Late Palaeozoic and Mesozoic Continental Ecosystems of SE Asia: an Introduction
Total Page:16
File Type:pdf, Size:1020Kb
Downloaded from http://sp.lyellcollection.org/ by guest on September 24, 2021 Late Palaeozoic and Mesozoic continental ecosystems of SE Asia: an introduction ERIC BUFFETAUT1*, GILLES CUNY2, JEAN LE LOEUFF3 & VARAVUDH SUTEETHORN4 1Centre National de la Recherche Scientifique, UMR 8538, Laboratoire de Ge´ologie de l’Ecole Normale Supe´rieure, 24 rue Lhomond, 75231 Paris Cedex 05, France 2Natural History Museum of Denmark, University of Copenhagen, Øster Voldgade 5–7, 1350 Copenhagen K, Denmark 3Muse´e des Dinosaures, 11260 Espe´raza, France 4Bureau of Fossil Research and Museums, Department of Mineral Resources, Rama VI Road, Bangkok 10400, Thailand *Corresponding author (e-mail: [email protected]) The papers in this volume concentrate on the ores and other useful substances. Although a large terminal Palaeozoic and Mesozoic non-marine for- part of its work also was of an economic nature, mations of Thailand and Laos. Similar formations the Hanoi-based Service ge´ologique de l’Indochine, are also known from other countries in mainland founded in 1894 (following the Service des Mines SE Asia, such as Malaysia (where several non- de la Cochinchine, 1868, and the Service des marine plant-bearing formations of Jurassic to Mines de l’Indochine, 1884), conducted research Cretaceous age are known: Lee et al. 2004), of a more academic nature, which led to important Vietnam and Cambodia (where red beds similar to palaeontological discoveries. In the course of geo- those of the Khorat Group of Thailand are wide- logical mapping in southern Laos in the late 1920s spread: Workman 1977; Fontaine & Workman and early 1930s, Hoffet thus found fossil bones 1978). However, the non-marine Late Palaeozoic and wood at several localities in the Mesozoic red and Mesozoic fossils of Thailand and Laos have beds of that area (Hoffet 1933). Hoffet’s major received much more attention than those of neigh- finds took place a few years later, when he discov- bouring countries, from which little has been ered fairly abundant Cretaceous dinosaur remains reported. What we know of the Late Palaeozoic near Muong Phalane, in southern Laos (Hoffet and Mesozoic ecosystems of SE Asia is therefore 1936, 1942, 1944; see also Buffetaut 1991). After very largely based on the Thai and Lao records. Hoffet was killed by the Japanese in 1945, war con- The study of these Late Palaeozoic and Meso- ditions prevailed for decades in Laos, and it was not zoic non-marine assemblages began in the 1890s until the 1990s that a French–Lao group could when French geologists took part in expeditions to resume research at Muong Phalane (Allain et al. the Lao principalities that served both a scientific 1999). The vertebrate-bearing red beds (‘Gre`s and a political purpose (the latter being clearly pre- supe´rieurs’) of southern Laos are now considered dominant, as the more or less avowed aim was to a lateral equivalent of the Aptian Khok Kruat bring that area under French influence). Counillon’s Formation of Thailand (Buffetaut 1991). 1896 report of a dicynodont skull from the vicinity In Thailand, Ho¨gbom (1914) was among the first of Luang Prabang thus is a landmark in the history to mention the red sandstone series of the Khorat of vertebrate palaeontology in SE Asia (Counillon Plateau, which he thought was Triassic in age and 1896). In later decades, the palaeontological explor- considered as a ‘Gondwana Formation’. Lee ation of the Late Palaeozoic and Mesozoic non- (1927, p. 411), discussing these sandstones, noted marine formations proceeded in different ways in that ‘no fossils were found, with the exception of a the French Indochinese colonies and in independent few pieces of badly petrified wood and small Siam (later Thailand). Although the Thai Depart- broken fragments of bone’. It was only in the ment of Mineral Resources was established as 1950s that Thai and foreign geologists began early as 1891 by order of king Rama V, the explora- detailed studies of the stratigraphy of the non- tions it conducted long had a predominantly marine rocks of NE Thailand (see Sattayarak economic character and concentrated on gems, 1983, for a review). The thick pile of non-marine From:BUFFETAUT, E., CUNY, G., LE LOEUFF,J.&SUTEETHORN, V. (eds) Late Palaeozoic and Mesozoic Continental Ecosystems in SE Asia. The Geological Society, London, Special Publications, 315,1–5. DOI: 10.1144/SP315.1 0305-8719/09/$15.00 # The Geological Society of London 2009. Downloaded from http://sp.lyellcollection.org/ by guest on September 24, 2021 2 E. BUFFETAUT ET AL. Mesozoic sediments of the Khorat Plateau, long Phu Phan and Khok Kruat Formations. The Khorat thought to be Triassic in age, was subdivided into Group is unconformably overlain by the Cenoma- several formations, the age of which long remained nian evaporitic Maha Sarakham Formation, and uncertain (and to some extent still is). In the early unconformably overlies Late Triassic (to basal 1960s, detailed field investigations resulted in both Jurassic?) non-marine formations (in ascending an important paper on the detailed stratigraphy of stratigraphic order, the Huai Hin Lat and Nam the Khorat Group (Ward & Bunnag 1964) and in Phong Formations). Vertebrate remains, either as the first study of vertebrate remains from these body fossils or as ichnites, are known from all the formations, which had been sent to Japan for identi- formations of the Khorat Group, as currently fication. Isolated teeth of a spinosaurid dinosaur and defined, as well as from the underlying Triassic for- a crocodilian were erroneously identified as belong- mations. They include freshwater sharks (reviewed ing to an ichthyosaur and a plesiosaur of Jurassic age by Cuny et al. 2007), bony fishes (reviewed by by Kobayashi et al. (1963), which resulted in endur- Cavin et al. 2007), temnospondyl amphibians (Buf- ing misconceptions about both the depositional fetaut et al. 1994a), turtles (reviewed by Tong et al. environment (supposedly marine) and the age 2006 and in this volume), phytosaurs (Buffetaut & (supposedly Jurassic or older) of the Khorat Ingavat 1982), crocodilians (Lauprasert et al. Group. Starting in 1980, Thai–French joint projects 2007), pterosaurs (Buffetaut et al. 2003), dinosaurs led to the discovery of vertebrate assemblages from (reviewed by Buffetaut et al. 2006) and birds (Buf- various formations of the Khorat Plateau, which fetaut et al. 2005a). The record of Mesozoic non- indicated non-marine environments and ages marine vertebrates from Thailand is summarized ranging from Late Triassic to mid-Cretaceous (e.g. in Figure 1. Fossil invertebrates are also present in Buffetaut & Ingavat 1986). Although the continen- many of these formations, as are plant remains, tal character of all the formations included in the mostly in the form of fossil wood (Philippe et al. Khorat Group was rapidly accepted, many uncer- 2004). tainties remained concerning the exact age of Mesozoic non-marine formations are also wide- these formations, although in some cases fossil ver- spread in northern Thailand, but have yielded far tebrates provided useful information. In the 1990s, fewer fossils than in NE Thailand. The general suc- petroleum exploration in NE Thailand provided cession seems to be similar to that of the Khorat seismic and palynological data that were of consi- Plateau, and vertebrate remains, including dinosaur derable use for dating the non-marine formations bones (Buffetaut et al. 2006) have been found at a in that area (Racey et al. 1994, 1996) and led to a few localities. reconsideration of the definition and content of the The southern peninsula of Thailand, which tecto- Khorat Group, now thought to consist mainly of nically belongs to the Shan-Thai (or Sibumasu) Early Cretaceous (and probably terminal Jurassic) block (whereas the Khorat Plateau is part of the rocks, comprising, in ascending stratigraphic Indochina block), shows Mesozoic formations, order, the Phu Kradung, Phra Wihan, Sao Khua, deposited in environments ranging from marine to Fig. 1. Distribution of main groups of vertebrates in the non-marine formations of Thailand. The Indochina Block comprises NE Thailand (Khorat Plateau). The Sibumasu (or Shan-Thai) Block includes western and southern (peninsular) Thailand. Figure courtesy of L. Cavin (Muse´e d’Histoire Naturelle, Geneva). Downloaded from http://sp.lyellcollection.org/ by guest on September 24, 2021 INTRODUCTION 3 brackish and continental (Meesook et al. 2005), Tong et al. cover the turtle record for the same which are not easily correlated with those of time interval, which suggests that SE Asia may NE Thailand. Both plant and animal remains have played an important part in the diversification are known from some of these formations. The of the Trionychoidea. This is illustrated by a second Khlong Min Formation, which is probably Middle paper by Tong et al., describing a new large crypto- to Late Jurassic in age, has yielded a diverse ver- diran turtle from the Phu Kradung Formation as a tebrate assemblage (Buffetaut et al. 1994b) includ- basal member of the Trionychoidea. Lauprasert ing sharks, bony fishes, temnospondyl amphibians, et al. describe a new slender-snouted neosuchian turtles, crocodiles and dinosaurs (Buffetaut et al. crocodyliform from the Khok Kruat Formation, 2005b). It also contains plant remains, including representing the youngest and most advanced Meso- amber (Philippe et al. 2005). zoic crocodyliform known from Thailand. Sutee- The papers in this volume deal with various thorn et al. describe the most complete skeleton aspects of the geology and palaeontology of the ever found of the sauropod Phuwiangosaurus sir- Late Palaeozoic and Mesozoic non-marine deposits indhornae, a dinosaur that is abundantly represented of SE Asia. Metcalfe first provides an introduction in the Early Cretaceous Sao Khua Formation. Klein to the tectonic and palaeogeographical evolution et al. present the results of their histological investi- of that part of the world, during a period marked gations on bones of Phuwiangosaurus sirindhornae, by the northward drift and collision with mainland which allow them to reconstruct the growth pattern Asia of several terranes or ‘microcontinents’ with and life history of that dinosaur.