Journal of Asian Earth Sciences 118 (2016) 101–110 Contents lists available at ScienceDirect Journal of Asian Earth Sciences journal homepage: www.elsevier.com/locate/jseaes Integrated biochronology for Triassic marine vertebrate faunas of Guizhou Province, South China ⇑ Zuoyu Sun a,b, , Dayong Jiang a, Cheng Ji c, Weicheng Hao a a Laboratory of Orogenic Belt and Crustal Evolution, Ministry of Education, and Department of Geology and Geological Museum, Peking University, Yiheyuan Street 5, Beijing 100871, PR China b State Key Laboratory of Palaeobiology and Stratigraphy (Nanjing Institute of Geology and Palaeontology, Chinese Academy of Science), Nanjing 210008, PR China c Key Laboratory of Economic Stratigraphy and Palaeogeography, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, PR China article info abstract Article history: The Middle and Upper Triassic marine deposits of Guizhou Province, which yielded exceptionally well- Received 10 November 2015 preserved vertebrate faunas, are further investigated. New age-diagnostic conodonts and ammonoids Received in revised form 28 December 2015 from six measured sections, together with already published data, allow us to construct an integrated Accepted 5 January 2016 biochronology straddling strata from the upper Guanling Formation (Anisian, Middle Triassic) to the Available online 6 January 2016 basal Xiaowa Formation (Carnian, Upper Triassic). Age constrains for those fossil Lagerstätten are now dated to the substage and zone levels: the Panxian Fauna, within the conodont Nicoraella kockeli Zone Keywords: and broadly coexisted with the ammonoid ‘Schreyerites’ binodosus, is suggested as latest Pelsonian (mid- Biochronology dle Anisian) in age; the Xingyi Fauna is assumed to be not younger than the middle Longobardian (Late Marine vertebrate faunas Triassic Ladinian) because the conodont Paragondolella inclinata with free-blade and the ammonoid Haoceras Guizhou Province xingyiensis are recorded from slightly younger strata; the conodont Paragondolella auriformis and the South China ammonoid Trachyceras multituberculatum and Austrotrachyceras triadicum clearly indicate that the Guanling Fauna is not older than Julian (early Carnian) in age (time interval between Aon Zone or Aonoides Zone). With the new biostratigraphic data, a relative sequence and correlation of the Middle Triassic vertebrate faunas from Guizhou (South China) and Monte San Giorgio (Southern Alps, Switzerland/Italy) is proposed. Ó 2016 Elsevier Ltd. All rights reserved. 1. Introduction Xiaowa Formation, near Xinpu of Guanling County. The Panxian Fauna appeared in publication slightly later (Wang et al., 2001), The Middle and Upper Triassic marine deposits of Guizhou Pro- and came from the Guanling Formation (Anisian, Middle Triassic) vinces, South China, have traditionally yielded fossil fishes and rep- near Xinmin of Panxian County. Many new finds of reptiles tiles (Young, 1958, 1965a, 1965b; Su, 1959). However, these (referred to as ‘China’s good-luck monsters’ by the National Geo- isolated materials with ambiguous provenance (localities and/or graphic Magazine) from these Lagersttätten have attracted stratigraphies) drew little attention of the scientific community increased attention from both scientists and the public. Many until the end of the last century (Lin and Rieppel, 1998; Rieppel, research groups, from China and overseas, have carried out exten- 1998, 1999, 2000). The boom was fueled by the discoveries and rel- sive studies and produced numerous publications that greatly evant researches of two new Lagerstätten with exceptionally pre- enhanced our knowledge of taxonomy, systematics, evolution served vertebrate fossils (i.e., the Anisian Panxian Fauna and the and paleobiogeography of these ‘sea monsters’ (Benton et al., Carnian Guanling Fauna), besides the already known Ladinian/ 2013 and references therein). Meanwhile, relevant fundamental early Carnian Xingyi Fauna that is famous for the pachypleurosaur work concerning their age determination, faunal composition, sed- Keichousaurus (Fig. 1a and b). Among the above three, the Guanling imentology and taphonomy have also been improved (Wang et al., Fauna was first discovered in 1999 (Li, 1999; Liu, 1999) in the 2008 and references therein; Motani et al., 2008; Jiang et al., 2009; Zou et al., 2015). Age determinations of those reptile Lagerstätten dated back to ⇑ Corresponding author at: Laboratory of Orogenic Belt and Crustal Evolution, 1958 when C.C. Young considered Keichousaurus hui as Ladinian Ministry of Education, and Department of Geology and Geological Museum, Peking (Middle Triassic) in age based on its evolution level among the University, Yiheyuan Street 5, Beijing 100871, PR China. Pachypleurosauria (Young, 1958). Wang et al. (1998), on the basis E-mail address: [email protected] (Z. Sun). http://dx.doi.org/10.1016/j.jseaes.2016.01.004 1367-9120/Ó 2016 Elsevier Ltd. All rights reserved. 102 Z. Sun et al. / Journal of Asian Earth Sciences 118 (2016) 101–110 Fig. 1. (a) Geographic map and (b) Simplified lithostratigraphic log of the Triassic marine vertebrate faunas in Guizhou Province, South China and its adjacent area; (c–e) showing the localization of measured sections. (1) Zhuganpo section, Yongningzhen, Guanling County, Guizhou Province (GLZ); (2) Xiaowa section, Xinpu, Guanling County, Guizhou Province (GLX); (3) Yangjuan-Chupiwa section, Xinmin, Panxian County, Guizhou Province (YC); (4) Zhachong section, Changdi, Luoping County, Yunnan Province (LPZ); (5) Shijiangjun section, Banqiao, Luoping County, Yunnan Province (LPS); (6) Niubudai section, Banqiao, Luoping County, Yunnan Province (LPN). of the presence of the conodont Paragondolella polygnathiformis establish an integrated biochronology that extends across the Tri- 3 m above the Keichousaurus bed of the type locality, assigned assic marine vertebrate faunas mentioned above. Such an inte- the Xingyi Fauna as early Carnian, rather than late Ladinian as pro- grated biochronology is in part calibrated with the relevant data posed in earlier work (Young, 1958, 1965a; Su, 1959; Dong, 1980). from the Middle Triassic succession of Monte San Giorgio (South- However, complex tectonic condition around the type locality of ern Alps, Switzerland/Italy) (Stockar et al., 2012) and also GSSPs the Xingyi Fauna makes Wang et al. (1998)’s conclusion question- of the Ladinian and Carnian (Brack et al., 2005; Mietto et al., able. The ammonoid biostratigraphy of the laterally equivalent sec- 2012). Thus, the Triassic marine vertebrate Lagerstätten of Guizhou tions that do not yield fossiliferous layers (Wang, 1983; Xu et al., Province are now dated to the substage and zone levels and are 2003) suggested an early-middle late Ladinian age and was preliminarily correlated to analogous faunas of Monte San Giorgio. recently in part confirmed by ammonoids directly collected during Meanwhile, their stratigraphy and fauna composition is also a large scale yet bed-by-bed excavation of the fossiliferous layers improved following Benton et al. (2013) and Tintori et al. (2014) (Zou et al., 2015). Meanwhile, a rather broad age assignment of with new data from the joint excavations held by Peking Univer- the Xingyi fauna to the Ladinian–Carnian is still held by some sity, Beijing, University of California, Davis, USA, and Università researchers (Benton et al., 2013), which to some extent blurs the degli Studi di Milano, Italy during 2004–2014. age difference between the Xingyi Fauna and the younger Guanling Fauna. The Guanling Fauna in the basal Xiao Formation was corre- lated to lower Carnian (Upper Triassic) based on cephalopods (Hao 2. Palaeogeographical setting et al., 2003; Xu et al., 2003) or middle Carnian (Upper Triassic) based on conodonts (Wang, 2000; Chen and Wang, 2002; Sun During the Triassic Period the southwestern corner of Guizhou et al., 2003) and ichthyoliths (Chen and Cuny, 2003). Sun et al. Province (i.e., the study area in the present paper) was located at (2006, 2014) presented conodont biostratigraphic data from the the south-west platform margin of the Yangtze Platform between upper Guanling Formation near the type locality of the Panxian the Khamdian (Kangdian) Old Land and the Nanpanjiang Basin Fauna and referred it to the conodont Nicoraella kockeli Zone, indi- (also named the Youjiang depression in some Chinese references). cating a Pelsonian (Middle Anisian) age. The Yangtze Platform almost extended across the entire Yangtze Herein, we integrate new conodont and ammonoid data from plate (west from the present South China Sea to the Longmen Shan, six measured sections, together with already published data, to north from near the Vietnamese border, and beyond the valley of Z. Sun et al. / Journal of Asian Earth Sciences 118 (2016) 101–110 103 the Yangtze River) and the Nanpanjiang Basin developed in the layers, equal to beds 77–91 of Motani et al. (2008) and Cy 10–13 of border region between Yunnan, Guizhou and Guangxi provinces Sun et al. (2006), are a ca. 2 m thick interval of dark gray to black and adjacent areas in northern Vietnam (see Fig. 1 in Enos et al., laminated lime or dolomitic mudstones with rich organic matters 1998). As a stable palaeogeographic element from the Late Protero- and at least five bentonite layers of variable thickness. Vertically, zoic to Middle Triassic the Yangtze Platform was characterized by eight vertebrate-bearing beds (Motani et al., 2008) are identified shallow-water carbonate deposits, whereas the Nanpanjiang