Quantitative stratigraphic correlation of the Lower Triassic in South China based on conodont unitary associations

Journal Pre-proof Quantitative stratigraphic correlation of the Lower Triassic in South China based on conodont unitary associations Kui Wu, Jinnan Tong, Ian Metcalfe, Lei Liang, Yifan Xiao, Li Tian

PII:

S0012-8252(19)30477-5

DOI:

https://doi.org/10.1016/j.earscirev.2019.102997

Reference:

EARTH 102997

To appear in: Received Date:

16 July 2019

Revised Date:

29 October 2019

Accepted Date:

29 October 2019

Please cite this article as: Wu K, Tong J, Metcalfe I, Liang L, Xiao Y, Tian L, Quantitative stratigraphic correlation of the Lower Triassic in South China based on conodont unitary associations, Earth-Science Reviews (2019), doi: https://doi.org/10.1016/j.earscirev.2019.102997

This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier.

Quantitative stratigraphic correlation of the Lower Triassic in South China based on conodont unitary associations

Kui Wu1,2, Jinnan Tong1*, Ian Metcalfe2*, Lei Liang3, Yifan Xiao1, Li Tian1

1

State Key Laboratory of Biogeology and Environmental Geology, School of Earth

2

ro of

Sciences, China University of Geosciences (Wuhan), Wuhan 430074, China

Earth Sciences, Earth Studies Building C02, School of Environmental and Rural

Science, University of New England, Armidale, NSW 2351, Australia

-p

Hebei GEO University, 136 Huaiandonglu, Shijiazhuang 050031, China

re

3

* Corresponding authors: [email protected] (Jinnan Tong); [email protected] (I.

na

ur

Abstract

lP

Metcalfe)

Unitary Association Method (UAM) analyses of conodont faunas from 28 sections

Jo

spanning the biggest Phanerozoic end-Permian mass extinction and significant global environmental and ecosystem perturbations during the succeeding Early Triassic are presented. Based on 72 conodont species, 26 Unitary Association Zones (UAZs) are established for the latest Permian to earliest Middle Triassic of South China. These UAZs provide quantitative high-resolution tools to correlate sequences in the Early

Triassic of South China and to compare and test high-resolution conodont biostratigraphy based on interval conodont zones developed over the past three decades. Our quantitative analyses provide insights on ongoing debates relating to the First Appearance Datum (FAD) of the conodont Hindeodus parvus which is used to place and subsequently correlate the “Golden Spike” defining the base of the Triassic (Permian-Triassic Boundary) at the base of Bed 27c at the GSSP Meishan D Section.

ro of

Previous proposals that suggested potential earlier occurrences of H. parvus below its FAD at Meishan section are not supported by our results. In deep water sections, the

First Occurrence (FO) of H. parvus lies at the base of UAZ 5 at the Bianyang section

-p

while it lies within UAZ 6 at the Meishan section. This indicates that the earliest

re

occurrence of H. parvus in South China is in the Bianyang section but this conclusion needs further testing due to the reliance on “spot” data by the UAM. Anomalously

lP

high occurrences of Hindeodus in the Mingtang section (close to the Bianyang section)

na

further suggests that the Bianyang-Mingtang area may have provided a temporally extended habitable zone for anchignathodontid conodonts. Stage boundaries currently

ur

proposed or established using interval conodont zones locate within or between UAZs and are difficult to correlate with carbon isotope curves. UAZs are useful in helping to

Jo

define GSSPs by recognizing which correlations are most robust and in the selection of the most appropriate species and level for GSSPs.

Key words: South China, Quantitative stratigraphy, Unitary association, Early Triassic,

Conodonts

1. Introduction Past extinction events provide analogs to help us predict the impact of current and projected future environmental changes that have significant impact on the Earth’s biota (Harnik et al., 2012; Payne et al., 2016). The Paleozoic-Mesozoic

ro of

transition witnessed the most severe ecosystem change in Earth history and a major change from Paleozoic to modern marine ecosystems (Bambach et al., 2002). This

ecosystem turnover is marked by the largest Phanerozoic mass extinction at the end of

-p

the Permian, and delayed biotic recovery throughout the Early Triassic (e.g. Erwin,

re

1994; Payne et al., 2004; Chen and Benton, 2012; Wei et al., 2015). Numerous studies have revealed that the mass extinction process involved complex biotic and

lP

environmental devastations, and was followed by continued environmental

na

perturbations (e.g. Payne et al., 2004; Bond et al., 2010; Joachimski et al., 2012; Yin et al., 2012; Sun et al., 2012; Song et al., 2014; Shen and Bowring, 2014; Chen et al.,

ur

2015; Shen et al., 2018). In the aftermath of the mass extinction hypoxia-anoxia and climatic warming/cooling occurred episodically throughout the Early Triassic (Sun et

Jo

al., 2012; Tian et al., 2014; Grasby et al., 2013, 2016) and marine organisms exhibited dynamic and recurrent changes before the re-organization of the ecosystem (e.g. Stanley, 2009; Chen and Benton, 2012; Song et al., 2011, 2014, 2018; Dai et al., 2018; Wu et al., in press). To understand these processes in detail, the establishment of a correlative and

high-resolution bio-zonation is important. As the feeding apparatus of free swimming marine animals, conodonts are widely distributed in various marine basins, from Cambrian to Triassic (Aldridge et al., 1986; Goudemand et et., 2011). During the late Paleozoic and early Mesozoic, conodont elements evolved rapidly and they have been utilised to formally recognise the Global Stratotype Section and Points (GSSPs) for most stage boundaries of the Permian and Triassic using the First Appearance Datum

ro of

(FAD) of index conodont species. For example, the FAD of Hindeodus parvus at the base of bed 27c at Meishan D section was used to position and correlate the now

ratified GSSP for the base of the Triassic and Permian-Triassic boundary (PTB) (Yin

-p

et al., 2001, 2012). High-precision CA-TIMS U-Pb zircon dating provides isotopic

re

ages for Beds 25 and 28 of the Meishan D section of 251.941 ± 0.037 Ma and 251.880 ± 0.031 Ma, respectively, which constrains the duration of the extinction to as little as

lP

60 ka (Burgess et al., 2014). Five conodont interval zones can be established from the

na

Permian-Triassic transition beds at the GSSP (Jiang et al., 2007; Yin et al., 2012; Chen et al., 2015) and indicate that conodont biozones provide higher resolution correlation

ur

than isotope geochronology during P-Tr transition. Furthermore, utilizing conodont biozone correlation, two principal episodes of extinction have been recognized within

Jo

the stepwise extinction interval, which was calibrated and correlated by isotope geochronology (Shen et al., 2011; Song et al., 2013). Similarly, the extinction near the Smithian-Spathian boundary (SSB) in the Early Triassic has also attracted much attention (Brayard et al., 2009; Stanley et al., 2009), and recent studies indicate that dramatic environmental changes happened during this interval (Sun et al., 2012; Chen

et al., 2013; Goudemand et al., 2019). However, debates about temperature changes across the SSB remain with conflicting reports of warming or cooling at the SSB (Sun et al., 2012; Goudemand et al., 2019). The apparent contradictions of warming or cooling at the SSB are in fact due to differing definitions of the SSB by different authors. Sea surface temperatures indicating warming or cooling are derived from conodont oxygen isotopes and high-resolution conodont biostratigraphy indicates that

ro of

the apparent discrepancies of warming and cooling events at the SSB are due to different proposals for recognition of the "SSB" (yet to be formally defined and

ratified) by different research groups (Sun et al., 2012; Goudemand et al., 2019; Wu et

-p

al., in press).

re

Ideally, the FAD of a species within an evolutionary cline used to recognise ("define") and correlate a GSSP should be the earliest occurrence of that species

lP

anywhere in the world and thus represent its true evolutionary appearance (Henderson

na

2006). It is however often very difficult to demonstrate or prove this. A first occurrence (FO) of this species at any other section is theoretically either correlative

ur

or younger than that at the GSSP (Henderson, 2006). Thus, the PTB in the Meishan Section D GSSP section is interpreted to represent the true evolutionary appearance of

Jo

Hindeodus parvus (Henderson, 2006) and the FO of this species in other sections, for example Shangsi in China (Jiang et al., 2007) and Opal Creek in Western Canada (Henderson, 1997), could not be used to define the PTB. Assuming that the carbonate stable carbon isotope negative excursion in the shallow water Dajiagou section is synchronous with that in the deeper water Meishan section, the FO of H. parvus in

Dajiagou appears to be earlier than the FAD of H. parvus in Meishan (Yuan et al., 2015). In addition, the FO of H. parvus in the Zhongzhai section has also been interpreted to be earlier than the FAD at Meishan (Zhang et al., 2014). Both the Zhongzhai and Daijiagou sections are shallow water sections and may have some strata missing due to the regression at the end of the Permian (Yin et al., 2014). What’s more, solution of limestone units now missing and reworking of conodont

ro of

elements (Jiang et al., 2014) could produce an apparent earlier occurrence of H. parvus than the FAD in Meishan.

Contradictions between the FO and FAD of species are the result of

-p

biogeographic dispersal rates, local conditions, sample bias and selective preservation,

re

which can lead to misleading fossil records (Fig. 1, Guex, 1991). For example, taxa in different sections may have different temporal ranges and different order and

lP

conflicting FOs between the sections (Brosse et al., 2016). Relying on the FO or FAD

na

of specific taxa, to establish a traditional interval zone within a single section ignores much information that can be synthesized from multiple sections or an entire region

ur

(Chen et al., 2019). In contrast, relying on the whole fossil record, Unitary Association Zones (UAZs) are defined by both the appearances and disappearances of

Jo

characteristic species and the Unitary Association Method (UAM) is able to resolve conflicting FOs in multiple sections (Brosse et al., 2016). The UAM can provide valuable information to assist correlations particularly where discontinuous records or poor sample coverage exists, although the fact that UAZ is not applicable without index fossils and this method is unable to be refined resolution unless all the data with

additional data are re-performed under Unitary Association software (Xiao et al., 2018a). In this study, we compile the published Early Triassic conodont data from 28 sections of South China, and establish a UAM based conodont UA biozonatiation for the Early Triassic of South China using these conodont records i. e. much larger database than that previously used by Brosse et al. (2016). The UAZ provide a higher

ro of

resolution correlation for the Early Triassic than the traditional interval zones.

However, some limitations still remain, including the weak correlation between the

UAZ and carbon isotope records. In addition, the discrete and discontinuous nature of

ur

na

lP

re

-p

UAZs in a continuous section and temporal discordance of UAZs are problematic.

Jo

Fig. 1. The spatial and temporal distribution of a taxa x (Modified after Guex, 1991). X and y axis represent the spatial and temporal distribution of taxa. J(x) represents the total temporal range of taxa x, while the lowest point represents its FAD. Dotted line represents the FO and LO of this taxa in one section.

2. Geological setting

During the Paleozoic-Mesozoic transition, South China was located within the eastern Tethys and close to the equator (Metcalfe, 2017). There are three main depositional regions (with distinctive facies) in South China during the Early Triassic, namely the Northern Marginal Basin of the Yangtze platform, the Yangtze Carbonate Platform and the Nanpanjiang Basin (Feng et al., 1997). Many studies of Lower Triassic stratigraphy and biostratigraphy have been carried out in South China and

ro of

many well-studied sections with conodont sequence information have been published. In this study, 28 sections from South China are chosen for unitary association analysis

Jo

ur

na

lP

re

-p

(Fig. 2, Table 1).

Fig. 2. Early Triassic paleogeographic map of South China. Modified from Feng et al., 1997. Abbreviations: NMBY = Northern marginal basin of Yangtze Platform; SS = Shangsi; CT = Chaotian; DXK = Daxiakou; JS = Jianshi; GX= Ganxi; PDS = Pingdingshan; MS = Meishan, HZS= Huangzhishan; YG = Yangou; GH = Gaohua; JZS = Jianzishan; DJG = Daijiagou; LFY = Liangfengya; QY = Qingyan; MT =

Mingtang; GM = Gaimao; JR = Jiarong; ZZ = Zhongzhai; BY = Bianyang; GD = Guandao; SDZ = Sidazhai; GHQ = Ganheqiao; DW = Dawen; DJ = Dajiang; PJ = Pojue; DL = Dala; MTL = Motianling; WZ = Wuzhuan; TP = Taiping.

2.1. Northern Marginal Basin of the Yangtze Platform The Northern Marginal Basin was situated on the northern flank of the Yangtze

ro of

Carbonate Platform. During the collision between South China and North China, the water depth in this basin became progressively shallower during the Early Triassic.

Seven sections are chosen from this area, which are the Shangsi, Chaotian, Daxiakou,

-p

Jianshi, Ganxi, Pingdingshan and Meishan sections. In the upper Yangtze area, the

re

Shangsi and Chaotian sections span the uppermost Permian Dalong Formation and Lower Triassic Feixianguan Formation. In the middle Yangtze area, the Daxiakou,

lP

Jianshi and Ganxi sections span the uppermost Permian Dalong Formation and Lower

na

Triassic Daye and Jialingjiang Formations. In the lower Yangtze area, the uppermost Permian Dalong Formation and Lower Triassic Yinkeng, Helongshan and Nanlinghu

ur

Formations are developed at the Meishan and Pingdingshan sections.

Jo

2.1.1. Shangsi section, Guangyuan, Sichuan Province (Jiang et al., 2011) Located in the Changjianggou valley, Shangsi town, Guangyuan city, Sichuan

province, South China (Fig. 2), this section was formerly one of the candidate sections for the GSSP of the PTB. Analysis of sedimentary features indicates that this section belongs to deeper-water facies compared to the GSSP Meishan section during the

Permian-Triassic transition (Yin et al., 2001). In the Shangsi section, Upper Permian strata include the Wuchiaping and Dalong Formations. The Wuchiaping Formation consists of siliceous limestone and the Dalong Formation comprises siliceous limestone and interbedded shale. The lowermost Triassic of this section is the Feixianguan Formation, which comprises mudstone, marl and volcanic ash. Jiang et al. (2011) reported the most detailed study of condonts from the uppermost Dalong

ro of

Formation and the lowermost Feixianguan Formation and established parallel

gondolellid and hindeodid zonations. It is noteworthy that the PTB in this section is not at the same level as the FO of H. parvus, but at a lower level within the H.

-p

changxingensis zone (Jiang et al., 2011; Yin et al., 2014). Recently, an integrated

re

study at Shangsi including conodont biostratigraphy and U-Pb geochronology also

lP

support this conclusion (Yuan et al., 2019).

na

2.1.2. Chaotian section, Guangyuan, Sichuan Province (Ji et al., 2007) This section is located in northern Sichuan, ca. 30 km to the north of Guangyuan

ur

City and about 60 km to the east of the Shangsi Section (Fig. 2). The Chaotian section spans the Middle to late Permian and the overlying Lower Triassic. Detailed conodont

Jo

work has been reported from the uppermost Dalong Formation (Changhsingian) and the lowermost Feixianguan Formation (Ji et al., 2007). Conodont elements are more abundant in the Dalong Formation than in the Feixianguan Formation, and there is a zone with no conodonts (a "gap") before the FO of H. parvus (Ji et al., 2007).

2.1.3. Daxiakou section, Xingshan, Hubei Province (Zhao et al., 2013) This section is located 6 km east of Xiakou Town, in Xingshan County, western Hubei Province, South China (Fig. 2). The Permian and Triassic successions are complete and well exposed in this section. The Wuchiaping and Dalong Formatons constitute the uppermost Permian and the Daye and Jialingjiang Formations constitute the Lower Triassic. Here, the Dalong Formation is composed of medium-bedded

ro of

muddy limestone and the Daye Formation is characterized by alternations of

calcareous mudstone and thin-bedded muddy limestone and thin-bedded to thick

dolomitic limestone and dolomite, which represent shelf basin and carbonate ramp to

-p

peritidal settings respectively (Tong et al., 2007). Wang and Xia (2004) first reported

re

PTB conodonts from this section, and Zhao et al (2013) reported more detailed

lP

conodont research from the latest Permian to the earliest Spathian.

na

2.1.4. Jianshi and Ganxi sections, Enshi, Hubei Province (Lyu et al., 2017) The Jianshi and Ganxi sections both consist of uppermost Permian and Lower

ur

Triassic strata. These two sections are located 20 km and 30 km to the north of Enshi city, Hubei Province, respectively (Fig. 2). The uppermost Permian is represented by

Jo

the Dalong Formation, which comprises black siliceous limestone and mudstone intercalated with gray limestone. The Lower Triassic consists of the Daye and Jialingjiang formations, the former of which is dominated by an alternation of gray calcareous mudstone and thin bedded muddy limestone, while the latter is dominated by massive muddy limestone. During the Permian-Triassic transition, both sections

belong to a carbonate ramp setting. Lyu et al. (2017) made a detailed conodont study of these two sections, their results indicated that the Jianshi section has better PTB and IOB conodont records while the record from the Ganxi section is poorer but still useful.

2.1.5 Pingdingshan section, Chaohu City, Anhui Province (Zhao et al., 2008; Liang et

ro of

al., 2011)

In Chaohu city, the Majiashan-Pingdingshan syncline is located in the

northwestern suburb. Three main sections, namely the South Majiashan, West

-p

Pingdingshan and North Pingdingshan sections are well developed in the syncline

re

owing to quarry activities (Tong et al., 2004; Zhao et al., 2008). Among these three sections, the West Pingdingshan section has the best IOB record and was proposed as

lP

a candidate GSSP section for the the base of the Olenekian/IOB (Tong et al., 2004).

na

Later, Liang et al. (2011) focused on conodonts near the Smithian-Spathian boundary (SSB) of this section, making it one of the best-established sections for the Early

ur

Triassic around the world (Zhang et al., 2019).

Jo

2.1.6 Meishan section, Changxing County, Zhejiang Province (Jiang et al., 2007; Zhang et al., 2009) As the GSSP section of PTB, the Meishan section has received much attention since the 1980s (Zhao et al., 1981; Wang, 1995; Zhang et al., 1987, 1995, 2007, 2009; Jiang et al., 2007; Yuan et al., 2014; Chen et al., 2015). The strata in this section

includes Changhsing, Yinkeng, Helongshan and Nanlinghu Formations. The Changxing Formation comprises siliceous limestone, while the other formations have almost the same features at those in the Pingdingshan section. According to more than 21,000 conodont elements from the Meishan section, Jiang et al. (2007) reported the most intensive conodont sequence near the PTB. Later, Zhang et al. (2009) re-studied this section and some new occurrences of conodonts were reported, especially those

ro of

from the upper Yinkeng Formation and lower Helongshan Formation which were not considered by Jiang et al. (2007).

-p

2.2. Yangtze Carbonate Platform

re

During the Permian-Triassic transition, the Yangtze Carbonate Platform of the South China Block was situated between the Palaeotethys to the southwest and the

lP

Panthalassa to the east (Muttoni et al, 2009; Feng et al., 1997). This area is

na

characterized by shallow water sediments, such as oolites and microbialites (Xie et al., 2010; Li et al., 2015; Chen et al., 2019). In this area, six PTB sections are chosen, the

ur

Daijiagou, Liangfengya, Jianzishan, Gaohua, Yangou and Huangzhishan sections.

Jo

2.2.1 Daijiagou and Liangfengya sections, Chongqing City (Yuan and Shen 2011; Yuan et al., 2015) In Chongqing City, the Daijiagou section and the Liangfengya section are located at Dajiagou village, Beibei District and Zhongliang Hill, Beishan District, about 40 km apart respectively (Fig. 2). Both of these two sections have well exposed

Changhsing Formation and lowermost Feixianguan Formation, the former consists of limestone interbedded with clays, while the latter comprises argillaceous limestone. Relatively, the Daijiagou section has better conodont records near the PTB (Yuan and Shen 2011; Yuan et al., 2015). In the Daijiagou section, the FO of H. parvus occurs in strata lower than the negative inorganic carbon isotopes excursion, which is contrary to the Meishan and Shangsi sections (Fig. 5 in Yuan et al., 2015 and Fig. 2 in

ro of

Joachimski et al., 2012).

2.2.2 Jianzishan section, Lichuan City, Hubei Province (Bai et al., 2017)

-p

The Jianzishan section is situated in the Ruiping countryside of Lichuan City,

re

Hubei Province (Fig. 2). The Late Permian Changhsing Formation and Early Triassic Daye Formation are well exposed in this section. The underlying Changhsing

lP

Formation consists of thick-bedded bio-clastic limestone and the overlying Daye

na

Formation is characterized by thick-bedded microbialites and medium-bedded limestone alternating with yellow shale. In this PTB section, H. parvus is reported

ur

from the lowermost part of microbialites (Bai et al., 2017).

Jo

2.2.3 Gaohua section, Cili County, Hunan Province (Wang et al., 2016) The Gaohua section is located in the southwest part of Cili county, Changde City,

Hunan Province. During the Permian-Triassic transition, skeletal packstones of the topmost Changhsing Formation and micobialites and oolites of the lowermost Daye Formation were developed. There is a hiatus between these two formations, where the

FO of H. parvus was reported (Wang et al., 2016).

2.2.4 Yangou section, Leping County, Jiangxi Province (D. Y. Sun et al., 2012) This section in Leping County, Jiangxi Province is about 400 km from the Meishan section (Fig. 2). The latest Permian Changhsing Formation and the earliest Triassic Daye Formation are developed here.

The Yangou section represents a

ro of

typical shallow carbonate sequence with abundant ostracod fossils in non-microbialite facies (Qiu et al., 2019). There are also abundant conodont fossils reported, which

indicates that the FO of H. parvus occurs below the negative carbon isotope peak (D.

-p

Y. Sun et al., 2012; Qiu et al., 2019). It is noteable that oolites are developed in the

re

basal part of the Daye Formation, which indicates that some strata might be missing

lP

in this section.

na

2.2.5 Huangzhishan section, Huzhou City, Zhejiang Province (Chen et al., 2008) The Huangzhishan section is located about 17 km northwest of Huzhou City,

ur

Zhejiang Province, and approximately 30 km from the Meishan section (Fig. 2). In this section, the latest Permian Changhsing Formation is mainly composed of

Jo

limestone with rare chert. Thus, the Changhsing Formation in the Huangzhishan section indicates an outer carbonate platform environment which is shallower than the Meishan section. What’s more, the conodonts from this section provide important supplementary data for the Meishan section, owing to it being three times thicker than the Meishan section (Chen et al., 2008).

2.3. Nanpanjiang Basin The Nanpanjiang Basin is located on the southwestern margin of South China. During the Early Triassic, thick deep-water sediments with abundant marine fossils were deposited. Moreover, several isolated carbonate platforms also developed during this interval, with related rapid changes in facies (Yin et al., 2014). For this study, we

ro of

selected 16 sections from the Nanpanjiang Basin.

2.3.1. Qingyan section, Guiyang City, Guizhou Province (Ji et al., 2011)

-p

The Qingyan section (consisting of three sub-sections, namely

re

Jiuyuanjing-Xiabaituo, Yingpanpo-Mafengpo and Yingshangpo-Leidapo) is situated in the Huaxi District, 30 km south of Guiyang, Guizhou Province (Fig. 2). In

lP

ascending order, the Changhsing Formation of Permian age and the Shabaowan,

na

Luolou, Anshun, and Qingyan Formations of Triassic age are well exposed in this section. The Changhsing Formation comprises massive bioclastic limestone, cherty

ur

limestone and mudstone. The Shabaowan Formation consists of mudstone, the Luolou Formation is characterized by limestone, argillaceous limestone, mudstone and

Jo

breccia. The Anshun Formation is composed of dolomite and interbedded brecciated limestone and the Qingyan Formation is composed of thin-bedded limestone and mudstone. Conodont fossils (Ji et al., 2011) recovered from this section are mainly distributed in the Olenekian-Anisian boundary (OAB).

2.3.2. Jiarong section, Huishui County, Guizhou Province (Chen et al., 2015) This section is located about 20 km south of Huishui County, Guizhou Province. In ascending order, the Upper Permian Dalong Formation and the Lower Triassic Luolou and the Ziyun formations are well exposed along a road in the Jiarong section. As one of the best documented sections for Smithian and Spathian conodonts within the Nanpanjiang Basin, the conodonts from this section have been used for UAZ

ro of

analyses to make correlations around Tethys near the Smithian-Spathian boundary (SSB) (Chen et al., 2013, 2015, 2019).

-p

2.3.3. Mingtang section, Luodian County, Guizhou Privince (Liang et al., 2016)

re

The Mingtang section is located 4.5 km west of Bianyang Town, Luodian County, Guizhou Province (Fig. 2). During the Permian-Triassic transition, the Dalong,

lP

Luolou and Poduan formations were developed here. The Dalong Formation is

na

composed of black-grayish thin-bedded siliceous mudstone with ammonoids, brachiopods and bivalves. The Luolou Formation is dominated by mudstone in its

ur

lower part which indicates a low-energy inter-shelf basin environment, and limestone intercalated with brecciated limestone at its upper part, which indicates deposition on

Jo

the slope. The Poduan Formation is characterized by thick-bedded Tubiphytes boundstone and grainstone with interbeds of brecciated limestone, which indicates a platform margin setting with reef complex. Conodonts from this section are mainly distributed near the OAB, which is recognized by the FO of Chiosella timorensis (Liang et al., 2016).

2.3.4 Gaimao section, Guiyang City, Guizhou Province (Yang et al., 2012) This section is located on a hillside, 100 m east of Gaimao village, Huaxi District, Guiyang City, Guizhou Province. Bioclastic limestone of the Changhsing Formation, carbonaceous chert of the Dalong Formation and calcareous mudstone of the Shabaowan Formation are developed here. Although the FO of H. parvus in this

ro of

section lies within the Shabaowan Formation, the occurrences of Isarcicella isarcica and I. staeschei in the underlying strata indicate that the PTB is within the Dalong

-p

Formation (Yang et al., 2012).

re

2.3.5. Sidazhai and Ganheqiao sections, Guizhou Province (Liang et al., 2017) The Sidazhai section is located at Sidazhai village, approximately 50 km south of

lP

the Ziyun County, while the Ganheqiao section is located 7 km north of Wangmo

na

County (Fig. 2). During the Permian, a narrow intraplatform basin developed in southwest Guizhou in the area between Ziyun and Wangmo Counties, and these two

ur

sections are developed here (Lehrmann et al., 2015a; Liang et al., 2017). The Luolou, Ziyun, Xinyuan Formations are represented in both of these two sections. In the

Jo

Sidazhai section, the Linghao Formation of the latest Permian is also exposed and the Luolou Formation is better exposed providing better conodont records for the Early Triassic. In addition, the Ganheqiao section is also important for its conodonts from the OAB (Liang et al., 2017).

2.3.6. Dajiang and Dawen sections, Luodian County, Guizhou Province (Liu et al., 2007; Chen et al., 2009; Jiang et al., 2014 ) The Dajiang and Dawen sections are located in the interior of the Great Bank of Guizhou (GBG), and about 2 km from each other. These two sections have similar strata and similar conodont records (Liu et al., 2007; Jiang et al., 2014). What is noticeable is that the studies from the Dawen section have different interpretations for

from Chen et al. (2009) but not from Liu et al. (2007).

ro of

the PTB (Liu et al., 2007; Chen et al., 2009) and Brosse et al. (2016) utilized data

-p

2.3.7. Guandao and Bianyang sections, Luodian County, Guizhou Province (Yan et al.,

re

2013; Lehrmann et al, 2015b)

The Guandao section occurs on the basin-margin of the northern flank of the

lP

GBG (Fig. 2). The Wuchiaping, Dalong, Luolou and Xinyuan formations are

na

developed in ascending order. In particular, several thin volcanic ash units occur in the Luolou Formation and bracket the OAB. After the report of conodont fossils, this

ur

section attracted much attention for its good record near the OAB (Wang et al., 2005). Recently, Lhermann et al. (2015b) reported an integrated study including conodont

Jo

biostratigraphy from this section. The Bianyang section is located 2 km north of the Guandao section, but it

represents a deeper water environment. The Dalong and Luolou formations of this section contain more mudstone, and the condonts from this section have better records during the Olenekian than those from the Induan (Yan et al., 2013).

2.3.8. Pojue, Dala and Taiping sections, Baise City, Guangxi Province (Y. Chen et al., 2019; Xiao et al., 2018b) These sections are located on two other different isolated carbonate platforms in the Nanpanjiang Basin (Fig. 2). During the Late Permian, medium-bedded bioclastic limestone with abundant microfossils of the Heshan Formation developed at these

ro of

sections (Tian et al., 2018; Xiao et al., 2018b). After the end-Permian mass extinction, which is marked by a hiatus, thick-bedded microbialites of the lowermost Majiaoling

Formation developed. The FOs of H. parvus from the Taiping and Dala sections lie at

re

(Y. Chen et al., 2019; Xiao et al., 2018b).

-p

the base of the microbilaites, while it lies within the microbialites at the Pojue section

na

2015; Wu et al., in press)

lP

2.3.9 Wuzhuan and Motianling sections, Baise City, Guangxi Province (Brosse et al.,

The Wuzhuan and Motianling sections are both located on the margins of two

ur

isolated carbonate platforms in the Nanpanjiang Basin during the Early Triassic (Fig. 2). The uppermost Permian strata of these two sections are all composed of

Jo

medium-bedded bioclastic limestone. After the end-Permian regression, microbialites of the Luolou Formation developed (Yin et al., 2014). However, in the Motianling section, the Luolou Formation is also characterized by banded argillaceous limestone in its upper part and eleven conodont interval zones are established there according to 2244 conodont P1 elements (Wu et al., in press).

Brosse et al. (2015) reported conodonts near the PTB at the Wuzhuan section. Due to the earlier FO of H. parvus than the FO of H. eurypyge in this section, they argued that the FO of H. parvus in the Meishan section did not correspond to its FAD. The problem is that this conclusion was made on the assumption that the impact of local ecological changes at Wuzhuan section could be eliminated because of the invariance of microfacies and sedimentological features and virtually constant δ13Ccarb.

ro of

Then they estimated that the FO of H. parvus was 7.5 kyr older than the ages of H. eurypyge and I. turgida in the Wuzhuan section according to modern stromatolites growth rate. However, even in a similar ecological environment, the FO of H.

-p

eurypyge is lower than the FO of H. parvus in the Dawen section, which is

re

inconsistent with the records from the Wuzhuan section (Chen et al., 2009; Brosse et al., 2016). In addition, these authors (Brosse et al., 2016) obtained a non-contradiction

lP

result (second run in their study) without changing the occurrences of H. parvus or H.

na

eurypyge, even though they insist that the records in Wuzhuan and Meishan section

ur

have contradictions (Brosse et al., 2015).

3. Material and methods

Jo

3.1 The conodont records from the Lower Triassic of South China After the establishment of the GSSP for the PTB in the Meishan D section (Yin

et al., 2001), researchers paid more attention to the conodont biostratigraphy of the Lower Triassic in South China (eg. Zhao et al., 2007; 2008; 2013; Yan et al., 2013; Chen et al., 2015; Sun et al., 2015; Liang et al., 2016; Lyu et al., 2017). In South

China, the Lower Triassic is widely distributed in the Yangtze and Nanpanjiang Basin areas, and mainly composed of carbonate and fine-grained clastic rock (Tong and Yin, 2002). After rechecking all taxonomic data with illustrated plates (Table 1), 2130 conodont occurrences from 28 sections of South China were collated from publications, involving 121 species (Fig. 2; supplementary data Table 1). The Dawen section was excluded from the metadata, owing to contradictory conodont

ro of

occurrences from two studies (Liu et al., 2007; Chen et al., 2009). On the contrary, we utilized data that Brosse et al. (2016) excluded (Chaotian, Huangzhishan, Bianyang, Zhongzhai and Daijiagou) for the reason that more data will be better for discerning

-p

the “virtual relationship” between the species when doing the analysis of UAM,

lP

3.2 Unitary association analysis

re

although these sections may have lower diversity of conodont or long-ranging taxa.

na

Due to incomplete records of fossils or sampling efforts, occurrences of any species can be discontinuous or discrete in one section and their FO or LO can be The traditional interval

ur

diachronous even in adjacent sections (Brosse et al., 2016).

zone produces a continuous result, which contradicts the discontinuous fossil record

Jo

(Guex, 1991). However, based on all occurrences of species in a local maximal horizon, the UAM is a unique deterministic mathematical model designed to generate a discrete sequence of coexistence intervals of species (Guex, 1991; Guex et al., 2016). By using the software PAST (Hammer et al., 2001), we can easily apply this method now, and several studies have been conducted, such as Permian radiolarians from low

latitudes (Xiao et al., 2018a), Devonian ammonoids from Moroco (Monnet et al., 2011), Late Permian conodonts from South China (Yuan et al., 2018), Smithian conodonts from the Tethys (Chen et al., 2016, 2019) and PTB conodonts from South China and India (Brosse et al., 2016, 2017).

ro of

4. Results 4.1 The first analysis

This first run of the raw data produced 89 residual horizons, 59 maximal cliques,

-p

31 unitary associations, 292 contradictions, 3 cliques in cycles and 1 residual virtual

re

edge with 83 species left (Fig. 3; Table 3). Our raw dataset contains 38 singletons which were eliminated under the “null endemic taxa” option in PAST. Three cliques

lP

containing species D. discreta, E. costatus, Ns. chaohuensis, Ns. cristagalli, Ns.

na

dieneri, Ns. peculiaris, Ns. sp. V, Ns. pakistanensis, Nv. ex. gr. waageni, Nv. posterolongatus and Sw. kummeli are in the cycle, among which, species Nv.

ur

posterolongatus also involved in most C3/S3/S4 circuits. So the occurrences of Nv. posterolongatus was discarded. According to the taxon counts of Z4 cycles, C.

Jo

postwangi, C. tulongensis, H. peculiaris , M. ultima, Cn. conservativa, Cr. breviramulis were also deleted. Further, owing to the large numbers of contradictions involving the species Ns. peculiaris, with this species being reported from the Pingdingshan, Guandao and Jianshi sections but not being illustrated, the occurrences of this species are also deleted. According to the biostratigraphical graph (Fig. 3), the

C3/S3 circuits mainly involved several species (C. meishanensis, Ns. dieneri, Ns. cristagalli, Nv. ex. gr. waageni and so on), so the LO of C. meishanensis is upwardly extended to the same level as the FO of Nc. discreta, the LO of C. zhangi is upwardly extended to the same level as the FOs of H. latidentatus and H. inflatus, the LO of Ns. dieneri is upwardly extended to the same level as the FO of Tr. homeri, the LO of Ns. cristagalli is upwardly extended to the same level as the FOs of

ro of

Gu.bransoni, the LO of Nv. ex. gr. waageni is upwardly extended to the same level as the FO of Tr. homeri and so on. Detailed steps are shown in the supplementary data

Jo

ur

na

lP

re

-p

Table 2.

ro of -p re lP na ur Jo

Fig. 3. The result of the first Unitary Association analysis using the initial raw dataset.. (A) Non-oriented part of the biostraigraphical graph: coexistences of the remaining 83 species; (B) oriented part of the biostraigraphical graph: superpositions of the remaining 83 species; (C) oriented part of the biostraigraphical graph: C3 cycles; (D)

Semi-oriented part of the biostratigraphical graph: S3 circuits. (E) Superposition relationships between the maximal cliques. As stated above, contradictions come from ecological effects or from different opinions about taxonomic classification (Yuan et al., 2018). To solve these problems, two solutions are used in this study: the first one is that virtual connections of species are considered according to the four forbidden sub-graphs which are extracted from

ro of

PAST (Fig. 4; Brosse et al., 2016, 2017; Chen et al., 2019); the second one is that

some ocurrences of special species need to be deleted during the run of the analysis,

Jo

ur

na

lP

re

mis-using (Yuan et al., 2018; Xiao et al., 2018a).

-p

for the reason that these data might have been influenced by over-identification and

Fig. 4. Forbidden subgraphs discerned from PAST and their solutions by adding a virtual co-occurrence between two species. (A) S3 circuit; (B) S4 circuit; (C) S4′ circuit; (D) Z4″circuit.

4.2 The last analysis After the steps, the last run on PAST produces 89 residual horizons, 42 maximal cliques, 27 unitary associations, 0 cliques in cycles, 0 residual virtual edges and 12 contradictions but no S3 circuit within the last 72 species (Fig. 5; Table 4). Further detailed work needs to be done to give us more information to find ways of solving the last 12 contradictions. So far, the present 27 unitary associations provide enhanced

ro of

conodont bio-stratigraphic comparison of the 28 sections around South China during

na

lP

re

-p

the Early Triassic (Figs. 6 and 7).

ur

Fig. 5. The result of the last Unitary Association analysis after the modifications of the original data. (A) the coexistence graph of the remaining 72 species; (B) the

Jo

superposition graph of the remaining 72 species.

ro of

Fig. 6. Sequence of Unitary Associations with taxa after the last unitary association

ur

na

lP

re

-p

analysis. Blank squares indicate discontinuities.

Jo

Fig. 7. Reproducibility matrix (UAs vs. sections matrix) of Unitary Associations.

4.3. Lateral reproducibility and the merge of UAs Biographic correlations will be more meaningful if the same unit can be discerned from different sections, which means that UAs with wider lateral

distribution will be more useful and UAs with lower lateral distribution need to be merged with their adjacent ones. The difference between adjacent UAs is termed the “lateral reproducibility”, which is further connected with “dissimilarity index” and “frequency of arcs” (Brosse, 2016; Xiao et al., 2018a). Ranging from 0 to 2, the dissimilarity index indicates the difference between the two adjacent UAs, and the score 0 means that two UAs are homogenous while the score 2 means that they are

ro of

totally different. The frequency of the arcs are used for considering how to merge the UAs. These two parameters are generated by the software PAST (Hammer et al., 2001).

-p

According to the reproducibility matrix graph (Fig. 7), UAs 23, 22, 21, 18, 17,

re

13, and 6 only exist in a single section, which indicates that these UAs need further treatment. From the graph of the sequence of UAs with taxa (Fig. 6), the UAs 23, 22,

lP

21 are Spathian in age. During the Spathian, the Sidazhai and Ganheqiao sections are

na

the only sections which might have the best conodont records among the 28 sections resulting from their deep-water facies during that time (Liang et al., 2017). We herein

ur

decide not to merge these three UAs, which is also supported by the frequency of the arcs (Fig. 7). Similarly, UAs 17, 13 and 6 are also not merged with others. We decided

Jo

to merge UA 18 with UA 19 (D = 0.3427, 0 arcs ).

4.4. Description of the UAZs The optimal result after merging UAs produces a biozonation with 26 UAZs for the 28 sections (Figs. 8―10). These UAZs are all discrete, and based on current

conodont records of the Early Triassic from South China. Future work from new sections or detailed work from these sections may change the upper or lower

-p

ro of

boundary of these zones.

Jo

ur

na

lP

re

Fig. 8. Strategies for merging Unitary Associations into Unitary Association Zones.

Fig. 9. Sequence of the resulting 26 Unitary Association Zones.

ro of -p re

Fig. 10. UAZs in studied sections. Abbreviations: D. = Dalong Formation; H.=

lP

Heshan Formation; C. = Changxing Formation; He. = Helongshan Formation; W. =

na

Wuchiaping Formation; L. = Luolou Formation; Z. = Ziyun Formation; X. = Xinyuan

ur

Formation; Fm. = Formations; Li. = Linghao Formation; An.= Anshun Formation.

4.4.1. UAZ 1

Jo

Content: C. wangi, C. parasubcarinata, C. subcarinata, C. zhangi, C. Changxingensis, H. inflatus, C. deflecta. Characteristic species: C. wangi. Age: Changhsingian Geographical distribution: Ganxi and Wuzhuan.

4.4.2. UAZ 2 Content: C. parasubcarinata, C. subcarinata, C. zhangi, C. changxingensis, H. inflatus, C. deflecta, H. pisai, H. latidentatus, H. typicalis, H. praeparvus. Characteristic pair of species: C. parasubcarinata with H. pisai, H. latidentatus, H. typicalis or H. praeparvus.

ro of

Age: Changhsingian.

Geographical distribution: Jianzishan, Wuzhuan, Huangzhishan.

-p

4.4.3. UAZ 3

re

Content: C. subcarinata, C. zhangi, C. Changxingensis, H. inflatus, C. deflecta, H. pisai, H. latidentatus, H. typicalis, H. praeparvus, C. yini, C. zhejiangensis, H.

lP

changxingensis, C. meishanensis, C. taylorae, C. carinata.

na

Characteristic pair of species: C. subcarinata with C. yini, C. zhejiangensis, H. changxingensis, C. meishanensis, C. taylorae, or C. carinata.

ur

Age: Changhsingian.

Jo

Geographical distribution: Daxiakou, Chaotian, Meishan, Shangsi.

4.4.4. UAZ 4

Content: C. zhangi, C. changxingensis, H. inflatus, C. deflecta, H. pisai, H. latidentatus, H. typicalis, H. praeparvus, C. yini, C. zhejiangensis, H. changxingensis, C. meishanensis, C. taylorae, C. carinata, H. eurypyge.

Characteristic pair of species: H. eurypyge with C. yini. Age: Changhsingian. Geographical distribution: Daijiagou, Liangfengya.

4.4.5. UAZ 5 Content: C. zhangi, C. changxingensis, H. inflatus, C. deflecta, H. pisai, H.

ro of

latidentatus, H. typicalis, H. praeparvus, C. zhejiangensis, H. changxingensis, C. meishanensis, C. taylorae, C. carinata, H. eurypyge, I. huckriedei, H. priscus, I. turgida, H. parvus, H. anterodentatus.

-p

Characteristic pair of species: C. zhangi with I. huckriedei, H. priscus, I. turgida, H.

re

parvus or H. anterodentatus. Age: Griesbachian.

4.4.6. UAZ 6

na

lP

Geographical distribution: Bianyang, Shangsi.

ur

Content: C. changxingensis, H. inflatus, C. deflecta, H. pisai, H. latidentatus, H. typicalis, H. praeparvus, C. zhejiangensis, H. changxingensis, C. meishanensis, C.

Jo

taylorae, C. carinata, H. eurypyge, I. huckriedei, H. priscus, I. turgida, H. parvus, H. anterodentatus, I. peculiaris, I. lobata, I. staeschei, H. bicuspidatus, C. planata. Characteristic pair of species: C. changxingensis with I. peculiaris, I. lobata, I. staeschei, H. bicuspidatus or C. planata. Age: Griesbachian.

Geographical distribution: Meishan.

4.4.7. UAZ 7 Content: H. inflatus, C. deflecta, H. pisai, H. latidentatus, H. typicalis, H. praeparvus, C. zhejiangensis, H. changxingensis, C. meishanensis, C. taylorae, C. carinata, H. eurypyge, I. huckriedei, H. priscus, I. turgida, H. parvus, H. anterodentatus, I.

ro of

peculiaris, I. lobata, I. staeschei, H. bicuspidatus, C. planata, I. inflata, I. isarcica, C. lehrmanni. Characteristic species: I. inflata.

-p

Characteristic pair of species: H. inflatus with I. isarcica or C. lehrmanni.

re

Age: Griesbachian.

4.4.8. UAZ 8

na

Meishan, Shansi.

lP

Geographical distribution: Wuzhuan, Daijiagou, Gaohua, Chaotian, Dala, Motianling,

ur

Content: C. deflecta, H. pisai, H. latidentatus, H. typicalis, H. praeparvus, C. meishanensis, C. taylorae, C. carinata, H. eurypyge, I. turgida, H. parvus, H.

Jo

anterodentatus, I. lobata, I. staeschei, H. bicuspidatus, C. planata, I. isarcica, C. lehrmanni, H. postparvus. Characteristic pair of species: I. lobata with H. postparvus. Age: Griesbachian. Geographical distribution: Jianzishan, Dajiang.

4.4.9. UAZ 9 Content: C. deflecta, H. latidentatus, H. typicalis, H. praeparvus, C. meishanensis, C. taylorae, C. carinata, H. eurypyge, I. turgida, H. parvus, H. anterodentatus, I. staeschei, H. bicuspidatus, C. planata, I. isarcica, C. lehrmanni, H. postparvus, C. orchardi, C. krystyni.

ro of

Characteristic species: C. orchardi.

Characteristic pair of species: C. krystyni with I. isarcica, I. staeschei, C. deflecta or H. latidentatus.

-p

Age: Griesbachian.

re

Geographical distribution: Daxiakou, Pingdingshan, Gaimao.

lP

4.4.10. UAZ 10

na

Content: H. typicalis, H. praeparvus, C. meishanensis, C. taylorae, C. carinata, H. eurypyge, I. turgida, H. parvus, H. anterodentatus, H. bicuspidatus, C. planata, C.

ur

lehrmanni, H. postparvus, C. krystyni, H. sosioensis. Characteristic species: H. sosioensis.

Jo

Age: Griesbachian.

Geographical distribution: Jiarong, Dajiang, Motianling, Sidazhai.

4.4.11. UAZ 11 Content: H. praeparvus, C. meishanensis, C. taylorae, C. carinata, H. eurypyge, H.

parvus, H. anterodentatus, C. planata, C. krystyni, Nc. discreta. Characteristic pair of species: Nc. discreta with C. krystyni, C. planata, H. parvus, H. eurypyge or C. meishanensis. Age: Griesbachian. Geographical distribution: Daxiakou, Meishan.

ro of

4.4.12. UAZ 12

Content: H. praeparvus, C. taylorae, C. carinata, H. anterodentatus, C. planata, Nc. discreta, Sw. kummeli.

-p

Characteristic pair of species: Sw. kummeli with Nc. discreta, C. planata, C. taylorae

re

or C. carinata. Age: Dienerian.

4.4.13. UAZ 13

na

lP

Geographical distribution: Daxiakou, Meishan.

ur

Content: H. praeparvus, H. anterodentatus, Sw. kummeli, Ns. dieneri. Characteristic pair of species: Ns. dieneri with H. praeparvus or H. anterodentatus.

Jo

Age: Dienerian.

Geographical distribution: Mingtang.

4.4.14. UAZ 14 Content: Sw. kummeli, Ns. dieneri, Ns. sp. V, Ns. chaohuensis, Ns. chii, Ns.

pakistanensis, D. discreta, Ns. cristagalli, Nv. ex. gr. waageni. Characteristic pair of species: Sw. kummeli with Ns. sp. V, Ns. chaohuensis, Ns. chii, Ns. pakistanensis, D. discreta, Ns. cristagalli or Nv. ex. gr. waageni. Age: Smithian. Geographical distribution: Daxiakou, Mingtang, Meishan, Ganheqiao.

ro of

4.4.15. UAZ 15

Content: Ns. dieneri, Ns. sp. V, Ns. chaohuensis, Ns. chii, Ns. pakistanensis, D. discreta, Ns. cristagalli, Nv. ex. gr. waageni, E. costatus, Ns. tongi.

-p

Characteristic pair of species: Ns. dieneri, Ns. sp. V or Ns. chaohuensis with E.

re

costatus or Ns. tongi. Age: Smithian.

4.4.16. UAZ 16

na

lP

Geographical distribution: Jianshi, Jiarong, Motianling.

ur

Content: Ns. dieneri, Ns. chii, Ns. pakistanensis, D. discreta, Ns. cristagalli, Nv. ex. gr. waageni, E. costatus, Ns. tongi, Ns. novaehollandae, E. hamadai, Pg. peculiaris.

Jo

Characteristic species: Ns. chii, E. costatus or Ns. tongi with Ns. novaehollandae, E. hamadai or Pg. peculiaris. Age: Smithian. Geographical distribution: Daxiakou, Jiarong, Motianling, Pingdingshan.

4.4.17. UAZ 17 Content: Ns. dieneri, Ns. pakistanensis, D. discreta, Ns. cristagalli, Nv. ex. gr. waageni, Ns. novaehollandae, E. hamadai, Pg. peculiaris, Nv. spitiensis. Characteristic species: Nv. spitiensis with Ns. novaehollandae, Ns. pakistanensis. Age: Smithian.

ro of

Geographical distribution: Pingdingshan.

4.4.18. UAZ 18

Content: Ns. dieneri, D. discreta, Ns. cristagalli, Nv. ex. gr. waageni, E. hamadai, Pg.

-p

peculiaris, Nv. spitiensis, Nv. pingdingshanensis, Gu. bransoni, Gu. robustus.

re

Characteristic pair of species: D. discreta, Ns. cristagalli, E. hamadai or Nv. spitiensis with Nv. pingdingshanensis, Gu. bransoni or Gu. robustus.

lP

Age: Spathian.

ur

4.4.19. UAZ 19

na

Geographical distribution: Daxiakou, Ganheqiao, Guandao, Sidazhai.

Content: Ns. dieneri, Nv. ex. gr. waageni, Pg. peculiaris, Nv. pingdingshanensis, Gu.

Jo

bransoni, Gu. robustus, Pc. obliqua. Characteristic species: Pc. obliqua. Age: Spathian. Geographical distribution: Mingtang, Bianyang.

4.4.20. UAZ 20 Content: Ns. dieneri, Nv. ex. gr. waageni, Pg. peculiaris, Nv. pingdingshanensis, Gu. bransoni, Gu. robustus, Ic. zaksi, Tr. sosioensis, Ic. collinsoni, Tr. homeri. Characteristic species: Pg. peculiaris with Ic. zaksi, Tr. socioensis, Ic. collinsoni or Tr. homeri. Age: Spathian.

ro of

Geographical distribution: Sidazhai.

4.4.21. UAZ 21

-p

Content: Ns. dieneri, Nv. ex. gr. waageni, Nv. pingdingshanensis, Gu. bransoni, Gu.

re

robustus, Ic. zaksi, Tr. sosioensis, Ic. collinsoni, Tr. homeri, Tr. brevisilmus, Nv. abruptus, Sp. spathi.

lP

Characteristic pair of species: Ic. zaksi with Tr. brevissimus, Nv. abruptus or Sp.

Age: Spathian.

na

spathi.

ur

Geographical distribution: Ganheqiao.

Jo

4.4.22. UAZ 22

Content: Ns. dieneri, Nv. ex. gr. waageni, Nv. pingdingshanensis, Gu. bransoni, Gu. robustus, Tr. sosioensis, Ic. collinsoni, Tr. homeri, Tr. brevissimus, Nv. abruptus, Sp. spathi, Ns. triangularis, Tr. symmetricus, Ns. brochus. Characteristic pair of species: Gu. bransoni or Gu. robustus with Ns. triangularis, Tr.

symmetricus or Ns. brochus. Age: Spathian. Geographical distribution: Ganheqiao.

4.4.23. UAZ 23 Content: Ns. dieneri, Nv. ex. gr. waageni, Nv. pingdingshanensis, Tr. socioensis, Ic.

ro of

collinsoni, Tr. homeri, Tr. brevisilmus, Nv. abruptus, Sp. spathi, Ns. triangularis, Tr. symmetricus, Ns. brochus, Cr. kochi.

Age: Spathian.

re

Geographical distribution: Qingyan, Sidazhai.

-p

Characteristic species: Cr. kochi.

lP

4.4.24. UAZ 24

na

Content: Ic. collinsoni, Tr. homeri, Nv. abruptus, Sp. Spathi, Ns. triangularis, Tr. symmetricus, Ns. brochus, Ns. curtatus.

ur

Characteristic species: Ns. curtatus. Age: Spathian.

Jo

Geographical distribution: Bianyang, Motianling.

4.4.25. UAZ 25 Content: Tr. homeri, Nv. abruptus, Sp. spathi, Ns. triangularis, Tr. symmetricus, Ns. brochus, Ch. gondolelloides, Ch. timorensis.

Characteristic pair of species: Ns. triangularis with Ch. gondolelloides or Ch. timorensis. Age: Anisian Geographical distribution: Mingtang, Guandao.

4.4.26. UAZ 26

gondolelloides, Ch. timorensis, Ni. kockeli, Ni. germanica.

Age: Anisian.

re

Geographical distribution: Mingtang, Guandao.

-p

Characteristic species: Ni. cockeli or Ni. germanica.

ro of

Content: Tr. homeri, Nv. abruptus, Sp. Spathi, Tr. symmetricus, Ns. brochus, Ch.

lP

5. Discussion

na

5.1. Conodont records from the Dawen section applied to UAZs The Dawen section is located within the GBG during the Permian-Triassic

ur

transition (Fig. 2). After the end-Permian regression, microbialite which is 13.14 m in thickness develops as overlying strata of bioclastic limestone in this section (Liu et al.,

Jo

2007; Chen et al., 2009; Yin et al., 2014). Owing to the low abundance of conodonts in the bioclastic limestone and microbialites in the Nanpanjiang Basin (Jiang et al., 2014; Wang et al., 2016; Wu et al., in press), two conodont studies from this section indicated different FOs of H. parvus, which further lead to different placements of the PTB (Liu et al., 2007; Chen et al., 2009). In the study of Liu et al. (2007), H. typicalis,

H. parvus, H. praeparvus, H. latidentatus, H. eurypyge, C. deflecta, C. changxingensis are reported from the basal part of the microbialites, which belong to UAZ 5 to UAZ 6 in our study; and the coexistences of H. typicalis, H. parvus, I. staeschei, I. isarcica and H. postparvus close to the top of the microbialites confine this rock unit into UAZ 8 to UAZ 9 in our study (Fig. 11). In the study of Chen et al. (2009), C. zhejiangensis, H. latidentatus, H. praeparvus, H. eurypyge, H. typicalis

ro of

(with no occurrence of H. parvus) are reported from the basal part of the microbialites, which belong to UZA 4 to 7 in our study; the coexistences of C. taylorae, C. kazi, C. lehrmanni, I. staeschei, H. postparvus confine them into UAZ 8 to UAZ 9 in our

-p

study (Fig. 11). What’s more, the basal part of the microbialite in the study of Liu et al.

re

(2007) would belong to UAZ 4 to UAZ 6 if the occurrences of H. parvus are ignored

Jo

ur

na

lP

here. Herein, the UAM make the result of these two studies comparable.

ro of -p re

na

and the discerned UAZs.

lP

Fig. 11. Conodont records from the Dawen section (Liu et al., 2007; Chen et al., 2009)

5.2. Definition of stage and sub-stage boundaries by UAZs

ur

Defined by the occurrences of characteristic species or pair of species, UAZs are discrete zones and consist of sets of species. Thus, manual examination needs to be

Jo

done to correlate these zones to the geological timescale (Xiao et al., 2018a). As a widely distributed species, the FAD of H. parvus has been used to position the GSSP for the base of the Triassic (PTB) in Meishan D section (Yin et al., 2001), and the FO of H. parvus has been used for the recognition of the PTB in many other sections (e.g. Jiang et al., 2007, 2014, 2015; Brosse et al., 2016, 2017). Thus, the PTB lies at the

base of UAZ 5 in this study. Similarly, the Griesbachian-Dinerian boundary (GDB) has been traditionally recognized by the FO of Sw. kummeli (e. g. Zhang et al., 2007; Zhao et al., 2013), which positions the GDB between UAZ 11 and UAZ 12. Although the GSSP of the IOB remains to be formally ratified, the FO of Nv. ex. gr. waageni has been shown to be a good candidate marker for the IOB in many sections, including China (Zhang et al., 2007; Zhao et al., 2008, 2013; Liang et al., 2016; Lyu

ro of

et al., 2017), Australia (Metcalfe et al., 2013), Japan (Maekewa et a., 2018), Vietnam (Komatsu et al., 2016), Canada (Orchard and Zonneveld, 2009), India (Orchard and

Krystyn, 2007) and Pakistan (Sweet, 1970). Thus, the IOB lies at the base of UAZ 14

-p

in our study. However, it is noticeable that UAZ 14 is composed of Sw. kummeli, Ns.

re

dieneri, Ns. sp. V, Ns. chaohuensis, Ns. chii, Ns. pakistanensis, D. discreta, Ns. cristagalli and Nv. ex. gr. waageni. According to Fig. 6, the co-occurrences of Ns. chii

lP

and Ns. dieneri in a sample will make it belongs to UAZ 14 or UAZ 15 in this study,

na

which means this sample belongs to Smithian. In South China, Ns. chii has only been reported from Daxiakou (Zhao et al., 2013), Motianling (Wu et al., in press), and

ur

Pingdingshan (Zhao et al., 2008). Among there three sections, there are still some samples, which include both Ns. dieneri and Ns. chii, that are lower than the FO of Nv.

Jo

ex. gr. waageni. This means that the pair occurrences of Ns. dieneri and Ns. chii could be lower than the FO of Nv. ex. gr. waageni. For example, below the FO of Nv. ex. gr. waageni in bed 24-16 of West Pingdingshan, Ns. dieneri and Ns. chii have co-occurred from bed 23-2 to bed 24-15. Resulting from some hidden relationship between other species, the UAM makes the co-occurrences of Ns. dieneri and Ns. chii

have the same level with the FO of Nv. ex. gr. waageni (Fig. 6). Herein, the IOB lies within the UAZ 14. It is notable that Ns. dieneri has been divided into 3 morphotypes on the basis of the differences in the configuration of the cusp and penultimate denticle according to the material from Chaohu (Zhao et al., 2007). Later, some studies followed this definition (e.g. Liang et al., 2016; Lyu et al., 2017) but some did not (e.g. Yan et al., 2013; Chen et al., 2015). Thus, further detail about Ns. dieneri

ro of

near the IOB may sub-divide the UAZ 14 of this study and give us more information about the IOB definition. Likewise, the SSB lies between the UAZ 18 and UAZ 17 while the OAB lies between UAZ 24 and UAZ 25 in this study, if the FOs of Nv.

-p

pingdingshanensis and Ch. timorensis are taken as the marker of the SSB and OAB

re

respectively (Liang et al., 2011; Lehrmann et al., 2015b).

lP

5.3. Discussion of the FO and FAD of H. parvus

na

As the GSSP of PTB, the Meishan D section is thought to have theoretically recorded the FAD (earliest occurrences) of H. parvus at the base of Bed 27C, and this

ur

is the only location where this definition is directly applicable (Yin et al., 2001; Henderson, 2006). Thus, the local FO of H. parvus in any other section should be

Jo

later or coeval with the Meishan D section (Fig. 1). However, several studies from South China indicated that the FOs of H. parvus in Wuzhuan, Zhongzhai and Daijiagou sections are all earlier than the FAD of H. parvus in Meishan (Yuan et al., 2014; Zhang et al., 2014; Brosse et al., 2016) while it has been accepted that the FO of H. parvus in the Shangsi section is later (Jiang et al., 2011; Yuan et al., 2018).

Relative to deep water sections, the record from shallow water sections is less complete, which can also be shown by the result of this study (Figs. 12 and 13).

5.3.1. Record from shallow water sections The phylogenetic tree of Hindeodus-Iasrcicella based on ranges of taxa in the Meishan section indicates that the “FAD” of H. parvus lies within the interval of H.

ro of

eurypyge and I. turgida (Jiang et al., 2010). However, in the microbialites of the

Wuzhuan section, the FO of H. parvus is lower than the FO of H. eurypyge and I. turgida (Brosse et al., 2015). Owing to the invariance of microfacies and

-p

sedimentological features and virtually constant δ13C carb values , Brosse et al. (2015)

re

insist that the conodont record in this interval at Wuzhuan is unaffected by local ecological changes and is more likely to represent an evolutionary rather than an

lP

ecological pattern, and then the FO of H. parvus in the Wuzhuan section is earlier

na

than the FAD of H. parvus in Meishan (Brosse et al., 2015). Also, it is noticeable that their UAZ results don’t support the earlier FO of H. parvus (Brosse et al., 2016),

ur

which is consistent with our result in this study (Fig. 12). In the Daijiagou section, the FO of H. parvus is suggested to be earlier than that

Jo

of Meishan because the FO of H. parvus in the Daijiagou section lies below the most negative δ13C carb excursion while this is the opposite in the Meishan section (Yuan et al., 2015). However, Yin et al. (2014) has stated that the end-Permian regression has caused some hiatus in shallow water sections near the PTB, which means that the most negative δ13C carb excursion in these sections is not recorded. In our study, the

UAM result indicates that the most negative δ13C carb excursion in the Daijiagou section is later than the UAZ 7, which belongs to earliest Triassic but not latest Permian as Yuan et al. (2015) stated. On the other hand, according to the results of conodont apatite oxygen isotopes (Chen et al., 2016), the FO of H. parvus in the Daijiagou section lies above the sudden decreasing of oxygen isotopes and this is also the same for the Liangfengya section (Fig. 12). In the Meishan and Shangsi section

ro of

(Joachimski et al., 2012), the sudden decreasing of oxgen isotopes is coincided with

the “event horizon” which predate the PTB (or the FAD of the H. parvus). Thus, the earlier occurrence of H. parvus in these shallow water sections are also untenable if

-p

the conodont apatite oxygen isotopes are taken as the criterion.

re

In the Zhongzhai section, H. parvus co-occurred with latest Permian Palaeofusulina sinenesis in Bed 28 while other evidence from carbon isotopes, dating,

lP

ammonoids and bivalves indicates that the PTB is at the base of Bed 30 (Metcalfe et

na

al., 2007; Zhang et al., 2014). Although our UAM result can homogenise this question, it is noticeable that the disagreement originated more from the equivocal

ur

identification of specimens in Bed 28 (Brosse et al., 2016). What’s more, the Zhongzhai section is a shallow water section that is very close to Langdai and

Jo

Zhonghe sections (within 10 and 50 km, respectively). In the Zhonghe and Langdai section, microbialites can be found at the top of the Yelang Formation (Fig. 13). In another shallow water section nearby, Jiang et al. (2014) have reported the occurrence of H. parvus from the topmost bioclastic limestone of the Wuchiaping Formation, which is close to the hiatus between the microbialites and bioclastic limestone. Due to

regression and/or acidification (Yin et al., 2014; Clarkson et al., 2015), reworking could happen and made the specimens of H. parvus in Bed 28 could have originated

ur

na

lP

re

-p

ro of

from Bed 30 in the Zhongzhai section.

Jo

Fig. 12. Comparison of UAZs among shallow water sections (Wuzhuan, Daijiagou and Liangfengya). Red arrow represents the FOs of H. parvus in sections. Carbon isotope data from Hautmann et al. (2015), Yuan et al. (2015). Oxygen isotope data from Chen et al. (2016).

ro of -p

re

Fig. 13. Microbialites from Zhonghe and Langdai sections. A) Outcrop of the

lP

Zhonghe section; B) details of the microbialites from the Zhonghe section; C) Outcrop of the Langdai section, red squares indicate the microbialites; D) details of

na

the microbialites from the Langdai section.

ur

5.3.2 . Record from deep-water sections

Jo

As stated above, deep-water sections have better sedimentary records than shallow water sections. Brosse et al. (2016) first used the UAM to analyze the PTB conodont records from 6 sections of South China, including Wuzhuan, Dajiang, Dawen, Shangsi, Yangou, Meishan. Relying on the earliest occurrence of H. parvus among these sections, their result suggested that the real FO of H. parvus in the Meishan section could be at the base of Bed 27a (Fig. 10 in Brosse et al., 2016). In

addition, they do not show the earliest occurrence of H. parvus among these sections, although the Wuzhuan section has been suggested to have this record (Brosse et al., 2015, 2016). Indeed, this is because their result mostly comes from shallow water sections which leads to the absence of UAZ 3 in other sections except for Meishan. Likewise, if the FO of H. parvus in South China is taken as the PTB reference, results show that the Bianyang and Shangsi sections have the same PTB as suggested

ro of

by previous studies (Jiang et al., 2011, 2015), while the FO of H. parvus in the

Meishan section could be downwardly extended to Bed 27b (Fig. 14). It is noticeable that the PTB in the Shangsi section is not recognised by the FO of H. parvus, but by

-p

the changeover from Clarkina-dominated to Hindoedus-dominated conodont biota

re

(Jiang et al., 2011; Yuan et al. 2018). This changeover has also been widely found in South China, including Meishan (Lai et al., 2001; Yuan et al., 2014), Chaotian (Ji et

lP

al., 2007), Huangzhishan (Chen et al., 2008), Liangfengya (Yuan and Shen, 2011),

na

Dajiang (Jiang et al., 2014), Bianyang (Jiang et al., 2015), and Daijiagou (Yuan et al., 2015).

ur

However, H. parvus has different FOs in the UAZs from these sections (Fig. 14). It lies at the base of the UAZ 5 in the Bianyang section, upper part of UAZ 5 in the

Jo

Shangsi section, and UAZ 6 in the Meishan section. Thus, the FO of H. parvus in Bianyang is earlier than those in Shangsi and Meishan, and the FO of H. parvus at Bianyang could be the FAD (earliest occurrence) of H. parvus in South China. The Bianyang section is located on the margin of GBG and very close to the basin facies during the Permian-Triassic transition (Yan et al., 2013; Tian et al., 2014;

Jiang et al., 2015). The environment in the Bianyang section provided a refuge zone for the organisms before the final extinction in this section, which lead to a delayed end-Permian extinction of foraminifers (Jiang et al., 2015). Also, such a special environment could have provided the environment for the earlier occurrences of H. parvus. Coincidentally, as a major group near the PTB, anchignathodontid conodonts (represented by Hindeodus and Isarcicella) is thought to have become extinct in the

ro of

late Griesbachian (Orchard, 2007), but they have co-occurrences with Ns. dieneri in the Mingtang section (Fig. 3 in Liang et al., 2016), while the latter of which is a

typical Dienerian species. Geographically, the Bianyang and Mingtang sections are

-p

separated by less than 2 km while the sedimentary characters indicate that the

re

Mingtang section is closer to the basin area (Liang et al., 2016). Thus, the habitable zone from the Mingtang and Bianyang sections could have controlled the earlier

lP

occurrences and later disappearance of anchignathodontid conodonts.

na

However, it is also noticeable that UAM relies on “temporally short sampling” data which can help to determine the real relationships of occurrences between

ur

species (Xiao et al., 2018a). At the PTB of the Meishan section, conodont elements from bed 27 are reported by sub-beds, which make the data from there “temporally

Jo

shortest” (Jiang et al., 2007). Recognized by the FO of H. parvus, the PTB lies at the base of bed 6 in the Bianyang section (Jiang et al., 2015). In this section, conodonts are reported from 4 samples and only 1 from the Triassic, and this Triassic sample represents bed 6, which further means potential mixed relationship of occurrences of conodont elements in this sample (Fig. 2 in Jiang et al., 2015). Thus, the earlier

occurrence of H. parvus in the Bianyang section also needs further detailed work

ro of

similar to that for the Meishan section.

Fig. 14. Comparison of the UAZs among deep water sections (Bianyang, Meishan,

-p

Shangsi). Red arrow represents the FOs of H. parvus in sections. Data of Bianyang

re

section from Jiang et al. (2015). Data of Meishan and Shangsi secions from

lP

Joachimski et al. (2012)

na

5.4. Comparison with carbon isotopes

Following the end-Permian mass extinction, carbonate inorganic carbon isotopes

ur

experienced secular changes due to global changes of the ecosystem (Payne et al., 2004; Sun et al., 2012; Meyer et al., 2013; H. Y. Song et al., 2013) and could be used

Jo

for correlation of the stratigraphy around South China (Payne et al., 2004; Tong et al., 2007; Yin et al., 2012) or even the world (Horacek et al., 2009; Clarkson et al., 2013; Metcalfe et al., 2013; Chen et al., 2019; Leu et al., 2019; Zhang et al., 2019). For example, the IOB, and the Smithian are coupled with positive and negative excursions, respectively (Payne et a., 2004; Horacek et al., 2007; Tong et al., 2007; Metcalfe et al.,

2013; H. Y. Song et al., 2013). Thus, the carbon isotopes of the Early Triassic are an important proxy for recognition of boundaries (e.g. Horacek et al., 2010; Yuan et al., 2015). However, the UAZs do not correlate well with the carbon isotopes (Fig. 15) (Brosse et al., 2016; Chen et al., 2019). Recently, Chen et al. (2019) applied the conodont records from Oman, Slovenia and South China into UAM, and 7 UAZs

ro of

were acquired. Comparison with the carbon isotopes indicates that the UAZs are

coupled with different characteristic of carbon isotopes changes. For example, the

maximum of the positive excursion near the SSB occurs in the UAZ 3 of Slovenia and

-p

occurs in the UAZ 4 of Oman, while it occurs between the UAZ 4 and UAZ 7 in

re

South China which resulted from the absence of UAZ 5 and UAZ 6 in the Jiarong section. What’s more, the conodont fauna represented by UAZ 7 in South China is

lP

thought to have occurred earlier and then migrated to Oman and then later to western

na

Tethys. Likewise, Brosse et al. (2016) reported 6 UAZs by synthesizing conodont records from 6 PTB sections of South China, and these UAZs do not show uniform

ur

patterns of carbon isotope changes in different sections. Similarly, the UAZs near the IOB also show different details of carbon isotopes changes in South China, but it is

Jo

difficult to make more correlations between UAZs in this study and the published carbon isotope data (Fig. 14). In reality, the discrepancy between carbon isotopes and UAZs is mainly caused by the fact that UAM only considers the first occurrence and the last occurrences of species. Thus, as stated above, owing to the ecological control or biogeographical

barriers, species could have different temporal occurrences in different areas, which further leads to different UAZs even in a geographically close area. This is a problem for all biozonations, and UAZs can reduce this effect but they cannot eliminate it. During the Early Triassic, deposition in South China, Oman and Alps are mainly carbonate with different facies, which leads to a relatively more complete carbon

Jo

ur

na

lP

re

-p

ro of

isotope record by comparison to the conodont record in some sections.

Fig. 15. Stratigraphic columns, conodont ranges, biostratigraphical correlations and carbonate carbon isotopes from West Pingdingshan (Zuo et al., 2006), Bianyang (H. Y. Song et al., 2013), Jiarong (Chen et al., 2013) and Mingtang sections (Liang et al., 2016). Abbreviations: C. = Changhsingian; D. = Dienerian; 1 = Clarkina

changxingensis; 2 = C. yini; 3 = C. meishanensis; 4 = Hindeodus changxingensis; 5 = H. parvus; 6 = Isarcicella staeschei; 7 = I. isarcica; 8 = Neoclarkina krystyni; 9 = Nc. discreta; 10 = Neospathodus dieneri.

5.5. Limitations of the UAZ Recognized by the FAD of H. parvus in the Meishan D section, the GSSP of the

ro of

PTB is located at the base of Bed 27c (Yin et al., 2001). Although some studies have proposed an earlier occurrence of H. parvus in several sections from South China

(Zhang et al., 2014; Yuan et al., 2015; Brosse et al, 2016), our study indicates that all

-p

these conclusions need more attention. Also, this boundary exhibits extinctions (H. J.

re

Song et al., 2013), abrupt changes of carbon and oxygen isotopes (Joachimiski et al., 2012), regression (Yin et al., 2014), numerical ages (Burgess et al., 2014), magnetic

lP

polarity changes (Hounslow and Muttoni, 2010) and so on. Combining all these

na

together, the GSSP of PTB is ratified and settled as the “golden spike” in the middle of Bed 27 in the Meishan D section (Yin et al., 2001).

ur

Due to the ecological control and sampling bias, same taxa would have different times of occurrences in different sections (Fig. 16). Thus, owing to the FOs of 3

Jo

different species in these sections, the UAZ recognized from these sections relying on the distribution of these 3 species would have different time intervals (Fig. 16). In addition, UAZs are determined by the occurrences of a characteristic species, which make them discrete (discontinuous). Based on the FAD of index fossils, the stage boundaries can be discerned between the UAZ or within the UAZ. However, owing to

the fact that the same UAZ in different sections would have different time intervals (Fig. 16) and no UAZ can be discerned even from some strata which contains fossils that can be used for interval zones (Fig. 11 in Brosse et al., 2016), UAZ provided us a higher resolution for us to correlate the fossil group, but not a higher accuracy to correlate the bio-stratigraphy (Chen et al., 2019). There is clear advantage of using UAZs together with Interval Zones to determine which FOs are good for correlation

ro of

and which are less good which then feeds into decisions made on which taxa to utilize for recognition of new GSSPs (Brosse et al., 2016; Xiao et al., 2018a).

It is also noticeable that the UAZs result from Brosse et al. (2016) has lower

-p

“resolution” than the conventional interval zones, as is also pointed out by Jiang et al.

re

(2017). On the contrary, by using the Early Triassic conodont records of South China, we established more UAZs in the entire Early Triassic but fewer UAZs near the PTB

lP

than the interval zones established by previous study (Fig. 9, Jiang et al., 2007, 2011).

na

In fact, this is mainly caused by the evolutionary speed of the conodont elements and the composition of the UAZ. Firstly, as concluded by Orchard (2007), conodonts

ur

evolved fast near the PTB and parallel hindeodid and gondolellid conodont interval zones can be discerned during this interval (ca. 60 ka) in many sections (e.g. Jiang et

Jo

al., 2007, 2011; Wu et al., 2014), which futher implies that many condont elements might have first occurred/evolved at the same time near the PTB (with respect to the “resolution” determined by sampling). Although the fact that there are other intervals (such as SSB) during the Early Triassic when condont elements also evolved fast, the entire Early Triassic is about 5 Mys (Galfetti et al., 2007; Burgess et al., 2014) and the

conodont elements didn’t maintain the same evolutionary speed as they did near the PTB. Therefore, more non-cooccurrences (superposition relationship) of conodonts can be discerned under the longer intervals. Secondly, since that UAZ is determined by the co-occurrence of characteristic species, more non-cooccurrences of species will increase the number of UAZs in the given time interval. Herein, UAZ has a lower

re

-p

ro of

“resolution” near the PTB or the SSB both in Brosse et al. (2016) and this study.

lP

Fig. 16. UAZ recognized from 3 sections relying on the distribution of 3 species. T

ur

6. Conclusions

na

represents time.

1. Relying on 72 conodont species, we recognized 26 UAZs through the conodont

Jo

record of 28 sections in South China from latest Permian to earliest Middle Triassic, which provide us a higher resolution quantitative biostratigraphic correlation for the conodont record from the South China region. 2. These UAZs consist of characteristic species and stage boundaries can be identified based on the FOs of corresponding species, which are also used for defining interval

zones. 3. Previous studies from shallow water sections, including Wuzhuan, Zhongzhai, and Daijiagou, recorded earlier occurrences of H. parvus than in the Meishan section, but our study does not unequivocally support this. Our study also indicates that the same PTB as Jiang et al. (2011) suggested and the FO of H. parvus is more than 2 m above the PTB.

ro of

4. Our study indicates that the Bianyang section records the earliest occurrences of H. parvus in South China, and this is coupled with a later disappearance of

anchignathodontid (Hindoedus) conodonts from the nearby Mingtang section. Thus,

-p

the environment which is similar for Bianyang and Mingtang sections could have

re

provided a sustained habitable zone for anchignathodontids. However, this conclusion requires further detailed work because of the reliance on “spot” (temporally short

lP

sampling) data by the UAM.

na

5. UAZs are defined by the occurrences of a set of species, which are further affected by ecology, so they are discrete and hard to correlate with carbon isotope curves.

ur

6. UAZs can provide us a good solution to correlate the conodont fossil group between sections or regions. In addition, with the help of FOs of index fossils, they

Jo

can be used for recognizing chronostratigraphic boundaries, but they are not able to define those boundaries precisely.

Declaration of interests The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:

Acknowledgements This study is supported by the National Natural Science Foundation of China [grant numbers 41530104, 41602024, 41661134047], the international exchange programme funded by the postgraduate school of CUG (to Kui Wu) and Fundamental

ro of

Research Funds for the Central Universities (CUGCJ1816) to China University of Geosciences (Wuhan). Martyn Golding, an anonymous reviewer and ESR editor

André Strasser are acknowledged for their inciteful reviews and constructive and

-p

helpful comments that significantly improved the paper. Ian Metcalfe acknowledges

re

support from the Australia Research Council. We are also grateful to Dr. Daoliang Chu for his help in the field and Dr. Luke Milan for his help at University of New

Jo

ur

na

lP

England.

References Aldridge, R. J., Briggs, D. E., Clarkson, E. N., Smith, M. P., 1986. The affinities of conodonts―new evidence from the Carboniferous of Edinburgh, Scotland. Lethaia 19(4), 279–291. Bai, R. Y., Dai, X., Song, H. J., 2017. Conodont and ammonoid biostratigraphies around the Permian-Triassic boundary from the Jianzishan of South

ro of

China. Journal of Earth Science 28(4), 595–613.

Bambach, R. K., Knoll, A. H., Sepkoski, J. J., 2002. Anatomical and ecological

constraints on Phanerozoic animal diversity in the marine realm. Proceedings of

-p

the National Academy of Sciences 99(10), 6854–6859.

re

Bond, D. P., Wignall, P. B., 2010. Pyrite framboid study of marine Permian–Triassic boundary sections: a complex anoxic event and its relationship to

lP

contemporaneous mass extinction. Geological

Society of America

na

Bulletin 122(7–8), 1265–1279.

Brayard, A., Escarguel, G., Bucher, H., Monnet, C., Brühwiler, T., Goudemand, N.,

ur

Galfetti, T., Guex, J., 2009. Good genes and good luck: ammonoid diversity and the end-Permian mass extinction. Science 325(5944), 1118–1121.

Jo

Brosse, M., Baud, A., Bhat, G. M., Bucher, H., Leu, M., Vennemann, T., & Goudemand, N., 2017. Conodont-based Griesbachian biochronology of the Guryul Ravine section (basal Triassic, Kashmir, India). Geobios 50(5–6), 359– 387. Brosse, M., Bucher, H., Bagherpour, B., Baud, A., Frisk, Å. M., Guodun, K.,

Goudemand, N., 2015. Conodonts from the Early Triassic microbialite of Guangxi (South China): implications for the definition of the base of the Triassic System. Palaeontology 58(3), 563–584. Brosse, M., Bucher, H., Goudemand, N., 2016. Quantitative biochronology of the Permian–Triassic boundary in South China based on conodont unitary associations. Earth-Science Reviews 155, 153–171.

ro of

Burgess, S. D., Bowring, S., Shen, S. Z., 2014. High-precision timeline for Earth’s

most severe extinction. Proceedings of the National Academy of Sciences 111(9), 3316–3321.

-p

Chen, J., Beatty, T. W., Henderson, C. M., Rowe, H., 2009. Conodont biostratigraphy

re

across the Permian–Triassic boundary at the Dawen section, Great Bank of Guizhou, Guizhou Province, South China: implications for the late Permian

lP

extinction and correlation with Meishan. Journal of Asian Earth Science 36, 442–

na

458.

Chen, J., Henderson, C. M., Shen, S. Z., 2008. Conodont succession around the

ur

Permian-Triassic boundary at the Huangzhishan Section, Zhejiang and its stratigraphic correlation. Acta Palaeontologica Sinica 47(1), 91–114.

Jo

Chen, Y., Ye, Q., Jiang, H. S., Wignall, P. B., Yuan, J. L., 2019. Conodonts and Carbon Isotopes during the Permian-Triassic Transition on the Napo Platform, South China. Journal of Earth Science 30(2), 244–257. Chen, Y. L., Jiang, H. S., Lai, X. L., Yan, C. B., Richoz, S., Liu, X. D., Wang, L. N., 2015. Early Triassic conodonts of Jiarong, Nanpanjiang Basin, southern Guizhou

Province, South China. Journal of Asian Earth Sciences 105, 104–121. Chen, Y. L., Richoz, S., Krystyn, L., Zhang, Z. F., 2019. Quantitative stratigraphic correlation of Tethyan conodonts across the Smithian-Spathian (Early Triassic) extinction event. Earth-Science Reviews, In press. Chen, Y. L., Twitchett, R. J., Jiang, H. S., Richoz, S., Lai, X. L., Yan, C. B., Sun, Y. D., Liu, X. D., Wang, L. N., 2013. Size variation of conodonts during the Smithian–

ro of

Spathian (Early Triassic) global warming event. Geology 41(8), 823–826.

Chen, Z. Q., Benton, M. J., 2012. The timing and pattern of biotic recovery following the end-Permian mass extinction. Nature Geoscience 5(6), 375.

-p

Chen, Z. Q., Tu, C. Y., Pei, Y., Ogg, J., Fang, Y. H., Wu, S. Q., Feng, X. Q., Huang, Y.

re

G., Guo, Z., Yang, H., 2019. Biosedimentological features of major microbe-metazoan transitions (MMTs) from Precambrian to

lP

Cenozoic. Earth-Science Reviews 189, 21–50.

na

Chen, Z. Q., Yang, H., Luo, M., Benton, M. J., Kaiho, K., Zhao, L. S., Huang, Y. G., Zhang, K. X., Fang, Y. H., Jiang, H. S., Qiu, H., Li, Y., Tu, C. Y., Shi, L., Zhang,

ur

L., Feng, X. Q., Chen, L., 2015. Complete biotic and sedimentary records of the Permian–Triassic transition from Meishan section, South China: ecologically

Jo

assessing mass extinction and its aftermath. Earth-Science Reviews 149, 67–107.

Clarkson, M. O., Kasemann, S. A., Wood, R. A., Lenton, T. M., Daines, S. J., Richoz, S., Ohnemueller, F., Meixner, A., Poulton, S. W., Tipper, E. T., 2015. Ocean acidification and the Permo-Triassic mass extinction. Science 348(6231), 229– 232.

Clarkson, M. O., Richoz, S., Wood, R. A., Maurer, F., Krystyn, L., McGurty, D. J., Astratti, D., 2013. A new high-resolution δ13C record for the Early Triassic: insights from the Arabian Platform. Gondwana Research 24(1), 233–242. Dai, X., Song, H. J., Wignall, P. B., Jia, E. H., Bai, R. Y., Wang, F. Y., Chen, J., Tian, L., 2018. Rapid biotic rebound during the late Griesbachian indicates heterogeneous recovery patterns after the Permian-Triassic mass

ro of

extinction. Geological Society of America Bulletin 130(11–12), 2015–2030. Erwin, D. H., 1994. The Permo-Triassic extinction. Nature 367(6460), 231.

Feng, Z. Z., Bao, Z. D., Li, S. W., 1997. Lithofacies Paleogeography of Middle and

-p

Lower Triassic of South China. Petroleum Industry Press: Beijing; (in Chinese

re

with English abstract).

Galfetti, T., Bucher, H., Ovtcharova, M., Schaltegger, U., Brayard, A., Brühwiler, T.,

lP

Goudemand, N., Weissert, H., Hochuli, P., Cordey, F., Kuang, G. D., .2007.

na

Timing of the Early Triassic carbon cycle perturbations inferred from new U–Pb ages and ammonoid biochronozones. Earth and Planetary Science Letters, 258,

ur

593–604.

Goudemand, N., Orchard, M. J., Urdy, S., Bucher, H., Tafforeau, P., 2011.

Jo

Synchrotron-aided reconstruction of the conodont feeding apparatus and implications for the mouth of the first vertebrates. Proceedings of the National Academy of Sciences 108(21), 8720–8724.

Goudemand, N., Romano, C., Leu, M., Bucher, H., Trotter, J. A., Williams, I. S., 2019. Dynamic interplay between climate and marine biodiversity upheavals during the

early Triassic Smithian-Spathian biotic crisis. Earth-Science Reviews, In press. Grasby, S. E., Beauchamp, B., Embry, A., Sanei, H., 2013. Recurrent Early Triassic ocean anoxia. Geology 41(2), 175–178. Grasby, S. E., Beauchamp, B., Knies, J., 2016. Early Triassic productivity crises delayed recovery from world’s worst mass extinction. Geology 44(9), 779–782. Guex, J., 1991. Biochronological Correlations, pp. 252, Springer Verlag, Berlin.

ro of

Guex, J., Galster, F., Hammer, Ø., 2016. Discrete biochronological time scales. Springer International Publishing, pp. 160.

Hammer, Ø., Harper, D. A., Ryan, P. D., 2001. PAST: paleontological statistics

-p

software package for education and data analysis. Palaeontologia electronica 4(1),

re

9.

Harnik, P. G., Lotze, H. K., Anderson, S. C., Finkel, Z. V., Finnegan, S., Lindberg, D.

lP

R., Liow, L., H., Lockwood, R., McClain, C. R., Mcguire, J. L, O′Dea, A,

na

Pandolfi, J. M., Simpson, C., Tittensor, D. P., 2012. Extinctions in ancient and modern seas. Trends in Ecology & Evolution 27(11), 608–617.

ur

Henderson, C. M., 1997. Uppermost Permian conodonts and Permian-Triassic boundary in the western Canada sedimentary basin. Bulletin of Canadian

Jo

Petroleum Geology 45(4), 693–707.

Henderson, C. M., 2006. Beware of your FO and be aware of the FAD. Permophiles 47, 8-9. Horacek, M., Koike, T., Richoz, S., 2009. Lower Triassic δ13C isotope curve from shallow-marine carbonates in Japan, Panthalassa realm: Confirmation of the

Tethys δ13C curve. Journal of Asian Earth Sciences 36(6), 481–490. Horacek, M., Richoz, S., Brandner, R., Krystyn, L., Spötl, C., 2007. Evidence for recurrent changes in Lower Triassic oceanic circulation of the Tethys: The δ13C record from marine sections in Iran. Palaeogeography, Palaeoclimatology, Palaeoecology 252(1–2), 355–369. Hounslow, M. W., Muttoni, G., 2010. The geomagnetic polarity timescale for the

ro of

Triassic: linkage to stage boundary definitions. Geological Society, London, Special Publications 334(1), 61–102.

Ji, W. T., Tong, J. N., Zhao, L. S., Zhou, S. Q., Chen, J., 2011. Lower–Middle Triassic

-p

conodont biostratigraphy of the Qingyan section, Guizhou province, Southwest

re

China. Palaeogeography, Palaeoclimatology, Palaeoecology 308(1–2), 213–223. Ji, Z. S., Yao, J. X., Isozaki, Y., Matsuda, T., Wu, G. C., 2007. Conodont

lP

biostratigraphy across the Permian–Triassic boundary at Chaotian, in Northern

39-55.

na

Sichuan, China. Palaeogeography, Palaeoclimatology, Palaeoecology 252(1–2),

ur

Jiang, H. S., Joachimski, M. M., Wignall, P. B., Zhang, M. H., Lai, X. L., 2015. A delayed end-Permian extinction in deep-water locations and its relationship to

Jo

temperature trends (Bianyang, Guizhou Province, South China). Palaeogeography, palaeoclimatology, palaeoecology 440, 690–695.

Jiang, H. S., Lai, X. L., Luo, G. M., Aldridge, R., Zhang, K. X., Wignall, P., 2007. Restudy of conodont zonation and evolution across the P/T boundary at Meishan section, Changxing, Zhejiang, China. Global and Planetary Change 55(1–3), 39–

55. Jiang, H. S., Lai, X. L., Sun, Y. D., Wignall, P. B., Liu, J. B., Yan, C. B., 2014. Permian-Triassic conodonts from Dajiang (Guizhou, South China) and their implication for the age of microbialite deposition in the aftermath of the end-Permian mass extinction. Journal of Earth Science 25(3), 413–430. Jiang, H. S., Lai, X. L., Yan, C. B., Aldridge, R. J., Wignall, P., Sun, Y. D., 2011.

ro of

Revised conodont zonation and conodont evolution across the Permian–Triassic boundary at the Shangsi section, Guangyuan, Sichuan, South China. Global and Planetary Change 77(3–4), 103–115.

-p

Joachimski, M. M., Lai, X. L., Shen, S. Z., Jiang, H. S., Luo, G. M., Chen, B., Chen,

re

J., Sun, Y. D., 2012. Climate warming in the latest Permian and the Permian-Triassic mass extinction. Geology 40(3), 195–198. T., Naruse,

H., Shigeta,

Y., Takashima, R., Maekawa, T.,

lP

Komatsu,

na

Dang, T. H., Dinh, C. T., Nguyen, D. P., Nguyen, H. H., Tanaka, G., Sone, M., 2014. Lower Triassic mixed carbonate and siliciclastic setting with

ur

Smithian-Spathian anoxic to dysoxic facies, An Chau basin, northeastern Vietnam. Sedimentary Geology 300, 28–48.

Jo

Lehrmann, D. J., Chaikin, D. H., Enos, P., Minzoni, M., Payne, J. L., Yu, M. Y., Goers, A., Wood, T., Richter, P., Kelley, B. M., Li, X. W., Qin, Y. J., Liu, L. Y., Lu, G., 2015a. Patterns of basin fill in Triassic turbidites of the Nanpanjiang basin: implications for regional tectonics and impacts on carbonate‐platform evolution. Basin Research 27(5), 587–612.

Lehrmann, D. J., Stepchinski, L., Altiner, D., Orchard, M. J., Montgomery, P., Enos, P., Ellwood, B. B., Bowring, S. A., Ramezani, J., Wang, H. M., Wei, J. Y., Yu, M. Y., Griffiths, J. D., Minzoni, M., Schaal, E. K., Li, X. W., Meyer, K. M., Payne, J. L., 2015b. An integrated biostratigraphy (conodonts and foraminifers) and chronostratigraphy (paleomagnetic reversals, magnetic susceptibility, elemental chemistry, carbon isotopes and geochronology) for the Permian–Upper Triassic

ro of

strata of Guandao section, Nanpanjiang Basin, south China. Journal of Asian Earth Sciences 108, 117–135.

Leu, M., Bucher, H., Goudemand, N., 2018. Clade-dependent size response of

re

extinction. Earth-Science Reviews In Press.

-p

conodonts to environmental changes during the late Smithian

Lai, X. L., Wignall, P., Zhang, K., 2001. Palaeoecology of the conodonts Hindeodus

lP

and Clarkina during the Permian–Triassic transitional period. Palaeogeography,

na

Palaeoclimatology, Palaeoecology 171(1–2), 63–72. Li, F., Yan, J. X., Chen, Z. Q., Ogg, J. G., Tian, L., Korngreen, D., Liu, K., Ma, Z. L.,

ur

Woods, A. D., 2015. Global oolite deposits across the Permian–Triassic boundary: a synthesis and implications for palaeoceanography immediately after

Jo

the end-Permian biocrisis. Earth-Science Reviews 149, 163–180.

Liang, D., Tong, J. N., Zhao, L. S., 2011. Lower Triassic Smithian-Spathian Boundary at West Pingdingshan Section in Chaohu, Anhui Province. Science China Earth Sciences 54(3), 372–379. Liang, L., 2017. Early Triassic conodont biostratigraphy in Nanpanjiang Region and

spathio-temporal evolution in South China. Published PhD-thesis. China University of Geosciences (Wuhan), pp. 152. Liang, L., Tong, J. N., Song, H. J., Song, T., Tian, L., Song, H. Y., Qiu, H. O., 2016. Lower-Middle Triassic conodont biostratigraphy of the Mingtang section, Nanpanjiang Basin, South China. Palaeogeography, Palaeoclimatology, Palaeoecology 459, 381–393.

ro of

Liu, J. B., Ezaki, Y., Yang, S. R., Wang, H. F., Adachi, N., 2007.Age and

sedimentology of microbialites after the end-Permian mass extinction in Luodian, Guizhou Province. Journal of Palaeogeography 9, 473–486 (in Chinese with

-p

English abstract)

re

Lyu, Z. Y., Orchard, M. J., Chen, Z. Q., Wang, X. D., Zhao, L. S., Han, C., 2017. Uppermost Permian to Lower Triassic conodont successions from the Enshi area,

lP

western Hubei Province, South China. Palaeogeography, Palaeoclimatology,

na

Palaeoecology 519, 49–64.

Lyu, Z. Y., Zhang, L., Algeo, T. J., Zhao, L. S., Chen, Z. Q., Li, C., Ma, B., Ye, F. H.,

ur

2019. Global-ocean circulation changes during the Smithian–Spathian transition inferred from carbon-sulfur cycle records. Earth-Science Reviews, In press.

Jo

Maekawa, T., Komatsu, T., Koike, T., 2018. Early Triassic Conodonts from the Tahogawa Member of the Taho Formation, Ehime Prefecture, Southwest Japan. Paleontological Research 22(s1), 1–63. Metcalfe, I. 2017. Tectonic evolution of Sundaland. Bulletin of the Geological Society of Malaysia 63, 27–60.

Metcalfe, I., Nicoll, R. S., Willink, R., Ladjavadi, M., Grice, K., 2013. Early Triassic (Induan-Olenekian) conodont biostratigraphy, global anoxia, carbon isotope excursions and environmental perturbations: New data from Western Australian Gondwana. Gondwana Research 23(3), 1136–1150. Meyer, K. M., Yu, M., Lehrmann, D., Van de Schootbrugge, B., Payne, J. L., 2013. Constraints on Early Triassic carbon cycle dynamics from paired organic and

ro of

inorganic carbon isotope records. Earth and Planetary Science Letters 361, 429– 435.

Monnet, C., Klug, C., Goudemand, N., De Baets, K., Bucher, H., 2011. Quantitative

-p

biochronology of Devonian ammonoids from Morocco and proposals for a

re

refined unitary association method. Lethaia 44(4), 469–489.

Muttoni, G., Gaetani, M., Kent, D. V., Sciunnach, D., Angiolini, L., Berra, F., Garzanti,

lP

E., Mattei, M., Zanchi, A., 2009. Opening of the Neo-Tethys Ocean and the

48.

na

Pangea B to Pangea A transformation during the Permian. GeoArabia 14(4), 17–

ur

Orchard, M. J., 2007. Conodont diversity and evolution through the latest Permian and Early Triassic upheavals. Palaeogeography, Palaeoclimatology,

Jo

Palaeoecology 252(1–2), 93–117.

Orchard, M. J., Krystyn, L., 2007. Conodonts from the Induan-Olenekian boundary interval at Mud, Spiti. Albertiana 35, 30–34. Orchard, M. J., Zonneveld, J. P., 2009. The Lower Triassic Sulphur Mountain Formation in the Wapiti Lake area: lithostratigraphy, conodont biostratigraphy,

and a new biozonation for the lower Olenekian (Smithian) Earth Science Sector (ESS) Contribution 20080714. Canadian Journal of Earth Sciences 46(10), 757– 790. Payne, J. L., Bush, A. M., Heim, N. A., Knope, M. L., McCauley, D. J., 2016. Ecological selectivity of the emerging mass extinction in the oceans. Science 353(6305), 1284–1286.

ro of

Payne, J. L., Lehrmann, D. J., Wei, J., Orchard, M. J., Schrag, D. P., Knoll, A. H., 2004. Large perturbations of the carbon cycle during recovery from the end-Permian extinction. Science 305(5683), 506–509.

-p

Qiu, X. C., Tian, L., Wu, K., Benton, M. J., Sun, D. Y., Yang, H., Tong, J. N., 2019.

re

Diverse earliest Triassic ostracod fauna of the non‐microbialite‐bearing shallow marine carbonates of the Yangou section, South China. Lethaia, In press.

lP

Shen, S. Z., Bowring, S. A., 2014. The end-Permian mass extinction: a still

na

unexplained catastrophe. National Science Review 1(4), 492–495. Shen, S. Z., Ramezani, J., Chen, J., Cao, C. Q., Erwin, D. H., Zhang, H., Xiang, L.,

ur

Schoepfer, S. D., Henderson, C. M., Zheng, Q. F., Bowring, S. A., Wang, Y., Li, X. H., Wang, X. D., Yuan, D. X., Zhang, Y. C., Mu, L., Wang, J., Wu, Y. S.,

Jo

2018. A sudden end-Permian mass extinction in South China. Geological Society of America Bulletin 131(1–2), 205–223.

Shen, S. Z., Crowley, J. L., Wang, Y., Bowring, S. A., Erwin, D. H., Sadler, P. M., Cao, C. Q., Rothman, D. H., Henderson, C. M., Ramezani, J., Zhang, H., Shen, Y. A., Wang, X. D., Wang, W., Mu, L., Li, W. Z., Tang, Y. G., Liu, X. L., Liu, L. J.,

Zeng, Y., Jiang, Y. F., Jin, Y. G., 2011. Calibrating the end-Permian mass extinction. Science 334(6061), 1367-1372. Song, H. J., Wignall, P. B., Chen, Z. Q., Tong, J. N., Bond, D. P., Lai, X. L., Zhao, X. M., Jiang, H. S., Yan, C. B., Niu, Z. J., Chen, J., Yang, H., Wang, Y. B., 2011. Recovery tempo and pattern of marine ecosystems after the end-Permian mass extinction. Geology 39(8), 739–742.

ro of

Song, H. J., Wignall, P. B., Chu, D. L., Tong, J. N., Sun, Y. D., Song, H. Y., He, W. H., Tian, L., 2014. Anoxia/high temperature double whammy during the

Permian-Triassic marine crisis and its aftermath. Scientific Reports 4, 4132.

-p

Song, H. J., Wignall, P. B., Dunhill, A. M., 2018. Decoupled taxonomic and

advances 4(10), eaat5091.

re

ecological recoveries from the Permo-Triassic extinction. Science

lP

Song, H. J., Wignall, P. B., Tong, J. N., Yin, H. F., 2013. Two pulses of extinction

na

during the Permian–Triassic crisis. Nature Geoscience 6(1), 52-56. Song, H. Y., Du, Y., Algeo, T. J., Tong, J. N., Owens, J. D., Song, H. J., Tian, L., Qiu,

ur

H. O., Zhu, Y. Y., Lyons, T. W., 2019. Cooling-driven oceanic anoxia across the Smithian/Spathian boundary (mid-Early Triassic). Earth-Science Reviews, In

Jo

press.

Song, H. Y., Tong, J. N., Algeo, T. J., Horacek, M., Qiu, H. O., Song, H. J., Tian, L., Chen, Z. Q., 2013. Large vertical δ13CDIC gradients in Early Triassic seas of the South China craton: Implications for oceanographic changes related to Siberian Traps volcanism. Global and Planetary Change 105, 7–20.

Sweet, W. C., 1970. Uppermost Permian and Lower Triassic Conodonts of the Salt Range and Trans-Indus Ranges, West Pakistan. In: Kummel, B., Teichert, C., eds., Stratigraphic Boundary Problems: Permian and Triassic of West Pakistan. University of Kansas, Department of Geology Special Publications, Kansas, 4, 207–275 Stanley, S. M., 2009. Evidence from ammonoids and conodonts for multiple Early

ro of

Triassic mass extinctions. Proceedings of the National Academy of Sciences 106(36), 15264–15267.

Sun, D. Y., Tong, J. N., Xiong, Y. L., Tian, L., Yin, H. F., 2012. Conodont

-p

biostratigraphy and evolution across Permian-Triassic boundary at Yangou

re

Section, Leping, Jiangxi Province, South China. Journal of Earth Science 23(3), 311–325.

lP

Sun, Y. D., Joachimski, M. M., Wignall, P. B., Yan, C. B., Chen, Y. L., Jiang, H. S.,

na

Wang, L. N., Lai, X. L., 2012. Lethally hot temperatures during the Early Triassic greenhouse. Science 338(6105), 366–370.

ur

Sun, Y. D., Wignall, P. B., Joachimski, M. M., Bond, D. P. G., Grasby, S. E., Sun, S., Yan, C. B., Wang, L. N., Chen, Y. L., Lai, X. L., 2015. High amplitude redox

Jo

changes in the late Early Triassic of South China and the Smithian–Spathian extinction. Palaeogeography, Palaeoclimatology, Palaeoecology, 427, 62-78.

Tian, L., Tong, J. N., Algeo, T. J., Song, H. J., Song, H. Y., Chu, D. L., Shi, L., Bottjer, D. J., 2014. Reconstruction of Early Triassic ocean redox conditions based on framboidal pyrite from the Nanpanjiang Basin, South China. Palaeogeography,

Palaeoclimatology, Palaeoecology 412, 68-79. Tian, L., Tong, J. N., Xiao, Y. F., Benton, M. J., Song, H. Y., Song, H. J., Liang, L., Wu, K., Chu, D. L., Algeo, T. J., 2019. Environmental instability prior to end-Permian mass extinction reflected in biotic and facies changes on shallow carbonate platforms of the Nanpanjiang Basin (South China). Palaeogeography, Palaeoclimatology, Palaeoecology 519, 23–36.

ro of

Tong, J. N., Yin, H. F., 2002. The Lower Triassic of South China. Journal of Asian Earth Sciences 20(7), 803–815.

Tong, J. N., Zakharov, Y. D., Orchard, M. J., Yin, H. F., Hansen, H. J., 2004. Proposal

-p

of Chaohu section as the GSSP candidate of the Induan-Olenekian

re

boundary. Albertiana 29, 13–27.

Tong, J. N., Zuo, J. X., Chen, Z. Q., 2007. Early Triassic carbon isotope excursions

lP

from South China: proxies for devastation and restoration of marine ecosystems

389.

na

following the end‐Permian mass extinction. Geological Journal 42(3–4), 371–

ur

Wang, C. Y., 1995. Conodonts from Permian-Triassic boundary beds and biostratigraphical boundary at the Zhongxindadui Section at Meishan,

Jo

Changxing, Zhejiang Province. Chinese Science Bulletin 40, 719–722.

Wang, G. Q., Xia, W. C., 2004. Conodont zonation across the Permian-Triassic boundary at the Xiakou section, Yichang City, Hubei Province and its correlation with the Global Stratotype Section and Point of the PTB. Canadian Journal of Earth Sciences 41(3), 323–330.

Wang, L. N., Wignall, P. B., Wang, Y. B., Jiang, H. S., Sun, Y. D., Li, G. S., Yuan, J. L., Lai, X. L., 2016. Depositional conditions and revised age of the Permo-Triassic microbialites at Gaohua section, Cili County (Hunan Province, South China). Palaeogeography, Palaeoclimatology, Palaeoecology 443, 156–166. Wei, H. Y., Shen, J., Schoepfer, S. D., Krystyn, L., Richoz, S., Algeo, T. J., 2015. Environmental controls on marine ecosystem recovery following mass

ro of

extinctions, with an example from the Early Triassic. Earth-Science Reviews 149, 108–135.

Wu, K., Tian, L., Liang, L., Metcalfe, I., Chu, D., Tong, J. N., 2019. Recurrent biotic

-p

rebounds during the Early Triassic: biostratigraphy and temporal size variation of

re

conodonts from the Nanpanjiang Basin, South China. Journal of the Geological Society, In press.

lP

Xiao, Y. F., Suzuki, N., He, W. H., 2018a. Low-latitudinal standard Permian

na

radiolarian biostratigraphy for multiple purposes with Unitary Association, Graphic Correlation, and Bayesian inference methods. Earth-Science

ur

Reviews 179, 168–206.

Xiao, Y. F., Wu, K., Tian, L., Benton, M. J., Du, Y., Yang, H., Tong, J. N., 2018b.

Jo

Framboidal pyrite evidence for persistent low oxygen levels in shallow-marine facies of the Nanpanjiang Basin during the Permian-Triassic transition. Palaeogeography, Palaeoclimatology, Palaeoecology 511, 243–255.

Xie, S. C., Pancost, R. D., Wang, Y. B., Yang, H., Wignall, P. B., Luo, G. M., Jia, C. L., Chen, L., 2010. Cyanobacterial blooms tied to volcanism during the 5 my

Permo-Triassic biotic crisis. Geology 38(5), 447–450. Yan, C. B., Wang, L. N., Jiang, H. S., Wignall, P. B., Sun, Y. D., Chen, Y. L., Lai, X. L., 2013. Uppermost Permian to Lower Triassic conodonts at Bianyang section, Guihzou province, South China. Palaios 28(8), 509–522. Yang, B., Lai, X. L., Wignall, P. B., Jiang, H. S., Yan, C. B., Sun, Y. D., 2012. A newly discovered earliest Triassic chert at Gaimao section, Guizhou, southwestern

ro of

China. Palaeogeography, Palaeoclimatology, Palaeoecology 344, 69–77.

Yin, H. F., Jiang, H. S., Xia, W. C., Feng, Q. L., Zhang, N., Shen, J., 2014. The end-Permian regression in South China and its implication on mass

-p

extinction. Earth-Science Reviews 137, 19–33.

re

Yin, H. F., Xie, S. C., Luo, G. M., Algeo, T. J., Zhang, K. X., 2012. Two episodes of environmental change at the Permian-Triassic boundary of the GSSP section

lP

Meishan. Earth-Science Reviews 115(3), 163–172.

na

Yin, H. F., Zhang, K. X., Tong, J. N., Yang, Z. Y., Wu, S. B., 2001. The Global Stratotype Section and Point (GSSP) of the Permian-Triassic

ur

boundary. Episodes 24(2), 102–114. Yuan, D. X., Chen, J., Zhang, Y. C., Zheng, Q. F., Shen, S. Z., 2015. Changhsingian

Jo

conodont succession and the end-Permian mass extinction event at the Daijiagou section in Chongqing, Southwest China. Journal of Asian Earth Sciences 105, 234–251.

Yuan, D. X., Shen, S. Z., 2011. Conodont succession across the Permian-Triassic Boundary of the Liangfengya Section, Chongqing, South China. Acta

Paleontologica Sinica 50, 420–438 (in Chinese). Yuan, D. X., Shen, S. Z., Henderson, C. M., Chen, J., Zhang, H., Feng, H. Z., 2014. Revised conodont-based integrated high-resolution timescale for the Changhsingian Stage and end-Permian extinction interval at the Meishan sections, South China. Lithos 204, 220–245. Yuan, D. X., Shen, S. Z., Henderson, C. M., Chen, J., Zhang, H., Zheng, Q. F., Wu, H.

ro of

C., 2018. Integrative timescale for the Lopingian (Late Permian): A review and update from Shangsi, South China. Earth-Science Reviews 188, 190–209.

Zhang, K. X., 1987. The Permo-Triassic conodont fauna in Changxing area, Zhejiang

re

University of Geosciences 12, 193–200.

-p

Province and its stratigraphic significance. Earth Science–Journal of China

Zhang, K. X. , Lai, X. L., Ding, M. H. , Liu, J. H. , 1995. A conodont sequence and its

lP

global correlation to the Permian–Triassic boundary in the Meishan section,

na

Changxing, Zhejiang, China. Earth Science–Journal of China University of Geosciences 20, 669–676.

ur

Zhang, K. X., Lai, X. L., Tong, J. N., Jiang, H. S., 2009. Progresses on study of conodont sequence for the GSSP section at Meishan, Changxing, Zhejiang

Jo

province, South China. Acta Palaeontologica Sinica 48, 474–486.

Zhang, K. X., Tong, J. N., Shi, G. R., Lai, X. L., Yu, J. X., He, W. H., Peng, Y. Q., Jin, Y. L., 2007. Early Triassic conodont-palynological biostratigraphy of the Meishan D Section in Changxing, Zhejiang Province, South China. Palaeogeography, Palaeoclimatology, Palaeoecology 252(1–2), 4–23

Zhang, L., Orchard, M. J., Brayard, A., Algeo, T. J., Zhao, L. S., Chen, Z. Q., Lyu, Z. Y. 2019. The Smithian/Spathian boundary (late Early Triassic): a review of ammonoid, conodont, and carbon-isotopic criteria. Earth-Science Reviews, In press. Zhang, Y., Zhang, K. X., Shi, G. R., He, W. H., Yuan, D. X., Yue, M. L., Yang, T. L., 2014. Restudy of conodont biostratigraphy of the Permian–Triassic boundary

ro of

section in Zhongzhai, southwestern Guizhou Province, South China. Journal of Asian Earth Sciences 80, 75–83.

Zhao, J. K., Sheng, J. Z., Yao, Z. Q., Liang, X. L., Chen, C. Z., Rui, L., Liao, Z.T.,

-p

1981. The Changhsingian and the Permian–Triassic boundary in South China.

re

Bulletin of the Nanjing Institute of Geology and Palaeontology 2, 1–112. Zhao, L. S., Chen, Y. L., Chen, Z. Q., Cao, L., 2013. Uppermost Permian to Lower

lP

Triassic conodont zonation from Three Gorges area, South China. Palaios 28(8),

na

523–540.

Zhao, L. S., Orchard, M. J., Tong, J. N., Sun, Z. M., Zuo, J. X., Zhang, S. X., Yun, A.

ur

L., 2007. Lower Triassic conodont sequence in Chaohu, Anhui Province, China and its global correlation. Palaeogeography, Palaeoclimatology,

Jo

Palaeoecology 252(1–2), 24–38.

Zhao, L. S., Tong, J. N., Sun, Z. Y., Orchard, M. J., 2008. A detailed Lower Triassic conodont biostratigraphy and its implications for the GSSP candidate of the Induan–Olenekian boundary in Chaohu, Anhui Province. Progress in Natural Science 18(1), 79–90.

Zuo, J. X., Tong, J. N., Qiu, H. O., Zhao, L. S., 2006. Carbon isotope composition of the Lower Triassic marine carbonates, Lower Yangtze region, South

Jo

ur

na

lP

re

-p

ro of

China. Science in China Series D 49(3), 225–241.

Table 1 GPS coordinates of the sections in this study Latitude(N )

Longtitude(E )

Sections

Latitude(N )

Shangsi

31°26′31″

104°09′32″

Gaimao

26°26′14″ 106°44′43″

Chaotian

32°38′58″

105°53′19″

Jiarong

25°55′20″ 106°34′01″

Daxiakou

31°06′02″

110°48′50″

Zhongzhai

26°09′25″ 105°17′11″

Jianshi

30°31′58″

109°39′50″

Bianyang

25°37′51″ 106°37′51″

Ganxi

30°07′27″

109°26′56″

Guandao

25°37′40″ 106°37′56″

Pingdingshan

31°38′01″ 117°49′50″

Sidazhai

Meishan

31°04′36″ 119°41′50″

Ganheqiao

Huangzhisha n

30°55′19″ 119°59′21″

Dawen

25°35′08″ 106°39′02″

Yangou

29°10′03″ 117°20′59″

Dajiang

25°35′37″ 106°38′51″

Gaohua

29°22′37″ 110°54′50″

Jianzishan Dajiagou

Jo

Mingtang

re

-p

25°14′05″ 106°06′41″

30°09′58″ 109°00′27″

Dala

23°21′52″ 105°47′15″

29°54′20″ 106°30′49″

Motianling

23°24′34″ 107°00′18″

29°30′00″ 106°25′10″

Wuzhuan

24°21′45″ 107°20′02″

26°19′29″ 106°41′40″

Taiping

23°25′01″ 107°26′38″

lP

23°24′08″ 106°00′12″

ur

Qingyan

25°35′52″ 106°09′48″

Pojue

na

Liangfengya

Longtitude(E )

ro of

Sections

25°36′05″ 106°38′47″

Table 2 Taxonomical revisions used in the present study. section (Authors)

figure

Original

Bed(Sample)

Our

determination

number

determination

Reasons First established by Nicoll et al. (2002), H. eurypyge is carminiscaphate with a tall anterior and 3-10 laterally compressed carina denticles, and those denticles are of sub-uniform size and closely appressed with triangular tips in

Jianzishan (Bai et al.,

pl.1. 6

H.eurypyge

JZS-2+0.5

H.sp.

are truncated and chisel like in

ro of

2017)

juvenlie elments. The posteriors tips mature spceciemens and basal vavity deeply excavated with narrow grove extnding anteriorly under the cusp.

But in Bai et al.(2017), we can't see

Jianshi (Lyu et al.,

Fig.5. 5

H. parvus

JS4T136-2

H. praeparvus

Jianshi (Lyu et al.,

Fig.5.

H. sp.

13

The denticles of this specimen declines in height toward the posterior end, and the last three dentilces are slightly lager than the previous, which make this specimens H. postparvus has small, erected anterior denticles and stongly divergent posterior denticles. The cusp is only sligtly bigger than other

JST16

H. postparvus

denticles. In Lyu et al. (2017), this speciemens has divergent posterior denticles and the cusp is also only slightly lager than the adjacent denticle.

Jo 2016)

denticles are almost triangularis .

Ns. dieneri is a subtriangular segminate element with 3 to 9 erect or gradually reclined posteriorly

Mingtang (Liang et al.,

margin of this specimen, and the 6

more like a H. pareparvus.

ur

2017)

na

lP

2017)

re

-p

the widened and rounded posterior

Fig.4. 5

Ns. dieneri M. 3

denticels. The denticles also MT-18+1.2

Ns. clinatus

progressively increase in size towrd cusp. In Liang et al. (2016), this speciemen has straight basal line, and the lower part of the denticles are broaden.

Qingyan (Ji et al., 2011

Fig.4. 6

Ns. spathi

43

Sp. spathi

An unification of genus name

) According to Clark (1959), Pg. geiseri is a palm-like element with large and straight basal part. 9-13 Bianyang (Yan et al., 2013)

needle-like and nearly the same

Fig.7.

Pg.geiseri

FF

52

Pg.peculiaris

size's denticles develop on the upper part. In Yan et al. (2013) the speciemns has backward-declined and dispersed denticles,, which is more like a Pg. peculiaris.

Daijiagou (Yuan et al., 2015)

ro of

These specimens have a very wide, asymmetrical, lobed, swollen and

pl. 6. 25,

H. sp.

26, 28

DJG-1.05-1.10

I. inflata

thickend cup which have no nodes

on the both side. According to these, we revised it into I. inflata .

Huangzhishan pl.6. 9

H. latidentatus

lP

2008)

Huangzhishan

H. latidentatus

C7-1

Jo

Chaotian (Ji et al., 2007)

pl.2.

22-23

praeparvus with medium sized cusp and 4-8 denticles. But the latter has

closer denticles while the former has wider and wider gaps between the denticles towards the posterior. In this specimen, the cusp is broken and the gaps between the denticles do not show wider toward the posterior. This specimen has medium-sized

H. typicalis

cusp and the denticles exhibited a "S" like outline, which are the typical features of H. typicalis. C. zhejiangensis is characterized by ans elongate-oval-shaped platform.

ur

2008)

pl. 6. 8

H. sp.

na

(Chen et al.,

C18-3

re

(Chen et al.,

-p

H.latidentatus is similar with H.

The most widest point locates at the middle, with subparallel lateral C.orchardi

D10

C. zhejiangensis

margins. The posterior end of this sepecies is squarely rounded. Its carina is low and composed of largely discret denticles, with a samll and erect cusp at its poeterior which is often surrounded by a relatvely narrow brim.

Zhongzhai (Metcalfe and Nicoll, 2007)

pl.1. 9

C. tulongensis

30

C. sp.

A mostly broken specimens which should classified into C. sp..

This specimen has two large

Dala (Chen et al.,

Pl.4. 1

H. parvus

DAL-15

2018)

H.

denticles with similar size in the

bicuspidatus

anterior part, which is a special feature of H. bicusidatus.

Dala (Chen et al.,

Pl.4. 2

H. peculiaris

DAL-15

2018)

H. bicuspidatus

There is another nearly same-sized denticle with the cusp, which make this specimen into H. bicuptidatus. H. anterodentatus is

Dala (Chen et al.,

Pl.4. 3

H. peculiaris

DAL-15

2018)

H. anterodentatus

characterized by several much smaller denticles than the cusp, and they are located at the interior part of the cusp.

ro of

H. anterodentatus is characterized by several quite small

Dala (Chen et al.,

Pl.4. 4

H. parvus

DAL-15

2018)

H.

denticles which are located at the

anterodentatus

interior part of the cusp. This

speciemen has three small denticles

(Zhang et al.,

19

Ns. cristagalli

107

Ns. dieneri

(Jiang et al., 2007)

cristagalli has 5-13 dendicles, the ratio of width:height:length is 1:3:4, the highest point locates slightly posterior unit midlength, the cusp is short and thick. The basal margin consipicuously upward beneath the specimens in Zhang et al. (2007) has 1:1 in the ratio of length:width, and the cusp is rather long, which make it more like a Ns. dieneri. Jiang et al. (2011) established this species by the materials from The

ur Jo Meishan

According to Sweet (1970), Ns.

posterior third of the unit. The

na

2007)

Fig.3.

lP

Meishan

re

-p

in the front of cusp.

Shangsi section. This species is characterized by an symmetrical swollen or thickened cusp. One prominent lateral node or denticle is

pl.5. 8, 9, 11-13

I. staeschei

27d

I. huckriedei

located on the cup, while smaller additional nodes may be developed. The prominent node is inclined and curved posteriorly. The differences between I. huckriedei and I. staeschei include: the former has closely spaced denticles and more than twice large cusp than that of the

adjacent denticles; the lateral node on the cup in I. huckriedei is inclined and curved posteriosly.

A prominent lateral node on the cup

Shangsi (Jiang et al.,

pl.3. 1

I. lobata

30b

I. huckriedei

2011)

A deticle with similar size as the H. anterodentatus

31a, 33

H.

cusp can be seen in these two

bicuspidatus

specimens, so we reassign them into

ro of

pl.1. 3, 5

2011)

H. bicuspidatus.

Guandao (Lhermann et

E. costatus is characterized by

Fig.5. 7

Eu. sp.

WG-88

Eu. costatus

transverse ridge-like denticles on a platform-like base.

ur

na

lP

re

-p

al., 2015)

Jo

node is inclined and curved postersoisly

Shangsi (Jiang et al.,

is present in this spiecimen, and the

Table 3 Identification of the conodont species in the initial matrix.

11 12 13 14 15 16 17 18 19 20

C. zhangi C. zhejiangensis Nc. discreta Ch. gondolelloides

31 32 33 34 35 36 37 38 39

H. pisai H. postparvus H. praeparvus

40 41 42

H. priscus

Jo

ur

na

21

C. postwangi C. subcarinata C. taylorae C. tulongensis C. wangi C. yini

24 25 26 27 28 29 30

Cn. conservativa Cr. breviramulis Cr. kochi D. discreta Eu. costatus Eu. hamadai Gu. bransoni Gu. robustus H. anterodentatus H. bicuspidatus H. changxingensis H. eurypyge H.inflatus H. latidentatus H. parvus H. peculiaris

43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59

H. socioensis H. typicalis I. huckriedei I. inflata I. isarcica I. lobata I. peculiaris I. staeschei I. turgida

60 61 62 63

64 65 66 67 68 69 70 71 72 73

Ns. dieneri Ns. novaehollandiae Ns. pakistanensis Ns. peculiaris Ns. sp.v Ns. tongi Ns. triagularis Nv. abruptus Nv. ex gr. waageni Nv. pingdingshanensis Nv. posterolongatus

ro of

10

23

Ch. timorensis

Ic. collisoni Ic. crassatus

Ic. zaksi M. ultima Ng. n. sp. A Ni. kockeli Ni. germanica Ns. brochus Ns. chaohuensis Ns. chii Ns. cristagalli

-p

3 4 5 6 7 8 9

22

re

2

C. carinata C. changxingensis C. deflecta C. kazi C. krystyni C. lehrmanni C. meishanensis C. nassichuki C. orchardi C. parasubcarinata C. planata

lP

1

Ns. curtatus

74 75 76 77 78 79 80 81 82 83

Nv. spitiensis Pc. obliqua Pg. peculiaris Sp. spathi Sw. kummeli Tr. brevissilmus Tr. homeri Tr. symetricus Tr. sosioensis

Table 4 Identification of conodont species in the final matrix.

10 11 12 13 14

C. planata C. subcarinata C. taylorae C. wangi C. yini C. zhangi

15

27 28 29 30 31 32

H. bicuspidatus H. changxingensis H. eurypyge H. inlfatus H. latidentatus H. parvus H. pisai

33

H. postparvus 34 H. praeparvus 35

H. priscus 36 H. sosioensis

Jo

ur

na

lP

C. zhejiangensis 16 Nc. discreta Ch. 17 gondolelloides 18 Ch. timorensis

26

Cr. kochi D. discreta Eu. costatus Eu. hamadai Gu. bransoni Gu. robustus H. anterodentatus

37 38 39 40 41 42 43 44 45 46 47 48 49 50

H. typicalis I. huckriedei I. inflata I. isarcica I. lobata I. peculiaris I. staeschei I. turgida Ic. collisoni Ic. crassatus Ic. zaksi Ni. kockeli Ni. germanica Ns. brochus Ns. chaohuensis Ns. chii

51 52 53

55 56 57 58 59 60 61 62 63

Ns. dieneri Ns. novaehollandiae Ns. pakistanensis Ns. sp.v Ns. tongi Ns. triagularis Nv. abruptus Nv. ex gr. waageni Nv. pingdingshanensis Nv. spitiensis Pc. obliqua Pg. peculiaris Sp. spathi Sw. kummeli

ro of

9

19 20 21 22 23 24 25

-p

8

C. carinata C. changxingensis C. deflecta C. krystyni C. lehrmanni C. meishanensis C. orchardi C. parasubcarinata

re

1 2 3 4 5 6 7

Ns. cristagalli 54 Ns. curtatus

64 65 66 67 68 69

Tr. brevissilmus 70 Tr. homeri 71

Tr. symetricus 72 Tr. sosioensis