Early Triassic conodont–palynological biostratigraphy of the Meishan D Section in Changxing, Zhejiang Province, South China

Palaeogeography, Palaeoclimatology, Palaeoecology 252 (2007) 4 – 23 www.elsevier.com/locate/palaeo

Early Triassic conodont–palynological biostratigraphy of the Meishan D Section in Changxing, Zhejiang Province, South China Kexin Zhang a,⁎, Jinnan Tong a , G.R. Shi a,b , Xulong Lai a , Jianxin Yu a,c , Weihong He a , Yuanqiao Peng a,b , Yali Jin a a

b

GPMR and BGEG Laboratories at China University of Geosciences, Wuhan 430074, Hubei, PR China School of Ecology and Environment, Deakin University, Melbourne Campus, 221 Burwood Highway, Burwood, VIC 3125, Australia c Laboratory of Paleobotany and Paleoecology, University Piere et Marie Curie, 75005 Paris, France Accepted 30 November 2006

Abstract The Lower Triassic, consisting of the Yinkeng Fm., Helongshan Fm. and the lower part of the Nanlinghu Fm., is well developed at the Meishan D Section of Changxing County, Zhejiang Province, South China. Based on detailed study of the conodont biostratigraphy from the interval of the Permian–Triassic boundary and the Lower Triassic in the Meishan D Section, 8 conodont zones are recognized in ascending order as follows: the Neogondolella changxingensis yini–Hindeodus praeparvus Zone (beds 24a–24e, top of the Changxing Fm.), the Neogondolella meishanensis meishanensis–Hindeodus eurypyge Zone (beds 25–27b, base of the Yinkeng Fm.), the Hindeodus parvus Zone (beds 27c–27d, first conodont zone of Triassic, the global index for the base of Triassic), the Isarcicella staeschei Zone (beds 28–29a, lower part of the Yinkeng Fm), I. isarcica Zone (beds 29b–51, lower part of the Yinkeng Fm.), the Neogondolella tulongensis–N planata Zone (beds 52–72, from upper part of the Yinkeng Fm. to lower part of the Helongshan Fm.), the Neospathodus kummeli Zone (beds 73–92, middle part of the Helongshan Fm.), and the Neospathodus cristagalli–N dieneri Zone (beds 93–111, from upper part of the Helongshan Fm. to the base of the Nanlinghu Fm.). At the Meishan D Section, the palynological biostratigraphy is also studied herein. The palynological assemblage of Lundbladispora–Taeniaesporites–Equisetosporites is found in the intervals which contain the conodont Isarcicella isarcica Zone and the lower part of the Neogondolella tulongensis–N. planata Zone. © 2007 Elsevier B.V. All rights reserved. Keywords: Lower Triassic; Conodont; Palynomorph; Biostratigraphy; Meishan Section; South China

1. Introduction The Meishan D Section is located on the south hillside along the road from the town of Meishan to ⁎ Corresponding author. Tel./fax: +86 27 67885047. E-mail address: [email protected] (K. Zhang). 0031-0182/$ - see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.palaeo.2006.11.031

Xinhui Village, Changxing County, Zhejiang Province (Yin et al., 2001). This section has been ratified as the Global Stratotype Section and Point (GSSP) of the Permian–Triassic boundary (PTB) (Yin et al., 2001). The conodont biostratigraphy of the interval from the Upper Permian Changhsingian to the PTB (the lower Yinkeng Formation) at this section has been extensively

K. Zhang et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 252 (2007) 4–23

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Fig. 1. Distribution of conodont and palynomorph fossils in the Permian–Triassic Boundary interval and the Lower Triassic Yinkeng Fm. of the Meishan D Section, Changxing, Zhejiang, South China.

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K. Zhang et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 252 (2007) 4–23

Fig. 2. Distribution of conodont fossils from the Helongshan and Nanlinghu formations of the Lower Triassic in the Meishan D Section, Changxing, Zhejiang, South China.

K. Zhang et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 252 (2007) 4–23

studied (Zhang, 1984, 1987, 1988; Wang, 1994, 1995; Lai et al., 1995, 2001; Zhang et al., 1995, 1996; Ding et al., 1996; Nicoll et al., 2002; Mei et al., 1998). However, the Lower Triassic part of this section has received relatively little study due to poor access. Although Tong and Yang (1998) presented a brief report on the conodont zonation of the Lower Triassic of this section, the conodont biostratigraphy of the Lower Triassic Yinkeng (upper part), Helongshan and Nanlinghu formations remains far under-studied relative to that of the Late Permian Changxing Formation and the PTB sequence. In addition, the Early Triassic palynostratigraphic study of the Meishan D Section and its correlation with the conodont zones should also be strengthened because its correlation potential for the marine and non-marine PTBs is of global significance. Over the last few years, we have undertaken a systematic and detailed study of the Lower Triassic Yinkeng, Helongshan and Nanlinghu formations, indicating high-resolution bed by bed collections of conodont and palynomorph samples. This paper is a direct result of our recent efforts and aimed to provide basic palaeontological data toward refine the chronostratigraphical framework of the Lower Triassic. 2. Lithology of the uppermost Permian–Lower Triassic Meishan D Section The uppermost Permian–Lower Triassic of the Meishan D Section is composed of the Yinkeng Formation, Helongshan Formation and the lower part of the Nanlinghu Formation (Figs. 1 and 2). The Yinkeng Formation (Beds 25–60 at the Meishan D Section, Fig. 1), conformably overlies the Changxing Formation with a thickness of 14.10 m; it is mainly a succession of horizontally bedded calcareous mudrocks calculated with dark mudrocks rhythmically. The rocks contain abundant conodonts (Fig. 1, Table 1), the bivalves Claraia concentrica, C. dieneri, C. fukienenisis, C. griesbachi, C. lungyenensis, Pseudoclaraia wangi, and the ammonoids Ophiceras cf. subdemissum. The dark mudrocks are rich in organic matter and micrograins of pyrites, indicating the presences of the anoxic environment. This view is supported by the research of Permian–Triassic deposition in other areas (Wignall et al., 2005). The conodonts, bivalves and ammonoids indicate a deep-water environment (Zhang et al., 1997). Therefore, both lithology and biology suggest that the strata of Yinkeng Formation were deposited in a deep shelf environment in the study area. The Helongshan Fm (Fig. 2), conformably overlying on the Yinkeng Formation, is subdivided into two

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Members by lithology. The Lower Member (Beds 61– 84, Fig. 2) is composed of gray thin-bedded micrites, rarely intercalated with gray medium to thick-bedded micrites with horizontal to slightly wavy bedding, or, at the base, with yellowish green thin to extremely thin-bedded calcareous mudstone containing abundant conodonts (Fig. 2, Table 2). The thickness of the Lower Member is 72.75 m. The Upper Member (Beds 85–104, Fig. 2) contains abundant conodonts and consists of gray and yellowish gray medium to thinbedded micrites intercalated with gray thin-bedded argillaceous limestones, and rarely intercalated with gray to dark gray thick-bedded micrites and pink, thinbedded micrites with argillaceous bands. Brecciated limestones occur rarely in the upper part. It is in conformable contact with the underlying Lower Member of the Helongshan Formation and the overlying Nanlinghu Fm. The total thickness of the Upper Member is 106.77 m. It is interpreted to be formed in a background of transgression, as it is predominated by micrites in an open shallow shelf (Tong and Yin, 1998). The Nanlinghu Fm. (Beds105–111, Fig. 2) is considered to be formed with the gradual filling of a restricted to semi-restricted littoral — shallow basin in response to the continual regional falling of the sea level across South China in the late Early Triassic (Zhang et al., 2005). It is composed mainly of reddish gray and grayish white thick-bedded to massive micrites (Fig. 2), intercalated by grayish white, medium-bedded micrites, gray thick-bedded vermiform limestones and grayish white thick-bedded dolomitic micrites in the lower part, and by grayish white thick-bedded striped limestones (the term of striped limestone is referred to the alternation of gray and white in color and not a specific facies comprising alternating micrite and calcite), argillaceous striped limestones, pink thick-bedded calcirudites and grayish white massive micrites with karst holes in the middle and upper parts. Most beds are massive with horizontal bedding, rhythmic laminations and bioturbations. The Nanlinghu Formation is incomplete at the Meishan D Section, with it top part eroded (Zhang et al., 2005), and as such, in the Meishan area, about 44–60 m is preserved. 3. Conodont biostratigraphy 147 conodont samples were collected from Bed 24a to Bed 111 in the Meishan D Section, each weighing 3 kg; of these, 95 samples were productive. In total, 9 conodont genera and 40 species have been identified (Figs. 1 and 2; Tables 1 and 2). Based on the detailed

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Table 1 Statistic of conodont individuals of each species in each sample from the uppermost Changxing Formation and the lower Yinkeng Formation at the Meishan D Section Period

Bed no. N. changxingensis N. changxingensis N. deflecta N. predeflecta N. meishanensis N. parasubcarinata N. subcarinata yini changxingensis zhangi

Lower 50 Triassic 47 46 45 44 43 42 41 40 39 38 37 36 35 34 33 31 30 29b 29a 28 27d 27c Upper 27b Permian 27a 26 25 24e 24d 24c 24b 24a N. wangi

2 6 19 2 5 11

N. orientalis

1 2 1 3 2 17 115 49 25 61 N. meishanensis meishanensis

1 1 2 3 2 14 23 1 9 21 N. taylorae

(bed by bed) stratigraphic distribution of the conodonts from the top of the Changxing Formation (Beds 24a– 24e), Yinkeng Formation (Beds 25–60), Helongshan Formation (Beds 61–104) and Nanlinghu Formation (Beds105–111), 8 conodont zones can be well defined in ascending order (Figs. 1 and 2): 3.1. Neogondolella changxingensis yini–Hineodus praeparvus Zone This zone occurs in Beds 24a–24e, at the top part of the Changxing Formation (Fig. 1), it begins with the first occurrence of N. changxingensis yini (Mei) and ends with the first occurrence of N. meishanensis meishanensis (Zhang). Mei et al. (1998) first suggested a yini zone at the Meishan Section while Orchard and Krystyn (1998) proposed a praeparvus zone in Spiti. Perri and Farabegoli

1 21 5

9

3 1 2

3 4 N. carinata

15 N. planata

Hindeodus inflatus

H. lantidentatus

(2003) also reported a praeparvus zone at the Tesero and Bulla Sections in the Southern Alps (Italy). As such, we propose to use the Neogondolella changxingensis yini– Hineodus praeparvus Zone as the zonal name because they both first occurred together in the same interval. The fossils in this zone are of high diversity, containing 17 conodont species (Fig. 1). The common species in this zone are Neogondolella changxingensis yini (Mei), N. changxingensis changxingensis (Wang et Wang), N. deflecta (Wang et Wang), N. predeflecta (Mei), N. meishanensis zhangi (Mei), N. parasubcarinata (Mei), N. subcarinata (Sweet), N. wangi (Zhang), Hindeodus inflatus Nicoll, Metcalfe et Wang, H. lantidentatus (Kozur, Mostler et Rahimi-Yazd), H. praeparvus Kozur, H. typicalis (Sweet), Ellisonia dinodoides (Tatge), Enantiognathus ziegleri (Diebel), Lonchodina muelleri Tatge and Xaniognathus elongatus (Sweet). The other

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Table 1 (continued ) N. wangi

N. orientalis

N. meishanensis meishanensis

N. taylorae

N. carinata

N. planata

Hindeodus inflatus

H. lantidentatus

1 1 1 1 1

1 3 2

2

1 2 1 1 1

1

2 4 1 2 3

2

2

4 2

1 1 12 1 2

1 1 3 4 2

1 3

3 1 1 (continued on next page)

important fossils in this zone at the Meishan D Section include the ammonoid Rotodiscoceras sp. and the fusulininacean Palaeofusulina sp., belonging to the terminal Changhsingian (Figs. 3–5). 3.2. Neogondolella meishanensis meishanensis–Hindeodus eurypyge Zone This zone includes the “Boundary Clay Bed” (Beds 25–26, see Yin, 1985) and Beds 27a–27b (Fig. 1). Its lower limit is marked by the first occurrence of N. meishanensis meishanensis (Zhang) and H. eurypyge Nicoll, Metcalfe and Wang. The top of this zone is marked by the first appearance of Hindeodus parvus (Kozur and Pjatakova). The conodonts in this zone decrease somewhat in abundance but maintain high diversity, comprising 13 conodont species (Fig. 1). The

common species in this zone are Neogondolella changxingensis changxingensis (Wang et Wang), N. changxingensis yini (Mei), N. deflecta (Wang and Wang), N. orientalis (Barskov and Koroleva), N. subcarinata (Sweet), Hindeodus changxingensis Wang, H. eurypyge Nicoll, Metcalfe and Wang, H. inflatus Nicoll, Metcalfe et Wang, H. praeparvus Kozur, H. priscus Kozur, H. typicalis (Sweet), Ellisonia dinodoides (Tatge) and Xaniognathus elongatus Sweet. The Neogondolella species are commonly found in the “Boundary Clay Bed” (Beds 25–26), dominated by N. changxingensis (Wang and Wang), N. deflecta (Wang and Wang) and the newcomer N. meishanensis meishanensis (Zhang). Hindeodus species are common in the upper part of this zone (Beds 27a–27b), such as H. eurypyge Nicoll, Metcalfe and Wang, H. inflatus

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Table 1 (continued ) Period

H. praeparvus H. eurypyge H. changxingensis H. priscus H. parvus H. turgidus H. typicalis Isarcicella staeschei I. isarcica

Lower Triassic

1

1

1 2 1

2 1

2

1 2 4 1 1

1 9

1 1 1

3

1

3 1 1 1

1 2 1

2

1

3

1

1 29 4 3

1 7 3

1 1 2

5 4 2 Upper 2 Permian 4

5 2

1

3

2 1

5

15 1 2 1 1 1

1 1 2

2

1

2

Nicoll, Metcalfe and Wang, H. praeparvus Kozur, and H. typicalis (Sweet). In the Permian–Triassic Boundary sections in South China and elsewhere around the world, there is usually an interval of strata ranging from several centimeters to several meters below the first occurrence of the Hindeodus parvus Zone, which usually contains abundant representatives of 6-element species such as, notably, H. eurypyge Nicoll, Metcalfe and Wang and H. typicalis (Sweet). This is the so-called H. typicalis Fauna interval (Zhang et al., 1995; Yin et al., 2001), which typically contains only a few fossils with low abundance and low diversity. Lai et al. (2001) and Nicoll et al. (2002) discussed in detail the abrupt shift from a Neogondolella (Clarkina) fauna in the latest Permian to one dominated by Hindeodus and Isarcicella at or about the Permian–Triassic boundary level in some sections, including those at Meishan. The ammonoids Otoceras? sp. and Hypophiceras spp. have also been found in this zone (Sheng et al., 1984). These fossils were previously regarded as the earliest

24 1 4 2 3

1

19

2 3 5 3 7

Triassic forms but now are placed in the latest Permian according to Yin et al. (1988, 2001). Other fossils in this zone mostly comprise typical Late Permian forms, such as the ammonoid Pseudogastrioceras sp., the conodonts N. changxingensis, N. deflecta and many Permian-type brachiopods Crurithyris flabelliformis and Neowellerella pseudoutah (Yin et al., 2001). Yang et al. (1993) indicated that the Hypophiceras bed in Dalishan, Zhenjiang, Jiangsu Province, previously placed at the base of the Triassic, contains typical Permian conodonts, and thus corresponds to this conodont zone. The Neogondolella meishanensis meishanensis– Hindeodus eurypyge Zone corresponds to the “Mixed Bed 1” and the lower part of the “Mixed Bed 2” of Sheng et al. (1984), the “Lower Transitional Bed” and the lower part of the “Upper Transitional Bed” of Yin (1985), and the “Boundary Bed 1” and the “Lower Boundary Bed 2” proposed by Wang (1994) in the Meishan Z Section. The base of this zone, i.e. the base of Bed 25, is the lithostratigraphical boundary between

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Table 2 Statistic of conodont individuals of each species in each sample from the upper Yinkeng Formation, Helongshan Formation and Nanlinghu Formation at the Meishan D Section Period

Bed no.

111 Power Triassic 109 107 106 102 95 94 93 88 87 82 81 79 75 74 73 72 70 69 68 63 62 61 59 58 57 56 55 54 53 52 51 Period

Bed no.

H. eurypyge

Hindeodus inflatus

H. H. lantidentatus parvus

H. praeparvus

H. priscus

Isarcicella staeschei

I. isarcica

Neogondolella carinata

1

5 1 1 1 1 1 2 1 1 1 1 2 2 N. planata

N. meishanensis meishanensis

1

2 1

1 6 1

1

N. N. tulongensis discreta

the Changxing and Yinkeng formations; and its top, i.e. top of Bed 26, is the eventostratigraphical boundary as well as being the sequence stratigraphic transgressive surface (Yin and Tong, 1995; Zhang et al., 1995, 1997). 3.3. Hindeodus parvus Zone This zone includes Beds 27c and 27d (Fig. 2), beginning with the first appearance of the H. parvus (Kozur and Pjatakova). The upper limit of this zone is marked by the first occurrence of I. staeschei Dai and Zhang. In this zone, other associated forms include H. eurypyge Nicoll, Metcalfe and Wang, H. inflatus Nicoll, Metcalfe and Wang, H. lantidentatus (Kozur, Mostler et Rahimi-Yazd), H. praeparvus Kozur, H. priscus Kozur, H. turgidus (Kozur, Mostler et Rahimi-Yazd), H. typicalis (Sweet), Neogondolella

1 3

N. taylorae

Neospathodus N. sp. kummeli

2 page) N. (continuedN.on next N. cristagalli dieneri spathi

taylorae Orchard, Sc element of Ellisonia dinodoides (Tatge), and M element of Lonchodina mülleri (Tatge) (Fig. 1). This horizon is equivalent to the upper part of the “Mixed Bed 2” of Sheng et al. (1984), the upper part of the “Upper Transitional Bed” of Yin (1985) and the “Upper Boundary Bed 2” of Wang (1994) in the Meishan Z Section. Compared with the N. meishanensis meishanensis–H. eurypyge Zone (containing only the Permian-type fauna), the H. parvus Zone is characterized by mixed faunas of Triassic new-comers (e.g. H. parvus, H. turgidus, N. taylorae) and Permian relicts (e.g. Neogondolella changxingensis, H. eurypyge, H. inflatus, H. lantidentatus, etc.). The FAD of N. taylorae and H. parvus occur at the same horizon in the Meishan D Section in this study, as well as in the Selong section, south Tibet (Orchard et al., 1994; Mei, 1996). In Spiti, the FAD of N. taylorae is in the Hindeodus praeparvus Zone which is below the H. parvus Zone (Orchard and Krystyn, 1998); however,

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Table 2 (continued ) Period

Bed no.

Power 111 Triassic 109 107 106 102 95 94 93 88 87 82 81 79 75 74 73 72 70 69 68 63 62 61 59 58 57 56 55 54 53 52 51

N. planata

N. meishanensis meishanensis

N. N. tulongensis discreta

N. taylorae

Neospathodus N. sp. kummeli

6 2 4 1 2

N. N. cristagalli dieneri 1 2 4 2 1 3 2 1

N. spathi

1 1

3 1

1 1

1

1

3 1

2

2

3

3 1 1 2

1

1

2

1

1 2 5 3

2

1 2 2 3 5 3

1

3 4 2

1

Orchard and Krystyn (1998) assigned both the Hindeodus praeparvus and H. parvus zones to the basal Triassic. Well-known localities where the H. parvus Zone has been recognized include: Shangsi of Sichuan, Xishan of Tibet, Guryul Ravine of Kashmir, Spiti of India, Abadeh, Kuh-e-Ali Bashi and Dorasham of Iran, Narmal Nala of

Pakistan, Gartner Kofel of Austria, Tesero of Italy, western America, Arctic of Canada and Timor (Yin et al., 1988, 2001; Wang, 1994; Zhang et al., 1995, 1996; Nicoll et al., 2002; Perri and Farabegoli, 2003; Kozur, 2004). The world-wide distribution of Hindeodus parvus constitutes the basis for its FAD to be regarded as the global Triassic base (Yin et al., 1988, 2001).

Fig. 3. SEM photos of conodonts in the uppermost Permian–Lower Triassic strata of the Meishan D Section. All specimens are housed in the Faculty of Earth Sciences, China University of Geosciences, Wuhan, Hubei Province, P. R. China. All illustrations are Pa elements. All are lateral views, except 10 which is the upper view. 1: Hindeodus inflatus Nicoll, Metcalfe et Wang, 2002, from Bed 24a of Changxing Fm., ×140, MDP24a–006. 2, 16: Hindeodus praeparvus Kozur, 1996, 2 is from Bed 24c of Changxing Fm., ×120, MDP24c–012; 16 is from Bed 52 of Yinkeng Fm., ×100, MDT52-001. 3: Hindeodus latidentatus Kozur Mostler et Rahimiyazd, 1975, from Bed 27c of Yinkeng Fm., ×120, MDT-27c-007. 4, 5: Hindeodus eurypyge Nicoll, Metcalfe et Wang, 2002, 4 is from Bed 28 of Yinkeng Fm., ×70, MDT-28-003; 5 is from Bed 42 of Yinkeng Fm., ×120, MDT-42-4001. 6, 9, 12, 14, 15: Hindeodus parvus Kozur et Pjatakova, 1976, 6 is from Bed 27d of Yinkeng Fm, ×150, MDT-27d-007; 9 is from Bed 63 of Helongshan Fm, ×150, MDT-63-1-001; 12 is from Bed 54 of Yinkeng Fm, ×150, MDT-54-014; 14 is from Bed 35 of Yinkeng Fm, ×150, MDT-35001; 15 is from Bed 27c of Yinkeng Fm, ×100, MDT-27c-002. 7, 10: Isarcicella staeschei Dai et Zhang, 1989, 7 is from Bed 51 of Yinkeng Fm, ×120, MDT-51-3-001; 10 is from Bed 42 of Yinkeng Fm, ×120, MDT-42-4-003. 8: Hindeodus typicalis (Sweet, 1971), from Bed 24e of Changxing Fm, ×100, MDP-24e-019. 11: Isarcicella isarcica Huckriede, 1958, from Bed 51 of Yinkeng Fm, ×150, MDT-51-4-001. 13: Neospathodus kummeli Sweet, 1970, from Bed 93 of Helongshan Fm, ×130, MDT-93-001. 17, 18, 21: Neospathodus dieneri Sweet, 1970, 17 is from Bed 109 of Nanlinghu Fm, ×150, MDT-109-003; 18 is from Bed 95 of Helongshan Fm, ×150, MDT-95-1-002; 21 is from Bed 95 of Helongshan Fm, ×150, MDT-95-1-003. 19: Neospathodus cristagalli (Huckriede, 1958), from Bed 107 of Nanlinghu Fm, ×200, MDT-107-001. 20: Hindeodus sp, from Bed 68 of Helongshan Fm, ×150, MDT-68-2-001.

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3.4. Isarcicella staeschei Zone This zone includes Beds 28–29a (Fig. 1). The base of this zone is defined by the first appearance of I. staeschei Dai and Zhang while its top is marked by the first appearance of I. isarcia Huckriede. Hindeodus which bloomed in the next zone. Common species include Hindeodus changxingensis Wang, H. eurypyge Nicoll, Metcalfe et Wang, H. inflatus Nicoll, Metcalfe et Wang. H. lantidentatus (Kozur, Mostler et Rahimiyazd), H. parvus (Kozur et Pjatakova), H. turgidus (Kozur, Mostler et Rahimiyazd), H. typicalis (Sweet), Isarcicella staeschei Dai and Zhang, Neogondolella sp., M element of Lonchodina sp., Sb element of Ellisonia sp., Sc element of Ellisonia dinodoides (Tatge), Xaniognathodus elongates Sweet, Xaniognathodus elongatus Sweet. According to the data from the Tesero Section of Italy (Perri and Farabegoli, 2003), Xiaoba Section of Sichuan, China (Lai, 1997) and the Meishan Section (this paper), I. staeschei occurred earlier than I. isarcica. Wang (1996), Orchard and Krystyn (1998) and Perri and Farabegoli (2003) proposed to set up a staeschei Zone below the isarcica Zone. In this study, abundant elements of I. staeschei have been found in Beds 28 (Table 1). The Isarcicella staeschei Zone corresponds to the top part of “Mixed Bed 3” of Sheng et al. (1984), the top part of the “Upper Transitional Bed” of Yin (1985) and the base of “Boundary Bed 3” of Wang (1994) in the Meishan Z Section. 3.5. Isarcicella isarcica Zone This zone includes Beds 29b–51 (Fig. 1). In this zone, the lower limit is defined by the FAD of Isarcicella isarcica. The upper limit is marked by the disappearance of I. isarcica. Associated other forms include Hindeodus eurypyge Nicoll, Metcalfe et Wang, Hindeodus inflatus Nicoll, Metcalfe et Wang. H. latidentatus Kozur Mostler et Rahimiyazd, H. parvus

(Kozur et Pjatakova), H. praeparvus Kozur, H. priscus Kozur, H. turgidus (Kozur, Mostler et Rahimiyazd), H. typicalis (Sweet), Isarcicella isarcica Huckriede, Isarcicella ?lobata Perri et Farabegoli, I. staeschei Dai et Zhang, Neogondolella carinata (Clark), N. planata (Clark), N. tulongensis Tian, M element of Lonchodina. sp., Sb element of Ellisonia sp., Sc element of Ellisonia dinodoides (Tatge). The typical element Isarcicella isarcica is also found in bed 29b from the Meishan A Section. Above evidence suggests this zone starts at the bed 29b. This zone developed at many sections around the world including South China, Tibet, Pakistan, Kashmir, India, Iran, Italy, Western USA, Austria, Australia and Canada (Paull, 1982; Yin et al., 1988, 2001; Orchard et al., 1994; Zhang et al., 1995, 1996; Belka and Wiedmann, 1996; Nicoll et al., 2002; Perri and Farabegoli, 2003). 3.6. Neogondolella tulongensis–N. planata Zone This zone, of late Griesbachian age, includes Beds 52– 72 (Figs. 1 and 2). Its base is marked by the disappearance of I. isarcica (Huckriede) and the top is marked by the occurrence of Neospathodus kummeli Sweet. Common species are Neogondolella carinata (Clark), N. discreta Orchard et Krysty, N. meishanensis meishanensis (Zhang), N. planata (Clark), N. taylorae Orchard, N. tulongensis Tian, Neospathodus sp., Hindeodus eurypyge Nicoll, Metcalfe et Wang, H. inflatus Nicoll, Metcalfe et Wang, H. latidentatus (Kozur, Mostler et Rahimi-Yazd), H. parvus (Kozur et Pjatakova), H. praeparvus Kozur, H. priscus Kozur, H. typicalis (Sweet), M, Sa and Sc elements of Hadrodontina aequabilis Staesche, M elements of Lonchodina muelleri (Tatge), M elements of Lonchodina sp., M, Sa, Sb and Sc elements of Ellisonia dinodoides (Tatge), Sb and Sc elements of Ellisonia sp., and Xaniognathus elongatus (Sweet). The Zone corresponds roughly to the Lower Triassic Neogondolella carinata Zone established by Sweet

Fig. 4. SEM photos of conodonts in the uppermost Permian–Lower Triassic strata of the Meishan D section. All specimens are housed in Faculty of Earth Sciences, China University of Geosciences, Wuhan, Hubei Province, P. R. China. All are Pa elements and in an upper view, except 11 and 12 which are ramiform elements with lateral views. 1: Neogondolella changxingensis changxingensis (Wang et Wang, 1981), from Bed 24e of Changxing Fm, ×85, MDP-24e-005. 2: Neogondolella deflecta (Wang et Wang), from Bed 24e of Changxing Fm, ×75, MDP-24e-001. 3 Neogondolella meishanensis zhangi (Mei, 1998), from Bed 24e of Changxing Fm, ×100, MDP-24e-004. 4: Neogondolella meishanensis meishanensis (Zhang, 1995), from Bed 25 of Yinkeng Fm, ×85, MDT-25-001. 5: Neogondolella changxingensis yini (Mei, 1998), from Bed 24a of Changxing Fm, ×85, MDP-24a-003. 6, 13: Neogondolella tulongensis Tian, 1982, 6 is from Bed 54 of Yinkeng Fm, ×170, MDT-54-0001; 13 is from Bed 75 of Helongshan Fm, ×75, MDT-75-002. 7: Neogondolella discreta Orchard et Krystyn, 1998, from Bed 75 of Helongshan Fm, ×85, MDT-75-010. 8, 9: Neogondolella carinata (Clark, 1959), 8 is from Bed 69 of Helongshan Fm, ×125, MDT-69-2-001; 9 is from Bed 56 of Yinkeng Fm, ×150, MDT-56004. 10, 16, 17: Neogondolella planata (Clark, 1959), 10 is from Bed 72 of Helongshan Fm, ×225, MDT-72-2-001; 16 is from Bed 74 of Helongshan Fm, ×125, MDT-74-004; 17 is from Bed 87 of Helongshan Fm, ×335, MDT-87-1-001. 11: Sb element of Ellisonia sp., from Bed 62 of Helongshan Fm, ×85, MDT-62-1-003. 12: Sc element of Ellisonia dinodoides (Tatge, 1956), from Bed 62 of Helongshan Fm, ×100, MDT-62-1-004. 14, 15: Neogondolella taylorae Orchard, 1994, 14 is alpha morphotype and from Bed 53 of Yinkeng Fm, ×110, MDT-53-003; 15 is beta morphotype and from Bed 88 of Helongshan Fm, ×125, MDT-88-1-001.

K. Zhang et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 252 (2007) 4–23

(1970) in West Pakistan, and also corresponds to the N. carinata–N. planata Zone reported by Zhang et al. (1995) at the Meishan D Section. According to this study,

15

I. isarcica disappeared in Bed 51 and Neospathodus kummeli occurred first in Bed 73 at the Meishan D Section; therefore, the base of this zone is defined at the

16

K. Zhang et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 252 (2007) 4–23

base of Bed 52 (Fig. 1) and its top at the base of Bed 73 (Fig. 2). This zone, thus, includes the upper part of the Yinkeng Formation and the lower Lower Member of the Helongshan Formation. Other associated fossils in this zone are the ammonoid Ophiceras sp. and some bivalves such as Pseudoclaraia wangi and Claraia griesbachi. This zone is widely distributed in South China, Tibet, Nepal, Kashmir, India, Pakistan, Italy, Nevada of the USA and Canada (Clark, 1959; Sweet, 1970; Goel, 1977; Tian, 1982; Hatleberg and Clark, 1984; Beyers and Orchard, 1991; Orchard et al., 1994; Belka and Wiedmann, 1996; Zhao et al., 2005). 3.7. Neospathodus kummeli Zone This zone, of a early Dienerian, covers the Beds 73– 92, i.e., from the upper part of the Lower Member to the lower part of the Upper Member of the Helongshan Formation at the Meishan D Section (Fig. 2). Here, Neospathodus kummeli first occurs in Bed 73. It is the index fossil in the fourth conodont zone of the “International Standard Triassic Conodont Zonation” proposed by Sweet (1970). This fossil, however, is not common in China, as it is only known from Nielamu of Tibet (Tian, 1982), Jurong of the Jiangsu Province (Wang, 1993) and Chaohu of Anhui Province (Zhao et al., 2003, 2005). Outside China, this species has been reported in Kashmir, India, Nepal, West Pakistan and Utah (Sweet, 1970; Bhatt et al., 1999; Paull, 1982). 3.8. Neospathodus cristagalli–N. dieneri Zone This late Dienerian zone begins with the FAD of Neospathodus cristagalli (Huckriede) and ends with the FAD of Neospathodus waageni Sweet in the Lower Yangtze region (Wang, 1993). At the Meishan D Section, N. cristagalli first occurs in Bed 93 and ranges up to Bed 111, thus this zone covers the upper part of the Upper Member of the Helongshan Formation and the base of the Nanlinghu Formation (Beds 93–111, Fig. 2), the upper limit is undefined by present data, because of the N. waa-

geni having not been found and the erosion of the upper part of the Nanlinghu Fm (Zhang et al., 2005). This zone also occurs in Laohushan, Yixin, Jiangsu; Dalishan, Jurong, Jiangsu; Majiashan, Chaoxian, Anhui; Ziyun, Guizhou; and Zuodeng, Tiandong, Guangxi in China (Ding, 1983; Yang et al., 1986; Wang, 1993; Zhang and Yang, 1993), as well as in Kashmir, Nepal, Pakistan, Oman, Utah and Canada (Sweet, 1970; Paull, 1982; Beyers and Orchard, 1991; Orchard, 1995; Bhatt et al., 1999). 4. Palynological assemblage Eighty-two palynomorph samples have been collected from 15 m of strata in the Yinkeng Formation (Bed 25–Bed 62) at the Meishan D Section, 12 of which yielded palynomorph fossils. Detailed taxonomic study of the palynomorphs reveals 50 species belonging to 47 genera (including 4 genera of acritarchs, 2 kinds of trachieds and the algal) (Table 3). A palynological assemblage from the Yinkeng Formation, the Lundbladispora–Taeniaesporites–Equisetosporites assemblage, is herein proposed (Fig. 1). This assemblage is dominated by gymnosperm pollen (59.0–79.6%) and fern spores (20.4–40.9%) (Table 3). Among the gymnosperm pollen, the instriate biasaccate pollen types are the main forms (19.7–54.4%) in which the coniferousbisaccate pollen is the most common, and the striate bisaccate pollen types followed the former in abundance. The polyclicate pollen is represented only by one genus Equisetosporites but this genus has a rather high abundance (up to 24.3%). Among the fern spores, Leiotriletes is quite common (14.3–24.4%). Echinate, granular and verrucose trilete spores also present but less frequent in the samples analyzed (1.9–21.2%). Fastigiate trilete spores, mainly Lundbladispora, is relatively low in proportion but was found in most studied horizons. Zonotrilete spores are rare in abundance and diversity. In this palynological assemblage, Lundbladispora is an index form of the Early Triassic (Ouyang, 1982; Ouyang and Utting, 1990). This assemblage also contains the Permian-type forms, such as Vittatina and Lueckisporites virkkiae (Balme, 1970) and a few Middle

Fig. 5. Palynomorph fossils found in the Yinkeng Fm. of the Lower Triassic in the Meishan D Section. All specimens are housed in the Faculty of Geosciences, China University of Geosciences, Wuhan, Hubei, P. R. China. All illustrations are magnified by 800 times. 1: Lundbladispora sp., from Bed 51, S 51-3/2-29. 2: Leiotriletes concavus, from Bed 45, S 45-1/3-6. 3: Leiotriletes sp., from Bed 33, S 33-1/2-13. 4: Leiotriletes directus, from Bed 47, S 47-2/1-19. 5: Lunizisporites sp., from Bed 37, S 37-3/2-17. 6: Cyclogranisporites sp., from Bed 33, S 33-1/2-9. 7: Leiotriletes exiguous, from Bed 45, S 45-1/3-5. 8: Apiculatisporites bulliensis, from Bed 44, S 44-1/2-1. 9: Cycadopites complanatus, from Bed 38, S 38-1/3-26. 10: Osmundacidites fissus, from Bed 47, S 47-2/1-25. 11: Punctatisporites minutus, from Bed 51, S 51-3/2-24. 12: Vittatina sp., from Bed 47, S 47-2/1-24. 13, 14: Equisetosporites chacheutensis, 13 is from Bed 51, S 51-3/2-30; 14 is from Bed 47, S47-2/2-31. 15: Alisporites sp., from Bed 47, S 47-2/1-20. 16: Lueckisporites virkkiae, from Bed 38, S 38-1/3-24. 17: Alisporites toralis, from Bed 33, S 33-1/1-28. 18: Taeniaesporites pellucidus, from Bed 38, S 38-1/3-10. 19: Pinuspollenites sp., from Bed 44, S 44-1/2-5. 20: Piceites notialis, from Bed 33, S 33-1/2-10. 21: Taeniaesporites kraeusselis, from Bed 44, S 44-1/1-13. 22: Lueckisporites triassicus, from Bed 38, S 38-1/1-30. 23: Platysaccus alatus, from Bed 38, S 38-1/3-18. 24: Cycadopites sp., from Bed 51, S 51-3/228. 25, 26: Cycadopites nitidus, 25 is from Bed 47, S 47-2/3-37; 26 is from Bed 53, S53-5/2-31.

K. Zhang et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 252 (2007) 4–23

and Late Triassic forms, such as Aratrisporites, Dictyophyllidites and Lunzisporites, which flourished in the Middle and Late Triassic (Qu and Wang, 1986).

17

This palynological assemblage from the Meishan D Section can be precisely correlated with the Aratrisporites–Lundbladispora assemblage from the early

18

K. Zhang et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 252 (2007) 4–23

Scythian Kayitou Formation of East Yunnan, China (Ouyang, 1982; Peng et al., 2005) (Table 4): (1) most of the “Paleozoic” miospores persisted into the Early Triassic in these two sections. (2) Spores of Pterdophyta and Pteridospermae are common, but gymnospermous pollen is dominant in the proportion of individuals. (3) The index fossil for the Early Triassic, Lundbladispora, has been discovered in these two sections. The palynological assemblage from the Meishan D Section is different from its counterpart from the Jiucaiyuan Formation — a suite of terrestrial red beds in the Junggar basin, northern Xinjiang, northwest China (Table 4), and the Jiucaiyuan Formation contains a Lystrosaurus fauna (Qu and Wang, 1986). Samples from the latter are often dominated by pteridophyte spores, mainly including Limatulasporites, Lundbladisporites, Neoraistrickia, Cyclogranisporites and Aratrisporites, and by Gymnosperm pollen, especially non-taeniate disaccate forms (e.g. Alisporites) (Ouyang and Utting, 1990). This miospores assemblage from the red beds in Junggar basin are more diverse in composition and are better preserved than that from the Yinkeng Formation, Meishan D Section. If the varied facies and phytoprovincialism (northern Xinjiang belongs to the Angara Province and Zhejiang belongs to Cathaysian Province, according to macrofossil plant data Ouyang, 1986) are taken into account, the similarity is still striking: Gymnosperm pollen dominates in the Yinkeng Formation and Jiucaiyuan Formation (see above). The present assemblage may be correlated with the Taeniaesporites Association of Kap Stosch, East Greenland (Balme, 1980) except that the latter has a higher proportion of spinose acritarchs and the former rarely contains spinose acritarchs. In addition, present assemblage is different from the counterpart of the Kathwai and Mittiwali Members of Early Triassic in the Salt Range, West Pakistan (Balme, 1970) by the latter is lower in diversity, and has abundant presences of small spinose acritarchs and indistinctive Leiospheres. This difference suggests the land vegetation in the Meishan area was more diverse than that in Kap Stosch and Salt Range, or suggests the composition of palynomorph assemblage varied over the differences of the phytoprovincialism and sedimentary facies. 5. Discussion 5.1. Advances in the study of conodont zones As mentioned by the part of introduction, the conodont biostratigraphy of the interval from the Upper Permian Changhsingian to the Lower Triassic at the Meishan D

section has been extensively studied. For example, four conodont zones from the Permian–Triassic boundary beds were proposed in ascending order: Clarkina (= Neogondolella) changxingensis–C. deflecta (beds 24a–27b) Zone, Isarcicella parva (=Hindeodus parvus) Zone (beds 27c–27d), I. isarcica Zone (beds 28–29b) and C. carinata–C. planata Zone (bed30), and the C. changxingensis–C. deflecta Zone was further subdivided into three faunas in ascending order: changxingensis–deflecta–subcarinata Fauna (beds 24a–24e), lantidentatus–meishanensis Fauna (beds 25–26) and typicalis Fauna (beds 27a–27b) (Zhang et al., 1995, 1996). However, among these zones, the upper limit of the N. carinata–N. planata Zone was not been defined because N. kummeli was not found (Zhang et al., 1995). In 1998, three conodont zones from the Permian–Triassic boundary beds were recognized in ascending order: C. changxingensis yini–C. meishanensis zhangi Zone (beds 24a–24e), C. meishanensis meishanensis Zone( beds 25–26) and C. zhejiangensis Zone (beds 27a–27d), based on the study of the neogondolellid sequence (Mei et al., 1998). Compared to the above lists, several advances have been made herein: (1) the conodont zone from the boundary clay beds is reconsidered, e. g. the Neogondolella meishanensis meishanensis–Hindeodus eurypyge Zone, has been defined based on considering the abundances of Neogondolella and Hindeodus genera in the boundary clay beds (Figs. 1 and 2; Tables 1 and 2); (2) I. staeschei Zone has been recognized below the I. isarcica Zone for the first time at the Meishan D Section based on the occurrence of I. staeschei is lower than that of I. isarcica at the Meishan D Section; (3) The upper limit of N. tulongensis–N. planata Zone is defined. The top limit is marked by the occurrence of Neospathodus kummeli Sweet. 5.2. Correlation between conodont zones and palynological assemblage The conodont Isarcicella isarcica Zone to the lower part of Neogondolella tulongensis–N. planata Zone are roughly correlated with the palynological assemblage Lundbladispora–Taeniaesporites–Equisetosporites in the Meishan D Section. The conodont I. isarcica and Neogondolella tulongensis–N. plana zones distributed at many sections around the world (see the part of conodont stratigraphy), and are of well spatial comparative. This palynological assemblage is correlated with the counterparts in Yunnan, China and East Greenland, although it is different from the counterparts from the terrestrial facies in Junggar basin and West Pakistan because of the difference in sedimentary facies or phytoprovincialism (see the part

K. Zhang et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 252 (2007) 4–23

19

Table 3 Bed no.

33

38

40

43

44

45

47

51

52

53

Sample no.

33-1

38-1

40-1

43-1

44-1

45-1

47-2

51-3

52-3

53-1

Leiotriletes sp. L. adrienniforumis L. concavus L. directus L. exiguous Dictyophyllidites sp. D. mortoni Calamospora sp. Punctatisporites sp. P. microtumulosus P. triassicus P. minutus Cyclogranisporites sp. C. crassirimosus C. major C. pseudoxonotriletes C. aureus Apiculatisporites sp. A. perirugosus A. decorus A. belliensis Osmundacidites sp. O. fissus Lunzisporites sp. L. pallidus Convolutisporites sp. Neoraistrickia irregularis Acanthriletes sp. Gulisporites cochlearius Lophozontriletes sp. Annulisporites sp. A. folliculosa Lundbladispora sp. L. nejburgii L. watangensis Limatulasporites sp. Muerrigerisporis sp. Endososporites sp. Retusotriletes sp. Aratrisporites sp. A. yunnanensis Netusotriletes rigidus Cycadopites sp. C. complanatus C. nitidus Chasmatosporites sp. C. hians Equestosporites sp. E. chacheutensis Alisporites sp. A. australis A. toralis A. thomasii A. parvus Caytonipollenites sp. Pinuspollenites sp.

4.8

1.9 0.9

0.1

4.8

4.0

6.4

4.6

6.1

3.0

1.6

53-5

53-10

3.6

2.7

1.3

1.4 0.9

3.2

0.9 0.9

1.0

1.3

1.5 0.9

1.6 8.1

6.5 0.9 1.9

1.6 3.2

6.4

3.2 1.6

7.0 1.0 3.0 3.0

1.3 6.4 1.3 1.3 1.3 3.8

6.5 0.9 1.9 2.8

1.5 1.5 4.5 3.0 1.5 3.0 3.0 1.5

1.4 6.1

0.1

8.9

6.8

1.8

1.4 4.1

1.5 4.5 3.6 1.5 1.5

3.2

1.6

1.6

1.0

1.0 1.0

0.9

1.3 2.6

1.3

4.5 1.5

1.9 0.9 0.9

1.5 0.1 0.1

0.9 1.6

0.9

2.0 1.0

1.3

1.5 0.9

3.0

1.5 1.5 3.0

2.7 1.8 1.8 1.8

1.4

1.8 1.8

1.4

2.8 0.9 1.6

1.6

1.3

0.9 3.2 1.6

0.9

3.2 1.6

1.0 2.0

2.6 1.3

1.9

3.0

1.8

1.5

1.6

2.7 1.4

1.5 1.3 1.0 1.0

1.6

0.9 0.9

4.8

0.9 0.9

1.6

0.9

8.1 1.6 4.8

0.9

1.6

9.7

0.9 1.9 1.9

11.1

2.6 1.3

1.5 1.5

1.6

1.5

1.6

2.6

2.8

1.5

5.0 3.0 5.0

1.6 3.2

4.0

1.6

2.0 4.0 2.0

6.4 3.8 3.8 1.3

1.3 1.3 2.6

4.6 1.9 7.4 0.9 3.7

0.9 6.5

3.0 1.5

0.5 15.2 9.1 3.0

3.0

4.5

1.4 1.4

1.8

1.4

7.1 3.6 1.8

8.1 4.1 2.7

1.8

1.4

3.6 16.1

1.4 16.2

3.0

0.9 2.8 3.2 3.2 6.4

3.6

1.5 1.5

0.2

(continued on next page )

20

K. Zhang et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 252 (2007) 4–23

Table 3 (continued ) Bed no.

33

38

40

43

44

45

47

51

52

53

Sample no.

33-1

38-1

40-1

43-1

44-1

45-1

47-2

51-3

52-3

53-1

2.8 3.7

0.1 4.8

3.0

3.8

1.9 3.7

3.0 6.1

3.2

6.0

6.4

0.9 1.9

3.0 1.5 1.5

1.3

1.9

P. divulgatus Piceites sp. P. notialis Podocarpidites sp. Pityosporitres sp. P. devolvens Platysaccus sp. P. alatus Caytonipollenites pallidus C. subtilis Klausipollenites schauberger Chordasporites pallidus Chordasporites sp. Taeniaesporites pellucidus T. labdcus T. kraeuselis T. sp. Luckisporites vikkiae L. sp. Striatopodocarpidites sp. Psophosphaera sp. Gardenasporites minor Vittatina sp. Baltisporites sp. Polygonium sp. Total content of fern spores Total content of gymnosperm pollen

1.6 3.2 1.6 1.6

1.6

6.5 4.6 1.9 4.6 1.9 0.9

1.6

0.1 0.2

53-5

53-10

3.6

6.8 1.4

1.8

1.5

1.4

0.9 0.9 1.6

1.6

3.7

1.6

0.9 2.8

2.0

3.2

10.2 1.9

0.1

1.6 1.6

4.8 3.2 1.6

1.0 5.0 1.0 1.0 2.0

2.8

2.8

2.6 3.8 1.3

1.4

4.6

4.5

0.9 1.9

1.5

4.5

0.1

5.4

1.4 4.1

3.0

1.0

1.5

1.8 3.6

4.1

1.8

4.1

32.2 67.8

0.1 32.4 67.6

0.1 1.0

1.3

2.8

1.5

0.1 37.1 62.9

0.1 20.4 79.6

0.2 30.6 69.4

of Palynological Assemblage). So it seems that these conodont zones are correlative in global and this palynological assemblage are correlative and valuable for the stratigraphical subdivision. It is more significant that, present palynological assemblage is correlated with the counterpart from the terrestrial facies, such as Yunnan. This discovery makes it possible that the strata in non-marine facies could be correlative with the strata in marine facies by palynological assemblage and conodont zones. The occurrences of Lundbladispora or Taeniaesporites, or the abundant presence of Equisetosporites is equal to the condont Isarcicella isarcica Zone to the lower part of Neogondolella tulongensis–N. planata Zone. 5.3. Turnovers of palynomorph and conodont fossils and mass extinction The records from marine and non-marine palynomorph fossils indicate that the plants experienced a two-phased mass extinction across the Permian–Triassic boundary: a major decline at the PTB (first phase) and a minor extinction of the relicts in earliest Triassic (second phase) (Fang, 2004; Xie et al., 2005). In addition, the Permian

30.0 70.0

40.1 59.0

29.6 70.4

33.3 66.7

40.9 59.1

palynomorph survived into Triassic and were mixed with the Triassic elements in present assemblage (see above). These phenomena also occurred in the southwest of China (Yu et al., 2007) and East Greenland (Balme, 1980), indicating the plants were also affected by a stressed environment in the Permian–Triassic transition. What's more, the decline pattern (two-phased extinction) of palynomorph fossils is corresponding with that of marine invertebrates in South China (Yin, 1996; Fang, 2004). On the contrary, the conodont did not decline in species diversity, indicating conodont did not become extinct at the end Permian; therefore, the change of conodont is different from that of the palynomorph fossil and also different from that of most invertebrates in the mass extinction event. Why the conodont survived at the end Permian is explained below. An anoxia event occurred in the latest Permian to the earliest Triassic in many sections around the world, and it is considered as one of the causes which led to the mass extinction (Wignall and Twitchett, 1996; Isozaki, 1997). During this anoxic age, the conodont Hindeodus behaved with Neogondolella in a different way. The genus of Hindeodus appears to be a planktonic form because its fossils can be found at various water depths

K. Zhang et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 252 (2007) 4–23

(Lai et al., 2001), while the genus of Neogondolella appears to be a free benthic and nektonic conodont form, because it can be frequently found in offshore or relatively deep oxidized environments, and because it declined in the abundance and in the number of occurring locations during the Permian−Triassic anoxia event but still occurred in some oxidized areas, such as Neogondolella changxingensis changxingensis, N. deflecta (Lai et al., 2001). When the anoxia event presented, the planktonic conodont Hindeodus could adapt to it, survived, and even became more abundant in species diversity, such as in Meishan the Hindeodus became abundant in species, while the benthic conodont Neogondolella dropped in species diversity. The replacement from the abundances of Neogondolella to the abundances of Hindeodus is coincident with the seabottom anoxia at the Meishan Section (Wignall and Hallam, 1993; Lai et al., 2001). So only replacement of taxa but no extinction happened to conodonts in the Permian–Triassic intervals. Previous literatures also suggested that the conodont Neogondolella was replaced by Hindeodus during the late time of the Permian–Triassic transition in many areas such as South

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China, Salt Range, Iran, Europe and western America (Zhang et al., 1995; Orchard, 1996; Lai et al., 2001; Nicoll et al., 2002). 6. Conclusions Based on our detailed research on the conodont biostratigraphy from the interval of the Permian–Triassic boundary and the Lower Triassic in the Meishan D Section of Changxing, Zhejiang Province, South China, 8 conodont zones, Neogondolella changxingensis yini–Hineodus praeparvus Zone, Neogondolella meishanensis meishanensis– Hindeodus eurypyge Zone, Hindeodus parvus Zone, Isarcicella staeschei Zone, Isarcicella isarcica Zone, Neogondolella tulongensis–N. planata Zone, Neospathodus kummeli Zone and Neospathodus cristagalli–N. dieneri Zone have been recognized. A rough correlation between palynological and conodont biostratigraphy in the Meishan D Section is also established. The palynological assemblage Lundbladispora–Taeniaesporites–Equisetosporites is correlated with the conodont I. isarcica Zone and the lower part of the Neogondolella tulongensis–N planata Zone of the Yinkeng Formation.

Table 4 Correlation of the palynological assemblages from the Early Triassic in China Age

South China (this paper)

Southwest China (Ouyang, 1982; Peng et al., 2005)

Northwest china (Ouyang and Utting, 1990)

Spores of PP⁎ and PS⁎ total 40%. Pollen of GS⁎ 60%. Important elements: Aratrisporites, Lundbladispora, Cycloverru-triletes, Cordaitina, Voltziaceaesporites, Lueckisporites, and other Disaccate Striatiti. Cycadopites and Ephedripites Abundant Aratrisporites and occasional Early In the middle and upper parts of lower Spores of PP⁎ and PS⁎ dominant in the or rare Lundbladispora. Pollen of GS⁎ Yinkeng Formation: Spores of PP⁎ and lower part. Pollen of GS⁎ became dominant at approximately 30m above the dominant, including: Luckisporites, PS⁎ total 18%. Pollen of GS⁎ 77%. base, where they total 60–80%. Disaccate Taeniaesporites, Protohaploxypinus, Important elements: Leiotriletes, Cyclogranisporites, Apicu-latasporites, Striatiti not very abundant. Main elements: Striato-abietites, Cordaitina, Pteruchipollenites reticorpus, Protopinus Vitreisporites, Klausi-pollenites, Klausipollenites, Aratri-sporites, Piceaepollenites, Abiespollenites, and fuyuanensis, Striatopodocarpites, and Lundbladispora, Cycloverru-triletes, some Paleozoic elements such as Lueckisporites? Cordaitina, Voltziaceaesporites, Scutasporites, Fuldaesporites, and Lueckisporites, Lunatisporites, and Illinites Ephedripites Sudden change In the basal part of the lower Yinkeng 30m above base of Triassic Aratrisporites Formation: Spores of PP⁎ and PS⁎ total yunnanensis, Lundbladispora spp., Eupunctisporites chinensis, 33%. Pollen of GS⁎ 67%. Important Dictyophyllidites mortoni, and elements: Puntatisporites, Cyclogranisporites, Ara- trisporites, Apiculatasporites perirugosus Lundbladispora, Luckisporites, Taeniaesporites, Alisporites, and other disaccate pollen. Cycadopites and Equesetosporites.

Early Late Triassic

Unknown

Unknown

⁎PP = pteridophyta; ⁎PS = Pteridospermae; GS = Gymnospermae.

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