Dong-Xun Yuan

Discovery of a Sphaeroschwagerina fusuline fauna from the Raggyorcaka Lake area, northern Tibet: implications for the origin of the Qiangtang Metamorphic Belt

The Qiangtang Metamorphic Belt (QMB) was considered to have either formed in situ by amalgmation of the North and South Qiangtang blocks or been underthrust from the Jinsha suture and exhumed in the interior of a single ‘Qiangtang Block’. A new Sphaeroschwagerina fusuline fauna discovered in the Raggyorcaka Lake area supports the interpretation that the North and South Qiangtang blocks were separated by a wide ocean during Asselian (Early Permian) time, indicating that the QMB was formed by the suturing of the Palaeotethys Ocean along the Longmu Co-Shuanghu suture.

Permian Fusuline Fauna from the Lower Part of the Lugu Formation in the Central Qiangtang Block and its Geological Implications

A Kubergandian (Kungurian) fusuline fauna from the lower part of the Lugu Formation in the Cuozheqiangma area, central Qiangtang Block is described. This fusuline fauna belongs to the Southern Transitional Zone in palaeobiogeography, and is characterised by the presence of the distinctive bi-temperate genus Monodiexodina and many genera common in lower latitude Tethyan areas such as Parafusulina and Pseudodoliolina. The occurrence of Monodiexodina in the fauna confirms that the seamount-type carbonates of the Lugu Formation did not originate from the Palaeotethys Ocean, but rather from a branch of the Neotethys Ocean after the rifting of the Qiangtang Block from the Tethys Himalaya area in the Artinskian.

First records of Wuchiapingian (Late Permian) conodonts in the Xainza area, Lhasa Block, Tibet, and their palaeobiogeographic implications

Yuan, D.X., Zhang, Y.C., Zhang, Y.J., Zhu, T.X. & Shen, S.Z., 2014. First records of Wuchiapingian (Late Permian) conodonts in the Xainza area, Lhasa Block, Tibet, and their palaeobiogeographic implications. Alcheringa 38, 546–556. ISSN 0311-5518. Conodonts are among the best fossil groups to provide high-resolution biostratigraphic correlation and resolve the palaeobiogeographic evolution of the Permian. However, they have been rarely reported from the Lhasa Block in Tibet. Here we report the first discovery of Wuchiapingian (early Lopingian) conodonts from the Xiala Formation in the Lhasa Block, Tibet. This conodont fauna includes two genera and three species (Clarkina liangshanensis, C. orientalis, Iranognathus sp.). The conodont fauna indicates that the Xiala Formation previously assigned to the Guadalupian actually ranges from late Kungurian to late Wuchiapingian. The existence of the late Wuchiapingian conodont species Clarkina orientalis and C. liangshanensis in the Lhasa Block provides additional data to support the viewpoint that this block probably had been in a warm-water regime during the Wuchiapingian (Lopingian). Dong-Xun Yuan [yuanzi55@163.com], School of Earth Sciences and Engineering, Nanjing University, 22 Hankou Road, Nanjing, 210093, PR China and State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, 39 East Beijing Road, Nanjing, 210008, PR China; Yi-Chun Zhang [yczhang@nigpas.ac.cn] and Shu-Zhong Shen [szshen@nigpas.ac.cn] (corresponding author), State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, 39 East Beijing Road, Nanjing, 210008, PR China; Yu-Jie Zhang [zebiac@163.com] and Tong-Xing Zhu [ztongxing88@yahoo.com.cn], Chengdu Center, China Geological Survey, 2 Renming Road North, Chengdu, 610081, PR China. Received 9.1.2014; revised 1.4.2014; accepted 28.4.2014.

Artinskian (Early Permian) fusuline fauna from the Rongma area in northern Tibet: palaeoclimatic and palaeobiogeographic implications

Zhang, Y.C., Wang, Y., Zhang, Y.J. & Yuan, D.X., 2013. Artinskian (Early Permian) fusuline fauna from the Rongma area in northern Tibet: palaeoclimatic and palaeobiogeographic implications. Alcheringa 37, 529–546. ISSN 0311–5518. A fusuline fauna consisting of ten species in five genera from the Qudi Formation of the Jiaomuri and Gangtangcuo sections in the Rongma area, northern Tibet, is described. This fauna contains a few typical Peri-Gondwanan fusuline species such as Pseudofusulina pamirensis, Neodutkevitchia insignis and N. sp. cf. N. tumidiscula. The fauna is dated as Artinskian based on the presence of both genera Chalaroschwagerina and Praeskinnerella. The Peri-Gondwanan fusuline fauna in the Qiangtang Block is grouped palaeobiogeographically into the Southern Transitional Zone, which is located in the southern part of the Peri-Gondwanan blocks during the late Sakmarian and Artinskian. Moreover, the occurrence of the Peri-Gondwanan fusuline fauna, the lithological transition from glacimarine deposits to carbonates, and the Peri-Gondwanan fusulines’ apparent southeastward migration from the Kalmard Block of central Iran during the Artinskian, are interpreted here to be the result of global warming after the peak of the Late Palaeozoic Ice Age. Yi-chun Zhang [geozyc@yahoo.com], School of Life and Environmental Sciences, Deakin University, Melbourne Burwood Campus, 221 Burwood Highway, Burwood, Victoria 3125, Australia; State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, 39 East Beijing Road, Nanjing 210008, PR China; Yue Wang [yuewang@nigpas.ac.cn], State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, 39 East Beijing Road, Nanjing 210008, PR China; Yu-jie Zhang [zebiac@163.com], Chengdu Center, China Geological Survey, 2 Renming Road North, Chengdu 610081, PR China; Dong-xun Yuan [yuanzi55@163.com], State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, 39 East Beijing Road, Nanjing 210008, China; Department of Earth Sciences, Nanjing University, 22 Hankou Road, Nanjing 210008, PR China. Received 12.3.2013; revised 2.5.2013; accepted 12.5.2013.

Revised Wuchiapingian conodont taxonomy and succession of South China

Abstract. South China has become the most important area to establish a global stratigraphic framework of the Wuchiapingian Stage because complete Wuchiapingian sequences include the GSSPs for the base and top of the stage. As the markers of the Wuchiapingian GSSP, conodonts are the most important fossil group to establish the Wuchiapingian biostratigraphic framework. However, few documents have investigated in detail the conodont biostratigraphic succession through the entire Wuchiapingian Stage. Furthermore, the conodont taxonomy of several Wuchiapingian Clarkina species is still debated. Therefore, we here review all Wuchiapingian Clarkina species from South China and figure ontogenetic growth series from juvenile to adult individuals for each valid and important species in order to revise both Wuchiapingian conodont taxonomy and the biostratigraphic succession. Based on the Penglaitan, Dukou, and Nanjiang sections, seven conodont zones (Clarkina postbitteri postbitteri, C. dukouensis, C. asymmetrica, C. leveni, C. guangyuanensis, C. transcaucasica, and C. orientalis) are recognized. The Wuchiapingian Clarkina species lineage is also reviewed to confirm the conodont biostratigraphic framework. The Guadalupian-Lopingian boundary (GLB) interval represents a sequence boundary. The time framework of the pre-Lopingian extinction interval indicates that the beginning of the end-Guadalupian regression is in the upper part of the Jinogondolella postserrata Zone, and the beginning of the early Lopingian transgression is in the lower part of the Clarkina dukouensis Zone in South China.

LOPINGIAN (LATE PERMIAN) BRACHIOPOD FAUNAS FROM THE QUBUERGA FORMATION AT TULONG AND KUJIANLA IN THE MT. EVEREST AREA OF SOUTHERN TIBET, CHINA

Permian strata containing abundant brachiopods are well developed in the Himalaya Tethys Zone. However, relatively few has been systematically described due to the difficult working condition for collecting. In this paper, we describe the brachiopods from the Qubuerga Formation at the Tulong and Kujianla sections in southern Tibet. The brachiopod faunas consist of 15 species belonging to 11 genera. Among the identified 15 species, Retimarginfera xizangensis , Costiferina indica , Fusispirifer semiplicatus , Spiriferella sinica , Biplatyconcha grandis and Neospirifer ( Quadrospina ) tibetensis are very common in the equivalents of the Himalaya Tethys Zone including the Selong Group at the Selong Xishan and Qubu sections in southern Tibet, the Senja Formation in northwest Nepal, the Zewan Formation in Kashmir, and the upper part of the Wargal Formation and the Chhidru Formation in the Salt Range, Pakistan. They are all comparable and can be assigned to the Wuchiapingian- early Changhsingian. Since the brachiopods from the Qubuerga Formation at Tulong and Kujianla are all composed of typical Gondwanan, bipolar or cosmopolitan elements, it is conclusive that the Himalaya Tethys Zone in the northern margin of the Indian Plate was still situated at southern high-latitudes under cold palaeoclimatic conditions during most of the Lopingian. The faunal succession at Tulong also recorded a rapid warming at the very end of the Changhsingian in view of the fact that the typical cold-water Lopingian brachiopod, gastropod and bivalve faunas were dramatically replaced by extremely abundant conodonts Clarkina in the basal part of the dolostone unit of the Tulong Formation. This end-Changhsingian warming is comparable with that recorded throughout the Permian-Triassic boundary interval at Selong, Qubu in southern Tibet, the Salt Range, Pakistan and the sections in Kashmir as well as South China.