MIDDLE PERMIAN FUSULINES FROM THE THITSIPIN FORMATION OF SHAN STATE, MYANMAR AND THEIR PALAEOBIOGEOGRAPHICAL AND PALAEOGEOGRAPHICAL IMPLICATIONS by YI-CHUN ZHANG 1 , KYI PYAR AUNG 2 , SHU-ZHONG SHEN 3 , HUA ZHANG 1 , THAN ZAW 4,5 , LIN DING 4,6 , FU-LONG CAI 4 and KYAING SEIN 5 1 State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology & Center for Excellence in Life & Paleoenvironment, Chinese Academy of Sciences, 39 East Beijing Road, Nanjing 210008, China; yczhang@nigpas.ac.cn 2 Department of Geology, Banmaw University, Kachin State, Myanmar 3 School of Earth Sciences & Engineering, Nanjing University, Nanjing 210023, China 4 Key Laboratory of Continental Collision & Plateau Uplift, Institute of Tibetan Plateau Research, Beijing 100101, China 5 Myanmar Geosciences Society, Yangon, Myanmar 6 Center for Excellence in Tibetan Plateau Earth Sciences, Chinese Academy of Sciences, Beijing 100101, China Typescript received 5 April 2019; accepted in revised form 13 November 2019 Abstract: Fusuline faunas including 29 species belonging to 19 genera/subgenera are described from the Thitsipin For- mation in eight sections/localities on the Shan Plateau in eastern Myanmar. These fusulines broadly indicate a Midian (middle Permian, Guadalupian) age. The lower diversity and the presence of some genera, such as Monodiexodina and Eopolydiexodina, suggest that the Sibumasu Block belonged to the palaeobiogeographic Cimmerian Province during the Midian. Furthermore, quantitative cluster analysis of middle Permian fusulines from the Shan Plateau and adjacent Cim- merian blocks suggests close faunal affinities between the Sibumasu Block and the Baoshan Block in western Yunnan. More importantly, the widespread occurrence of fusulines Eopolydiexodina afghanensis and Jinzhangia shengi on the Shan Plateau is similar to that of contemporaneous fusuline faunas from the Baoshan Block and the South Qiangtang Block but different to that of the Tengchong and Lhasa Blocks, which are dominated by the characteristic Nank- inella–Chusenella assemblage. This faunal discrepancy pro- vides strong evidence that the Bangong–Nujiang suture passes through the Gaoligong Orogen in western Yunnan rather than through the Myitkyina ophiolites in northern Myanmar. Additionally, palaeobiogeographical analysis of these fusuline faunas from the Lhasa, Tengchong, South Qiangtang, Baoshan and Sibumasu Blocks implies that the Bangong–Nujiang Ocean might have been present before the Midian. Key words: fusulines, Myanmar, middle Permian, Sibu- masu Block, Tethys, palaeogeography. T HE Cimmerian continent consisted of a long string of blocks that rifted and drifted away from Gondwana dur- ing the Permian, such as the Central Iran, South Qiang- tang, Baoshan and Sibumasu Blocks (Seng€ or 1979; Stampfli & Borel 2002). The rifting of the Cimmerian continent resulted in the narrowing of the Palaeotethys Ocean in the north and the widening of the Neotethys Ocean or Mesotethys Ocean in the south (Zhang et al. 2013). However, the precise rifting history of these blocks and the opening times of many ancient oceans (e.g. the Bangong–Nujiang Ocean, the Neotethys Ocean) have been the subject of vigorous debate. For example, several different opinions have been expressed about the opening time of the Bangong–Nujiang Ocean. One suggestion is that it was a narrow ocean that opened in the Triassic or later (Kapp et al. 2003; Baxter et al. 2009). Another is that it was a vast ocean beginning as early as the Cam- brian (Pan et al. 2012). Moreover, some scholars favoured an opening time in the Permian based on some recent studies in geochemistry and palaeobiogeography (Zhang et al. 2016, 2019; Chen et al. 2017; Qiao et al. 2019). In addition to the discrepancies in the opening time for the Bangong–Nujiang Ocean, the southern extension of the Bangong–Nujiang suture zone in Myanmar has not been solved. For example, a cryptic suture zone (Paung Laung–Mawchi zone) in Myanmar separating the Irra- waddy Block (or the Mergui Group/slate belt) in the west and the Sibumasu Block in the east has been considered © The Palaeontological Association doi: 10.1002/spp2.1298 1 [Papers in Palaeontology, 2020, pp. 1–35]