A biogeographically mixed late Guadalupian (late Middle Permian) brachiopod fauna from an exotic limestone block at Xiukang in Lhaze county, Tibet Shuzhong Shen a, * , Sun Dongli a , G.R. Shi b a Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, 39 East Beijing Road, Nanjing 210008, People’s Republic of China b School of Ecology and Environment, Deakin University, Melbourne Campus, 221 Burwood Highway, Burwood, Vic. 3125, Australia Received 23 May 2002; accepted 6 November 2002 Abstract A total of 17 brachiopod species belonging to 15 genera are recorded from a limestone block of about 3 £ 4 km 2 in the Indus – Tsangbo suture zone at Xiukang in Lhaze County of Tibet. The brachiopod fauna generally indicates a Late Guadalupian age (late Wordian – Capitanian, late Middle Permian) based on its association with the Timorites-bearing ammonoid fauna and the presence of the brachiopod Urushtenoidea crenulata. Palaeobiogeographically, the fauna exhibits transitional/mixed characters between the warm-water Cathaysian and cold to temperate Gondwanan faunas and may have developed on a carbonate build-up or seamount on the oceanic crust. q 2003 Elsevier Ltd. All rights reserved. Keywords: Brachiopods; Exotic block; Tibet; Late Guadalupian; Permian 1. Introduction The Indus – Tsangbo suture zone in southern Tibet that marks the collision between the Indian subcontinent and Tibet is characterized by many geological features, including well-preserved ophiolitic suites, me ´lange, fore- arc turbidite sequences, large batholithos, molasse depos- its, as well as intensive structural deformations and metamorphism (Wang et al., 1996). Within the me ´lange, there exist numerous isolated Permian limestone blocks in fine clastic and/or volcaniclastic sediments of varying Mesozoic ages. Due to differential weathering, the lime- stone blocks typically protrude out from the surrounding matrix rocks and as a result form spectacular limestone hills (Fig. 1). Because of their peculiar field occurrences with the matrix rocks, these limestone blocks have been regarded by many as ‘exotic’, meaning that they have been displaced to their current positions by tectonic forces (e.g. Yin and Guo, 1975; Colchen et al., 1980; Robertson, 1998). Other theories have also been put forth in that these limestones were interpreted either as remnants of sea- mounts of the Neotethys (Wang and Mu, 1980), or fragments of an originally integrated carbonate platform that was situated on the northern fringes of Gondwanaland (Bassoullet et al., 1978; Jin, 1985; Guo et al., 1991). Despite the ubiquity of the limestone blocks and their prominence on the landscape within the suture zone, little is known about their internal stratigraphy, faunas and their depositional settings. Many of these limestone blocks are known to contain abundant macro-faunas (see faunal lists in Yin, 1997), but most of these faunas have never been studied in detail. Brachiopods are particularly abundant in these limestones and have been dealt with systematically only by Diener (1897). In the present paper, we will describe a brachiopod fauna collected by one of the authors (SDL) from a limestone block of about 3 £ 4 km 2 at Xiukang in Lhaze County of Tibet and discuss its age and palaeobiogeographical implications. This paper, coupled with our another study (Shen et al., 2003) on a brachiopod fauna from another small limestone block near Zhongbei in the same area, suggests that these limestone blocks may have been derived from a carbonate sequence developed on a carbonate build-up or seamount with 1367-9120/03/$ - see front matter q 2003 Elsevier Ltd. All rights reserved. doi:10.1016/S1367-9120(02)00187-6 Journal of Asian Earth Sciences 21 (2003) 1125–1137 www.elsevier.com/locate/jseaes * Corresponding author. Tel./fax: þ 86-25-3282131. E-mail addresses: szshen@nigpas.ac.cn (S.Z. Shen), grshi@deakin. edu.au (G.R. Shi).