Bollettino della Società Paleontologica Italiana Modena, Novembre 1999 Conodo n t Mass Extinction an d Recovery from Permian-Triassic Boundary Beds in the Meishan Sections, Zhejiang, China Cheng-yuan WANG Nanjing Institute of Geology and Palaeontology Academia Sini ca KEYWORDS- Conodonts, Mass extinction, Recovery, Permian/Triassic, Meishan, China. ABSTRACT-A high-resolution biostratigraphy and fine taxonomy are the basis for the study ofmass extinction and recovery. The Meishan sections provide a good example. Conodonts are commonly considered to be a leading fossi l group for the Permian and Triassic biostratigraphy. Conodonts of the Meishan sections have been studied extensively and ranges of alt conodont species are clear. Clarkina subcarinata (Sweet) disappears at the top ofthe Changhsing Limestone; Clarkina deflecta (\Vtlng & W'tzng) and C. xiangxiensis (Tian) disappear within boundary bed 2 (or bed 26); the range ofCiarkina meishanensis Kozur & W'tzng is confined to boundary bed l {or bed 25,26); Clarkina carinata (Clark) appears somewhat earlier than Hindeodus parvus (Kozur & Pjatakova); Clarkina changxingensis (\Vtlng & W'tzn.V extends up across the !ioundary and disappears in the u?Aer part of boundary bed 2; Hindeodus parvus, which evolved from Hindeodus fatidentatus praeparvus Kozur, appears first in the middle o boundary bed 2; Isarcicella staeschei Dai & Zhang appears in bed 28, 8 cm higher than Hindeodus parvus. The Meishan sections contain bot the pelagic facies conodont Clarkina and the neritic jacies conodont Hindeodus. After a detailed study of conodonts fr_om the Meishan sections, the present author that conodont mass extiction demonstrates a stepwise character, it was nota "sharp knife cut': Compared with other fossi! groups such as jusulinids and ammonoids, conodonts were the latest to become extinct in the P/T mass extinction. Duration of the conodont mass extinction is the shortest; and they were the earliest to recover as indicated by the FAD ofHindeodus parvus or the first appearence ofisarcicella staeschei. There were no conodont refogia or Lazarus taxa during the P/T mass extinction and recovery intervals. élarkina carinaça and Hindeodus latidentatus (Kozur, Mostler & Rahimi-Yazd) were crisis projenitor species; Hindeodus changxingensis C. Y.W'tzng and Clarkina meishanensis Kozur & W'tzng were disaster species or fai led crisis progenitor taxa. RIASSUNTO- [Estinzione di massa e radiazione dei conodonti attorno al limite Permiano/Triassico nella sezione di Meishan, Zhejiang, Cina] - La possibilità di disporre di dati biostratigrafici e tassonomici molto accurati sta alla base dello studio di un'estinzione di massa e della successiva radiazione. La sezione di Meishan ne costituisce un ottimo esempio. I conodonti sono considerati il più importante gruppo di fossili per la biostratigrafia del Permiano e del Triassico. Nella sezione di Meishan la fauna a conodonti è stata studiata in dettaglio e fa distribuzione stratigrafica di tutte le specie è stata determinata accuratamente. Clarkina subcarinata (Sweet) scompare al tetto del Changhsing Limestone; Clarkina deflecta (\Vtlng & W'tzng) e C. xiangxiensis (Tian) scompaiono all'interno del "boundary bed 2" (o livello 26); la distribuzione di Clarkina meishanensis Kozur & W'tzng è limitata al "boundary bed l" (o livello 25, 26); Clarkina carinata (Clark) compare appena prima di Hindeodus parvus (Kozur & Pjatakova); Clarkina changxingensis (\Vtlng & W'tzng) oltrepassa il limite e scompare nella parte alta del "bounda7, bed 2"; Hindeodus parvus, che si è evoluto da Hindeodus latidentatus praeparvus Kozur, compare nella parte mediana del "boundary bed 2 :· Isarcicella staeschei Dai & Zhang compare nel livello 28, 8 cm al di sopra di Hindeodus parvus. Nella sezione di Meishan sono presenti conodonti sia della facies pelagica a Clarkina, sia di quella neritica a Hindeodus. Lo studio dettagliato dei conodonti della sezione di Meishan dimostra come l'estinzione dei conodonti sia avvenuta a più riprese e non sia stata improvvisa. In con}ronto ad altri gruppi, come le fusuline e le ammoniti, i conodonti sono stati gli ultimi a scomparire e la durata della loro estinzione è stata la più breve: infatti, essi sono stati i primi a comparire, come testimoniano il FAD di Hindeodus parvus e la prima comparsa di Isarcicella staeschei. Durante l'estinzione di massa P/T non sono segnalate ne' aree di rifogio di conodonti, ne' taxa Lazzaro. Clarkina carinata andHindeodus latidentatus (Kozur et al.) possono essere considerate "crisis projenitor specie/; mentre Hindeodus changxingensis C. Y.W'tzng and Clarkina meishanensis Kozur & W'tzng potrebbero essere state "disaster species" o "jaifed crisis progenitor taxa': INTRODUCTION of mass extinction and recovery: l. The study of biotic recovery lays particular The mass extinction that occurred in the latest emphasis on benthic fauna in shallow water facies, Permian was the most extensive of the "five big events" particularly on reefs, corals, gastropods, brachiopods, in the Phanerozoic (Raup & Sepkoski, 1982). Nearly only a few papers deal with the pelagic fauna. 85% of marine species and some 70% of the terrestrial 2. Most palentologists understand that a high- vertebrate genera became extinct (Erwin 1994; resolution biostratigraphy and a fine taxonomy are Bowring et al., 1998). The Palaeozoic Evolutionary required for the study of mass extinction and recovery. Fauna of Sepkoski ( 1991) nearly vanished. Study of P l Bur these studies at present are mainly around the T mass extinction events was the focus of the study of generalized models of mass extinction and recovery Phanerozoic events in the eighties. Study of the biotic proposed by Kauffman & Erwin (1995) in which recovery from the P /T mass extinction is o ne of the recovery time intervals are qui te different. The shortest more important topics in the nineties. At present, the interval is 2-3 Ma (i. e., the recovery of pelagic following facts should be noted concerning the study graptolites in the early Silurian); the longest is l O 490 C.Y WANG (i. e., the biotic recovery of the Triassic). These time conduded definitely tbat the boundary day beds were intervals are too long to provide a high-resolution formed by volcanism an d contain very low iridum. This biostratigraphy. Extinction patterns of diffrent fossi! condusion was accepted by Rui et al. (1988) and Yin groups have been compiled from taxa ranges, often with et al. (1992) who added more evidences for the volcanic poor chronostratigraphic contro!. origin of the boundary day beds. Huge explosive volcanic eruptions in tbe eastern Tetbys and eruption The present author has selected conodonts of the of the Siberian Trap (Renne et al., 1995) lead to a drastic P/T boundary beds as a target for the study of the P/ drop in the biodiversity. The black day bed (the upper T mass extinction and recovery, primarily for the part of tbe boundary bed l or bed 26) represents a foliowing reasons: anoxia event. l. Conodonts are the leading fossi! group for Permian 3. The age of tbe boundary day beds (boundary bed l, and Triassic biostratigraphy, especialiy in recent years, or mixed bed l of Sheng et al., 1984) has been solved. and conodonts of the P/T boundary beds have been He (1981) first recognized rbat minerals of tbe intensively studied. these studies provide the basis for boundary day beds were similar to tbose of tbe day an excelient high-revolution biostratigraphy. beds witbin the Changhsing Limestone, but she stili 2. Conodont animals were nektonic, and the study of placed the P/T boundary at the base of tbe boundary their mass extinction and recovery should reveal a day beds. Zhang (1984) assigned the bed 26 (black concrete regular pattern in the pelagic facies. day) to the Yinkeng Formation and bed 25 (white 3. Idealiy, studies of mass extinction and recovery are day) to tbe Cbanghsing Formation. Clark et al. (1986) best made at the species leve!. Unfortunately most first put the boundary day beds to the Changbsingian current studies are limited to the generic or familial based on study of tbe conodonts from rbe day beds. levels. Thus the species-level record of conodonts in Sbeng et al. (1987) and Yin et al. (1996) also conduded the P/T boundary beds in the Meishan sections can tbat tbe age of the boundary day beds is provide a good example. Changbsingian. 4. As many as 13 definitions proposed for tbe P/T biostratigraphic boundary have been proposed. Tbese FOUNDAMENTAL DATA FOR THIS STUDY are summarized by Wang (1994). One of main proposals is to piace the base of the Triassic at the base Tbe stratigrapby and tbe conodonts of tbe P/T of the boundary day beds (Zbao, 1981; Sbeng et al., boundary beds of tbe Meisban sections bave been l984;Yangetal., 1987;Yin, 1994;Mei, 1996).Thus intensively studied in recent years (Wang, 1994, 1995, 1996; Wang et al., 1996; Wang &Wang, 1997; Kozur eta!, 1996;Mei, l996;Zhangetal., 1995).Although Be d there are stili some differences of opinion concerning Sample thickness number taxonomy,ranges, lineages and zonation of the (cm) conodonts (Wang, 1998), scientists are in generai "O Q) 884 D agreement, so the section provides a good basis for a 2:- Claraia wangi study of tbe P /T mass extinction an d recovery. ro _gJ Ophiceras è: Q) c Cl l. Tbe P /T boundary beds in the Meisban sections 2 ::J .!: o 883 (lJ c\'l are tbe continuous marine deposits. Tbe sedimentary è:' c: o (!) U5 environments was low slope facies. Wang (1994) 882-4 o C/) >o (.) "' <( stressed that tbe boundary day beds were the deposits (!) Biostratigraphic 882·3 LJ._ .:g 0:: below tbe storm wave base and the majority of tbe 0:: boundary H. parvus O> 0 l- C-- Q) numbers of the PTWG now accept tbis condusion ro 882-2 z (Wang et al., 1996; Kozur eta!., 1996; Yin eta!., 1996). è: :;:g><C 2 882-1 ii5 The opinion proposed byTozer (1986, 1988); Sheng .!: g> 0:: ro ·;;; UJ eta!.