingian crisis (end-Guadalupian mass extinction) than the end-Changhsingian mass extinction in terms of brachiopods, a contemporaneous onset of the Lopingian recovery/radiation during the pre-Lopingian crisis period, and taxonomic selectivity of the pre-Lopingian crisis in terms of different fossil groups. New taxa are Echinauris doulingensis n. sp., Pararigbyella quadrilobata n. gen. and n. sp. and P. doulingensis n. gen. and n. sp. <br /

The Lopingian series in the Lhasa Block, Tibet and its palaeogeographical implications

Latest investigation indicates that the Lopingian Series including both terrestrial and marine deposit s are developed in the Lhasa Block. The marine Lopinigian Series in the Lhasa Block contains the compound coral Waagenophyllum, fusulinid Reichelina, and foraminifer Colaniella faunas , and the terrestrial Lopingian Series is characterized by both Cathaysian floras and mixed floras consisting of Gondwanan element s such as Glossopteris , Noeggerathiopsis, Phyllotheca and Cathaysian elements such as Pecopteris ,Sphenopteris. An anlaysis of the Lopingian sequences in the Lhasa Block reveals that it experienced a regression stage f rom Guadalupian to Lopingian. By contrast , the Himalayan Tethys Zone south to the Lhasa Block is characterized by typical Gondwanan Glossopteris flora , coldwater brachiopod and solitary coral faunas. In addition, the Lopingian sequence in the Himalayan Tethys Zone reflect s a transgressive process from the terrestrial Qubu Formation to the shallow marine Qubuerga Formation. Therefore, the Lhasa Block shows significant differences in both biota and depositional features from the Himalayan Tethys Zone during the Lopingian, which implies that the Lhasa Block had rifted from the northern periGondwanan margin before the Lopingian. <br /

A biogeographically mixed, Middle Permian brachiopod fauna from the Baoshan Block, Western Yunnan, China

A small brachiopod fauna is described from the carbonate rocks of the basal Shazipo Formation of the Baoshan Block, western Yunnan, south-west China, including significant new ventral and dorsal internal morphological features of Cryptospirifer omeishanensis Huang. This fauna is regarded as Wordian (Middle Guadalupian, Middle Permian) because of the presence of Cryptospirifer omeishanensis Huang and associated fusulinids (Neoschwagerina craticulifera Zone). Palaeobiogeographically, the brachiopod fauna is of considerable interest because of its admixed nature characterized by typical warm-water Cathaysian elements intermingled with temperate Peri-Gondwanan taxa. This in turn is interpreted to indicate that the Baoshan Block may have been situated in an intermediate palaeogeographical position between Gondwanaland to the south and Cathaysia to the north during the Mid Permian and, as such, it probably furnished an important \u27stepping stone\u27 for the dispersal of Mid Permian eastern Tethyan marine invertebrate taxa (e.g. Cryptospirifer) to the western Tethys.<br /

Chonetoidea (Brachiopoda) from the Lopingian (Late Permian) of South China

en species of the superfamily Chonetoidea from the Lopingian (Late Permian) of South China are described or revised. A review of all recorded Chonetoidea species from the Lopingian (Late Permian) of South China indicates that some 22 species of five genera can be recognised. Species of Tethyochonetes and Neochonetes are characteristic in the lithofacies dominated by mudstone, siltstone or siliceous rocks in the Lopingian and some argillaceous limestone and clay rock facies near the Permian-Triassic boundary. New taxa are Neochoneles (Zhongyingia) subgen. nov., Neochonetes (Huangichonetes) subgen. nov. and Tethyochonetes flatus sp. nov. <br /

Robust portfolio selection based on a multi-stage scenario tree

The aim of this paper is to apply the concept of robust optimization introduced by Bel-Tal and Nemirovski to the portfolio selection problems based on multi-stage scenario trees. The objective of our portfolio selection is to maximize an expected utility function value (or equivalently, to minimize an expected disutility function value) as in a classical stochastic programming problem, except that we allow for ambiguities to exist in the probability distributions along the scenario tree. We show that such a problem can be formulated as a finite convex program in the conic form, on which general convex optimization techniques can be applied. In particular, if there is no short-selling, and the disutility function takes the form of semi-variance downside risk, and all the parameter ambiguity sets are ellipsoidal, then the problem becomes a second order cone program, thus tractable. We use SeDuMi to solve the resulting robust portfolio selection problem, and the simulation results show that the robust consideration helps to reduce the variability of the optimal values caused by the parameter ambiguity.

Robust Portfolio Selection Based on a Multi-stage Scenario Tree

The aim of this paper is to apply the concept of robust optimization introduced by Bel-Tal and Nemirovski to the portfolio selection problems based on multi-stage scenario trees. The objective of our portfolio selection is to maximize an expected utility function value (or equivalently, to minimize an expected disutility function value) as in a classical stochastic programming problem, except that we allow for ambiguities to exist in the probability distributions along the scenario tree. We show that such a problem can be formulated as a finite convex program in the conic form, on which general convex optimization techniques can be applied. In particular, if there is no short-selling, and the disutility function takes the form of semi-variance downside risk, and all the parameter ambiguity sets are ellipsoidal, then the problem becomes a second order cone program, thus tractable. We use SeDuMi to solve the resulting robust portfolio selection problem, and the simulation results show that the robust consideration helps to reduce the variability of the optimal values caused by the parameter ambiguity