Restoration of reef ecosystems following the Guadalupian–Lopingian boundary mass extinction: Evidence from the Laibin area, South China

Accepted Manuscript Restoration of reef ecosystems following the Guadalupian–Lopingian boundary mass extinction: Evidence from the Laibin area, South China

Yuangeng Huang, Zhong-Qiang Chen, Laishi Zhao, George D. Stanley, Yu Pei, Wanrong Yang, Junhua Huang PII: DOI: Reference:

S0031-0182(17)30509-6 doi: 10.1016/j.palaeo.2017.08.027 PALAEO 8420

To appear in:

Palaeogeography, Palaeoclimatology, Palaeoecology

Received date: Revised date: Accepted date:

13 May 2017 5 July 2017 ###ACCEPTEDDATE###

Please cite this article as: Yuangeng Huang, Zhong-Qiang Chen, Laishi Zhao, George D. Stanley, Yu Pei, Wanrong Yang, Junhua Huang , Restoration of reef ecosystems following the Guadalupian–Lopingian boundary mass extinction: Evidence from the Laibin area, South China, Palaeogeography, Palaeoclimatology, Palaeoecology (2017), doi: 10.1016/ j.palaeo.2017.08.027

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ACCEPTED MANUSCRIPT Restoration of reef ecosystems following the Guadalupian‒Lopingianboundary mass extinction: Evidence from the Laibin area, South China

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Yuangeng Huanga, Zhong-Qiang Chena, *, Laishi Zhaob, George D. Stanley Jr.c, Yu

State Key Laboratory of Biogeology and Environmental Geology and School of

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a

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Peia, Wanrong Yang d, Junhua Huangb

Earth Science, China University of Geosciences (Wuhan), Wuhan 430074, China State Key Laboratory of Geological Process and Mineral Resources,

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Department of Geosciences, University of Montana, Missoula, MT 59812, USA

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Nanjing Institute of Geology and Paleontology, Chinese Academy of Sciences,

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Nanjing 21008, China

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ChinaUniversity of Geosciences (Wuhan), Wuhan 430074, China

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* Corresponding author.

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E-mail address: [email protected] (Z.-Q., Chen).

Abstract

The Guadalupian‒Lopingian boundary (GLB), also Middle‒Late Permian boundary, mass extinction severely destroyed metazoan reef ecosystems, although some studies argued that both biotic and environmental turnover across the GLB are not so obvious. When compared with prolifically developed reefs in the Capitanian,

ACCEPTED MANUSCRIPT the Wuchiapingian reef examples appear depauperate and almost 89% of the carbonate production in these bioconstructions was lost. Here, we report a typical sponge reef from the Wuchiapingian stage in the Tieqiao section, central Guangxi Province, South China. The Tieqiao reef might represent the only example of a

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Wuchiapingian metazoan reef in the eastern Palaeo-Tethys region. It provides insight

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into ecosystem restoration following the GLB extinction. Major constructors of the

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Tieqiao reef are sponges (Peronidella, Parauvanella, Sollasia, Tabulozoa, and Amblysiphonella), algae (Anthracoporella, Archaeolithporella, Permocalculus,

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Gymnocodium) and Tubiphytes. This reef is well constrained as middle‒late

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Wuchiapingian in age by the Clarkina orientalis conodont zone. Carbonate carbon isotope excursions experienced negative spikes near the GLB and multiple

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perturbations in the early‒middle Wuchiapingian, and remained relatively stable

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during re-establishment of metazoan reefs in middle‒late Wuchiapingian. Conodont oxygen isotopes showed that the sea surface temperature (SST) was extremely

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high, >30 ℃ during late Capitanian time, punctuated by a short cooling event and

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global regression associated with the GLB extinction, and followed by high SST and rapid rise in sea level in the early Wuchiapingian. The reemergence of the Tieqiao reef coincided with the initial cooling in surface oceans and sea-level fall during the middle‒late Wuchiapingian. Accordingly, reef ecosystems experienced a long-term depletion worldwide in early‒middle Wuchiapingian time and then recovered ~2.5 Myr after the GLB extinction based on estimate in integration of both conodont biostratigraphy and radiometric ages.

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Keywords: Middle Permian; Late Permian; Wuchiapingian; Reef ecologic crisis;

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Reef-building organisms; Recovery

ACCEPTED MANUSCRIPT 1. Introduction

Study of the fossil record of major benthos including foraminifers, corals, brachiopods and ammonoids from South China, demonstrates distinct evidence of an

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extinction across the Guadalupian‒Lopingian (Middle‒Late Permian) boundary (GLB)

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(Jin et al. 1994a; Stanley and Yang 1994; Shen and Shi, 1996, 2002; Shi et al. 1999;

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Yang et al. 2000; Wang and Sugiyama 2000; Kaiho et al., 2005; Wignall et al., 2009a). The magnitude and extent of this biocrisis however, had been recently called into

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question because no major biotic and environmental turnover has ever been

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demonstrated in the key outcrops (Clapham et al., 2009; but see Zhang et al., 2015). Instead, one biotic extinction may be calibrated to the mid-Capitanian (Wignall et al.,

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2009b; Bond et al., 2010). However, a major ecologic crisis can be documented very

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well by metazoan reef turnover across the GLB. The GLB transition witnesses the demise of many important Guadalupian reef domains, such as the famous Capitan reef

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complex (Newell, 2001) as well as examples in Indochina and the southwest

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Palaeo-Tethys region (Weidlich, 2002a, b). The number of the reefs dramatically declined during these times with ~100 Guadalupian reef sites evaluated (Weidlich, 2002b). However only a few reefs or buildups are developed in the Wuchiapingian worldwide (Flügel and Kiessling, 2002). The GLB extinction therefore has been considered a second-order reef crisis due to reduction of reef carbonate production calculated to have been around 88.7% with a reduction of normalized reef abundance calculated at 47% (Flügel and Kiessling, 2002). In addition, the GLB biocrisis was

ACCEPTED MANUSCRIPT associated with the greatest drops in global sea-level, which reached the lowest levels during the Phanerozoic history (Ross and Ross, 1987, 1994; Hallam and Wignall, 1997, 1999; Chen et al., 1998, 2009; Haq and Schutter, 2008). The biotic and environmental changes over the GLB transition therefore have attracted increasing

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interest from both palaeontologists and geologists. The combination of both a

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biocrisis and a dramatic loss of shallow marine habitats, attributed to this great

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sea-level fall, may accounted for the collapse of reef ecosystems worldwide (Hallam and Wignall, 1997, 1999; Chen et al., 2009; Qiu et al., 2013).

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Unlike the well-studied biotic extinctions and their aftermaths (i.e., the Early

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Triassic; Chen and Benton, 2012), the post-extinction ecosystem of the GLB crisis has long remained poorly understood due largely to a lack of complete marine sections

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spanning the latest Capitanian into the early Wuchiapingian time (Hallam and Wignall,

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1997). This lack of key stratigraphic sections has meant that establishing precise collapse and rebuilding processes of marine ecosystems during and after the GLB

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mass extinction has been difficult and problematic. Although several studies indicated

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a rapid recovery of benthos (i.e., brachiopods) following the GLB extinction (Chen et al., 2005; Shen et al., 2007), the coeval reef ecosystems appeared depauperate worldwide except that bioconstructions are relatively common in the Zechstein successions (Upper Permian) of the Southern Permian Basin, Central Europe (Germany, Poland, northern UK). These Zechstein bioconstructions however possess primary frame-builders of microbes in association with bryozoans (Peryt et al., 2012), indicating clearly microbial proliferation, which is characteristic of degraded

ACCEPTED MANUSCRIPT ecosystems in the aftermaths of major mass extinctions (i.e., the Early Triassic; Kershaw et al., 2012; Chen et al., 2014). A metazoan reef in South China, in the Wuchiapingian (Yang, 1987) might be the only example known. Although some small, coeval bioherms occur sporadically in South China (Shen and Xu, 2005), the

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Wuchiapingian example appears to be the only example of a fully developed reef. The

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degraded nature of the Wuchiapingian reef ecosystems seems to indicate the effect of

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the GLB mass extinction but its magnitude remains unclear.

In addition, unlike most regions of the world, the Laibin area of central Guangxi

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Province, South China records exceptionally complete marine Middle‒Late Permian

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successions, which are well exposed at two closely situated sections at Tieqiao and Penglaitan (Fig. 1C). Of these two, the Penglaitan section was selected as the Global

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Stratotype and Pont (GSSP) for the G‒L boundary (Jin et al. 2006). The Tieqiao

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section records not only the continuous G‒L boundary beds, but also a distinct metazoan reef during the Wuchiapingian (Fig. 2). The latter therefore provides a

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unique opportunity to evaluate ecosystem recovery following the G‒L mass extinction.

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Although mentioned in several earlier publications (Yang et al., 1987; Sha et al., 1990; Shen et al., 2007; Chen et al., 2009), the Wuchiapingian reef has remained enigmatic in terms of geometry, reefal structures and reef building organisms. Accordingly, the present study aims to document the Wuchiapingian metazoan reef and chart the stratigraphic distribution of reef building organisms in the aftermath of the G‒L extinction, and ultimately seeks to better clarify the nature of the reef ecosystem recovery. Environmental controls on the restoration of this reef ecosystem are

ACCEPTED MANUSCRIPT revealed by our newly obtained carbon isotopes combined with previously published seawater surface temperature derived from conodont oxygen isotopes (Chen et al., 2011, 2013).

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2. Palaeogeographic and stratigraphic settings

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During the GLB transition, South China was located near the equator in the eastern Palaeo-Tethys Ocean (Fig. 1A; Ziegler et al., 1998). The Laibin area is

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situated at the central Guangxi Province, South China and located in the eastern

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Dianqiangui Basin (Fig. 1B) (Feng et al., 1994; Chen et al., 1998; Wang and Jin, 2000). The Laibin area represents the ramp settings between carbonate platforms

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located to the west and north (Heshan area) and the deep-water Qingzhou Trough to

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the southeast (Jin et al., 1994b). The complete Middle‒Late Permian succession including the continuous GLB successions, are well exposed at the Tieqiao and

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Penglaitan sections. These two sections although ~10 km apart both record

1C).

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comparable successions along the western and eastern limbs of a large syncline (Fig.

The Tieqiao section is located ~4 km southeast of Laibin city in the Guangxi Province, South China (Fig. 1C). Therein the Middle‒Late Permian succession is subdivided into the Maokou and Heshan formations in ascending order (Sha et al., 1990). The uppermost Maokou Formation consists of massive pale grey slope debris and mound limestone known as the Laibin Limestone (Jin et al., 2006; Shen et al.,

ACCEPTED MANUSCRIPT 2007; Chen et al., 2009; Fig. 2). This distinctive massive limestone unit hosts the G‒L boundary, and the overlying Heshan Formation is comprised of five units. The first is characterized by siliceous shale and chert; the second unit is dominated by alternation of thin bedded cherty limestone and siliceous mudstone chert; the third unit consists

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of alternations of dark brown, thin-bedded siliceous mudstone and medium-bedded

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limestone, the fourth unit is composed of massive reefal limestone and the fifth unit is

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limestone or limestone with chert nodules (Sha et al., 1990).

The Laibin Limestone yields the Jinogondolella granti conodont zone, and the

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GLB, marked by the first occurrence of the Clarkina postbitteri postbitteri, is placed

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~0.5 m below the top of the Laibin Limestone (Jinet al., 2006; Shen et al., 2007). Succeeding the C. postbitterizone, the C. dukouensis and C. asymmetrica conodont

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zones occur at the basal Heshan Formation in Tieqiao (Mei et al., 1999). The

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remaining lower Heshan Formation is characterized by the presence of the C. leveni and C. liangshensis conodont zones (Mei et al., 1999; Shen et al., 2007), while the

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reefal limestone unit age is constrained as late Wuchiapingian by the C. orientalis

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conodont zone (Mei et al., 1999; Shen et al., 2007).

3. Analytical Methods and Techniques

3.1. Facies analysis

Field data were supplemented by petrographic study of the carbonate microfacies

ACCEPTED MANUSCRIPT and fossil content. Additional specimens, primarily of calcisponges, were also collected to identify the major reef framework builders and dwellers. Point-counting of 5‒10 thin sections of each facies was undertaken to determine percentages of various skeletal components, micrite and grains following the methods described by

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Chen et al. (2015). The average number of allochems per field of view was used to

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calculate the proportion of allochems in each facies/microfacies. Given the sequential

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facies successions within the reef complex, trends of allochems with particular positions within the reef can be easily demonstrated visually (Fig. 5). This made

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interpretation of depositional environments simpler and helped to constrain the

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possible sea-level fluctuations throughout the mound complex. Environmental and bathymetric interpretations of facies follow the Standard Microfacies (SMF) scheme

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of Wilson as modified by Flügel (2004).

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More than 50 oriented samples were collected, slabbed, and thin-sectioned using conventional petrologic techniques. All thin sections were observed under objective

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lens of Leica DM2500P Microscope. A Hitachi-SU8010 scanning electron

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microscope (SEM) equipped with energy dispersive X-ray spectrometry (EDS) was also employed to observe thin sections, and associated secondary minerals in a micron scale. EDS was applied to determine the mineral composition of the microbial carbonates. Fresh hand samples and thin sections were etched with 1% acetic acid for 5 seconds prior to SEM examination and all samples were coated by platinum prior to SEM imaging and EDS analysis.

ACCEPTED MANUSCRIPT 3.2.Carbon isotopic geochemistry

To determine environmental changes in the aftermath of the GLB mass extinction, both carbon (δ13C) and oxygen (δ18O) isotopes of the Heshan Formation were

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measured. A total 101 samples were powdered for whole rock carbon isotopic analysis,

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and fresh samples were collected from the outcrop. Weathered surfaces and large

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veins were trimmed and each sample was cut into small pieces in the laboratory. The rock chips were then ground to fine powder (< 200 mesh) using a stainless-steel puck

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mill that was cleaned between samples by grinding with red quartz sand. Under

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vacuum, the sample powder was reacted offline with 100% H3PO4 for 24h at 25 ℃. The carbon isotope composition of the generated CO2 was measured on a Finnigan

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MAT 251 mass spectrometer. All isotopic data are reported as per mil (‰) relative to

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Vienna Pee Dee belemnite (V-PDB) standard, based on duplicate analyses of national standards GBW04416 (δ13C = +1.61‰, δ18O = –11.59‰) and GBW04417 (δ13C =

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+6.06‰, δ18O = –24.12‰).The analytical precision is better than ±0.1‰ for δ13C and

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±0.2‰ for δ18O based on duplicate analyses. The microscope, MAT 251, and EDS equipped-SEM reside at the State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences (Wuhan).

4. Results

4.1.Reef setting and geometry

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The Tieqiao reef is well exposed on an extensive 30-metre-wide rock platform along the northern bank of the Hongshui River (Fig. 1C). The core of the mound is well exposed and approximately 20 m in width. While the southern flank is well

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exposed, the full width of reef is unknown because the northern flank is partly

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covered by recent sediments. The reef core is composed of massive limestone, up to

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90 m thick. Laterally the northern edges of the reef core are intercalated with flanking, distally thinning, thin- to medium-bedded limestone. The reef is underlain by a 50

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metre-thick package composed of thinly to medium bedded (0.1‒0.2 m) grey

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argillaceous limestone, brown chert, and siliceous mudstone. A 30-metre-thick,

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4.2.Reef facies association

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medium- to thin-bedded limestone caps the reef.

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Four reef facies associations are recognized: two associations characterize the reef

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base and reef core respectively, one association includes both the northern (windward) and southern (leeward) flank, and one association includes the reef-capping facies (Fig. 2). Table 1 summarizes the petrology and allochem characteristics of all facies associations.

4.2.1. Reef base facies association

ACCEPTED MANUSCRIPT The reef base package is 30 m thick; individual beds are 5-20 cm thick, and stratigraphically beneath the reef core facies association. Limestone bed has sharp planar tops and bases with siliceous mudstone being intercalated (Fig.3A). Both bioclastic wacke-packstone and horizontal siliceous mudstone characterize this

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microfacies and an irregular erosion surface usually divides them (Fig. 3B-C). The

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former microfacies is composed of medium-bedded wacke-packstone with sponges,

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algae, brachiopods, ostracods, foraminifera, and Tubiphytes (also called Shamovella), while the latteris dominated by bedded cherts, and shows a micritic matrix (about

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80-95%) with a sporadic occurrence of sponge spicules (Fig. 3E) and radiolarians (Fig.

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3F). The facies and faunal assemblages indicate a lower slope to basin margin with a lower energy environment interpreted to have formed below storm wave base (Flügel,

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2004).

4.2.2. Reef core facies association

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Diverse sponges which are composed of colonies of five calcareous and

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branching sponge genera: Sphinctozoan sponges Sollasia (Fig. 4A-B), Parauvanela (Fig. 4C-D) and Amblysiphonella (Fig. 4F-G), inozoan sponges and Peronidella (Fig. 4E), and SclerospongiaTabulozoa (Fig. 4I) dominate the reef core facies; macro-algae are the second main fossils, which usually encrust other skeletons (Fig. 4A) with some corals, crinoids also occurring in the field (Fig. 4H).This association is composed of four microfacies types, namely sponge-algae framestone, Sollasia floatstone, sponge-algae boundstone, and skeletonal packstone-grainstone.

ACCEPTED MANUSCRIPT Sponge-algae framestone is in massive limestone forming a major part of the skeletal reef. Bioclasts occupy 50-80% of entire rock (Fig. 5). The sponges Peronidella (Fig. 5A, E) and Permocalculus (Fig. 5D, F) are the most abundant genera observed in thin sections along with minor constituents of fragmented

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Tabulozoa (Fig. 5A), Amblysiphonella (Fig. 5B), and Anthracoporella (Fig. 5C).

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Sponges formed rigid, irregular hill-like bulbous masses, which trapped lime mud.

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Thus these calcisponges and algae are the principal frame constructors of the Permian reefs, as reported from other regions (Rigby et al., 1988, 1989, 1994; Fan et al., 1989,

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1990; Rigby and Senowbari-Daryan, 1996; Wahlman, 2002). Fossil fragments are

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preserved in relatively good states and are less abraded, but disorderly in orientation. These features point to an open, moderate-energy marine environment.

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Sollasia floatstone is grey medium- to thick bedded (20-50cm) bioclastic

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limestone in the field. Micrite dominates the matrix with bioclast contents varying from 30% to 50% of the entire rock. The sphinctozoan sponge Sollasia dominates the

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allochem with minor contributions by algae and foraminifers (Fig. 6B). Geopetal

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structures inside the Sollasia chambers show up direction (Fig. 6A). These Sollasia fossils appear to float within dark coloured muddy matrix (Fig. 6C-E), implying a relatively lower energy niche below storm wave base. Sponge-algae boundstone features with poorly sorted heterogeneous fabrics include a diverse range of bioclasts, predominantly inozoan sponges Peronidella (Fig. 7B, E), Sclerospongia Tabulozoa (Fig. 7B), algae Anthracoporella (Fig. 7A, F), Gymnocodium (Fig. 7D), and encruster Archaeolithoporella (Fig. 7F), with minor constituents of bryozoan and echinoderm

ACCEPTED MANUSCRIPT fragments. Archaeolithoporella is the principal encruster, and forms irregular laminae, which are composed of densely stacked filamentous tubes (Fig. 7C). This allochem assemblage is disarticulated, fragmented, and moderately abraded, suggesting a shallow, stormy environment near fair-weather wave action zone.

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The skeletal pack-grainstone facies in this association is comprised of grey

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medium- to thick-bedded limestone. It is characterized by grainstone textures, with

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locally a packstone texture. Calcareous algae Permocalculus (Fig. 8B) and

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Gymnocodium (Fig.8D), and sponge Peronidella (Fig. 8C, E) dominate the fragments, with minor constituents of Tubiphytes (Fig. 8A) and brachiopods. The combination of

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sparitic matrix, pack-grainstone texture, and hummocky cross beddings all indicate a

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moderate but episodically high-energy habitat.

4.2.3. Reef flank facies association

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The reef flank facies association consists of two microfacies types, namely reef breccias, grainstone in southern flank (leeward side) and algal bindstone facies on the

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northern flank (windward side).The southern flank is in the back reef. It consists mainly of medium- to thin-bedded southward-thinning bioclastic limestone, intercalated and transitional with the facies of the core reef. The limestones are wacke-packstone and are composed of bioclasts of fragmented sponges and algae in a micritic pack-wackestone matrix (Fig. 9). Three sponge genera including the inozoan sponge Peronidella (Fig. 9B), the sphinctozoan sponges Sollasia (Fig. 9A, B) and

ACCEPTED MANUSCRIPT Parauvanela (Fig. 9A). Sponges in some cases were supported and encrusted by Archaeolithoporella (Fig. 9A, C) and are incrusted by Tubiphytes (Fig. 9B). The fossils and facies types strengthen an interpretation as a reef back area (Rigby et al., 1988, 1989, 1994; Fan et al., 1989, 1990; Wahlman, 2002). The facies of the southern

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flank records deposition in a low-energy environment, below storm wave base.

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The northern flank is situated in the reef front. It consists mainly of

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medium-bedded northward bioclastic limestones with clasts of reef breccia displaying pack-grainstone textures. Echinoderms comprise the major allochems of the

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assemblage along with minor constituents of sponges, algae, Tubiphytes, and

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bryozoans. The preponderance of reef breccias and grainstone textures in the northern flank of the reef suggests higher energy conditions at or close to fair-weather wave

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base.

4.2.4. Reef capping facies association

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The strata capping the reef are composed of mudstone and cherty limestone

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microfacies. The latter is formed by thin-bedded limestone with lenticular chert, containing horizontal laminae. Fossils are relatively rare, and both radiolarians and foraminifera dominate the allochem assemblage. The micrite matrix and mudstone texture indicate a low-energy environment situated below storm-weather wave base. The mudstone microfacies comprises thinly bedded, dark grey limestone. Even fossil fragments are rare in this facies, and a micrite matrix covers ~90% in thin section (Fig. 9E). Among the allochem in this association are whole crinoid stems

ACCEPTED MANUSCRIPT (Fig. 9D). Foraminifers are common and algae occur sporadically in this mudstone facies. Textural features of this microfacies indicate a low-energy environment below storm wave base.

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4.3. SEM Analysis

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Tiny calcisphere aggregations are very abundant in the Tieqiao reef core facies and they are categorized into four morphotypes (Fig. 10). Morphotype 1 is the

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simplest type of calcisphere which is calcareous framboidal micrite sphere, 20-80 µm

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in diameter (Fig. 10A-C). Morphotype 2 includes the radially arranged micrite calcite spheroids, 20-40 µm in diameter (Fig. 10E-G). Morphotype 3 contains calcareous

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micro-organisms that are assigned to Ovummurus and have an ovoid to ellipsoidal

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wall. Its internal chamber is diagonally divided into two equal spaces by a septum-like structure. This microfossil is ~60 µm long and ~30 µm wide. The wall and

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pseudo-septum are ~5.0 µm thick (Fig. 10I). It may represent a microproblematicum,

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of unknown biological affinity (Munnecke et al., 2000). Morphotype4 has calcispheres that comprise micrite calcite nuclei coated with radially arranged coarse-grained sparry calcite (Fig. 10J-K). The nuclei are ~50 µm in diameter, and the ring-like radially coat could be 60-100 µm in thickness (Fig. 10L).

4.4. Carbon and Oxygen isotopes

ACCEPTED MANUSCRIPT Carbonate δ13C profiles focused on the GLB have been generated for the Tieqiao section (Wang et al., 2004; Kaiho et al., 2005; Tierney, 2010; Yan et al., 2013). Here we display a δ13C profile focused on the Tieqiao reef system and the analytical results are tabulated in online supplementary data (Table S1). The δ13C values moderately

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fluctuate near +2.2‰ in J. prexuanhanensis zone to J. xuanhanensis zone (late

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Capitation), then abruptly decrease to near 0‰ in J. granti zone and following this

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bounce back to near +2.3‰ in C. hongshuiensis zone. The main negative δ13C excursion starts from the C. hongshuiensis zone (latest Capitanian) to C. postbitteri

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zone (earliest Wuchiapingian), when δ13C values drop 4.7‰ to the trough at near –2.5‰

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(Fig. 11). In the C. dukouensis to C. liangshanensis zones, the C-isotope profile slowly increases to near +4.5‰, then is steady near +4.5‰ with no detectable

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C-isotope perturbation during late C. liangshanensis to middle C. orientalis zones.

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Finally, the δ13C values slightly decrease at the end of the section (late C. orientalis zone). Oxygen isotope values at Tieqiao vary between –9.9‰ and –5.41‰, and there

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is no apparent stratigraphic trend in δ18O at this section.

Discussion

5.1 Comparisons with coeval and Wuchiapingian reef elsewhere in the world

The Wuchiapingian reefs are confined mainly to Boreal Seaand eastern Palaeo-Tethys, namely the Zechstein basin (Central Europe) and Yangtze Platform

ACCEPTED MANUSCRIPT (South China), although they are also sporadically reported from other regions (i.e., Far-Eastern Russia, Kotlyar et al., 1989, 1999). The Zechestein basin is a large basin which ranges from northeast UK in the west to the Belarus in the east and with its north from Denmark, ends at South Germany to its south. Wuchiapingian reef sites

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are distributed around this basin, including northeastern UK (Smith, 1981a, 1981b),

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Abenra in Denmark (Stemmerikand Frymann, 1989), western Poland (Peryt, 1978;

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Dyjaczynski, 2001; Hara et al., 2013; Peryt et al., 2016), and the southern Permian basin (Ernst, 2001; Paul, 2010).

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The Wuchiapingian reefs in the northeastern UK developed mainly in lower and

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middle parts of the Zechstein Limestone. The reef mound in the lower Zechstein Limestone consists of roughly circular or oval patch-reefs, accumulated by untidy

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assemblages of sack-shaped bodies, each composed mainly of closely-packed

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sub-parallel remains of ramose bryozoans Acanthocladia and Thamniscus in a finely crystalline dolomite matrix. Bryozoans die out in the upper reef where algal

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stromatolitic dolomite predominates (Smith, 1981a). The reef mound in middle

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Zechstein Limestone is similar to the former, which founded on a patchy lenticular coquina, unbedded bryozoan biolithite, formed the lower part. Middle stage of reef mound growth is characterized by a progressive increase in the proportion of algal rocks and laminar organic or inorganic encrustations at the expense of the bryozoans, and in the upper part are overlain by an extensive stromatolite biostrome (Smith, 1981b). Most of Wuchiapingian reefs in Germany, Poland, and Denmark also are of

ACCEPTED MANUSCRIPT stromatolite-bryozoan compositions,formed by the bryozoans Acanthocladia and Fenestella in the reef core facies which are replaced by stromatolite in the upper part. The one exception to this rule is found in the Harz Mountains (central Germany), which is an algal stromatolite reef without bryozoans and crinoids (Paul, 1980).A

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Wuchiapingian reef was also observed in Chandalaz Formation in Primorye,

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Far-Eastern Russia, which is dominated by sphinctozoan sponges, together with some

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foraminifera, corals, brachiopods, bivalves, ammonoids, conodonts, crinoids, bryozoans and algae. Massive or irregular spherical tabulate corals, 5-30 cm in

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diameter, occurred in the reef (Kotlyar et al., 1989, 1999).

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In South China, only three Wuchipingian bioconstructions have been reported. The first one is the early Wuchiapingian coral biostrome developed in the lower

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Jiyaopo Formation at the Qincaiyuan section, Ziyun county, Guizhou Province. Four

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coral biostromes were constructed by rugose Liangshanophyllum, Pseudohuangia and Ipciphyllum in Qincaiyuan (Wang et al., 1994; Shen and Xu, 2005). Coral colonies

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here are densely packed with corallites in contact with each other, while microbial

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encrusters are common in these coral biostromes (Shen and Xu, 2005). A second is found in Hanlong county, Guizhou. Here biostromes are composed of rugose corals and Tubiphytes (Lehrmann, 1993). They appear quite similar to the Qincaiyuan biostrome. A third example is the Tieqiao reef. There the dominate reef constructer consists of diverse and abundant sponges, of which more than 15 genera were identified (Yang, 1987), and these contribute 20-65% of the fossil assemblage. Another constructer of

ACCEPTED MANUSCRIPT the reef framework is macro-algae (i.e., Permocalculus). Archaeolithporella, Tubiphytes, and other microbes are the binders/encrusters which strengthened the sponge-algae framework. Unlike Zechstein reefs, microbial organisms didn’t dominate the Tieqiao reef, and bryozoans, which always are a main constructer in the

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Zechstein reefs, are simply dwellers along with echinoderms, brachiopods, and

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gastropods. Also a dolomite matrix, characteristic of Zechstein reefs, was not

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developed in the Tieqiao reef.

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5.2. Restoration of reef ecosystems in the aftermath of the GLB mass extinction

Guadalupian reefs before the extinction were globally distributed, ranging

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longitudinally from the western Pangea margin to the eastern Palaeo-Tethys and

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palaeo-latitudinally from Oman (31°S) to the Nordkapp Basin (38°N) (Flügel and Kiessling, 2002). The GLB reef biotic crisis reduced 88.7% of the reef carbonate

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production and 47% of the number of reefs. It thus represents a second-order reef

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crisis (Flügel and Kiessling, 2002). Reef carbonate production was not completely restored until Changhsingian time, some seven million years after the onset of the crisis (Flügel and Kiessling, 2002). The Wuchiapingian time interval for reefs was characterized by a depauperate reef biota with only five metazoan bioconstructions found in the PaleoReefs Database (Kiessling et al., 2003). Global reef data also indicate a moderate but significant decline in reef-builder diversity (48%) associated with the GLB reef crisis (Flügel and Kiessling, 2002).

ACCEPTED MANUSCRIPT In general, skeleton-dominated bioconstructions are rare in the Wuchiapingian, whereas microbes are the major components of bioconstructions. Reefs or reef mounds in the Zechstein Limestone usually are dominated by microbe-related organisms, and the coral-dominated biostromes in South China never developed into

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true reefs before they started to decline. This likely was due to unfavourable events

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which occurred during the reef-building process (Riding, 2002), resulting in the

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degradation of reefs after the GLB crisis.

Microbial carbonates flourished globally in the aftermaths of major mass

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extinctions such as that of the Frasnian‒Famennian and the Permian‒Triassic, when

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metazoan diversity was low (Riding, 2006). Microbial carbonate resurgence also occurred regionally after the end-Ordovician and end-Triassic extinction events

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(Sheehan and Harris, 2004). Proliferation of microbial carbonates was generally

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attributed to reduced competition from multicellular organisms or relaxed ecological conditions after mass extinctions. Such changes would lower levels of grazing and/or

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bioturbation of microbial communities (Schubert and Bottjer, 1992; Sheehan and

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Harris, 2004), which immediately refilled the vacated ecospace lost by metazoans (Chen and Benton, 2012). In Tieqiao section, deep water radiolarian-dominate fossil assemblage replaced diverse shallow water reef mound fossil assemblage during the GLB crisis. With the sea-level fall in early-middle Wuchiapingian time, reef-building metazoan sponges, together with other benthos such as crinoids, foraminifera, and brachiopods (Fig. 11) reoccur in the middle part of the Heshan Formation. This is calibrated by the

ACCEPTED MANUSCRIPT C. liangshanensis conodont zone, which occurs about 1.5 Myr after the GLB crisis, based on the biochronostratigraphic framework of Ogg et al. (2016). The sponge-algae reef did not occur until the middle-upper part of the Heshan Formation, bracketing to the C. orientalis zone. The Tieqiao sponge-algae reef therefore might be

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the earliest metazoan skeleton-dominated true reef after the GLB crisis, and its

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recovery was much more delayed than that of other level-bottom communities (i.e.,

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brachiopods; Chen et al., 2005; Shen and Zhang, 2008; Shen and Shi, 2009). This likely was because reefs, being fragile and complex ecosystems, required much more

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recovery time, independent of both the reef organisms affected by the crises and of the

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intensity of the crises (Flügel and Kiessling, 2002). Sponges as a pioneer reef builder in the aftermath of mass extinctions also occur in the Early Triassic (Brayard et al.,

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2011) and might be explained by the stress-tolerant nature of the species. Apparently,

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the reestablishment of metazoan reef ecosystems following the GLB mass extinction was a gradual process and one that continued through much of the Wuchiapingian

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time. The reappearance of metazoan reef often serves as marker for the end of the

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recovery (Erwin, 2011). Accordingly, the Tieqiao sponge-algal reef might represent the final recovery of reef ecosystems from the GLB crisis and was succeeded by a reef radiation in the following Changhsingian in South China (Gong et al., 2013).

5.3. Environmental controls on recovery of post-extinction reef ecosystems

Modern coral reefs are usually very fragile and easily destroyed by minor

ACCEPTED MANUSCRIPT variations of marine physical conditions and geochemistry such as sea surface temperature, salinity, pH, redox condition, sea-level change (Hoegh-Guldber and Smith, 1989, 2007; Muscatine et al., 1991;Birkeland, 1996; Spalding et al., 2001; Zhu et al., 2004;DèAth et al., 2009). Similarly, most of these parameters also are crucial in

Carbon isotopic constraints on rebuilding of reef ecosystems following the

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5.3.1

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determining both the growth and demise of deep time reef ecosystems.

GLB crisis

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In Tieqiao, the late Capitanian δ13C values during the J. prexuanhanensis to J.

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xuanhanensis zones remained relatively stable (+1.81-2.87 ‰). The large carbon cycle perturbation occurred in the interval between J. granti zone (latest Capitanian)

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and C. postbitteri zone (earliest Wuchiapingian), when two negative shifts are

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observed. The first shifting is a minor negative excursion when δ13C values dropped 2.3‰ in J. granti zone. The second is the main negative excursion corresponding to

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the C. postbitteri zone when δ13C values declined 4.7‰, coinciding with the GLB

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mass extinction (Fig. 11). The pattern of double negative shifts before and after the GLB were observed only in Tieqiao and Penglaitan sections in South China and Köserelik Tepe section in Turkey (Jost et al., 2014). As first the negative shift is very minor, it could be due to diagenesis. Alternatively, only one negative excursion was recognized in the strata just below the GLB in other sections in South China (Wignall et al., 2009b; Shen et al., 2013). In addition, some workers observed four negative excursions just before the GLB boundary in the Chaotian section, South China (Saitoh

ACCEPTED MANUSCRIPT et al., 2013). Some sections from Japan, Turkey, and Iran yield more minor or undetectable excursions around the GLB (Isozaki et al. 2007; Shen et al., 2013; Jost et al., 2014). So whether the excursions result from local or global control as well as the timing of these excursions remain unresolved (Shen et al., 2013).

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The post-extinction carbon isotopic excursions (calibrated to the C. dukouensis

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zone to the top of C. liangshanensis zone) underwent several positive to negative

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shifting cycles, with δ13C values gradually positive shifting to near +4.5‰ from the C. dukouensis zone to middle part of C. asymmetrica zone, then negatively shifting again

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during the late C. asymmetrica zone. Such negative-positive shifting cycles repeated

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numerous times until the end of the C. liangshanensis zone. δ13C values eventually became relatively stable spanning almost entire C. orientalis zone, with minor

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variations around +4.5‰, although the same excursion tended to shift negatively at

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the end of the same conodont zone (late Wuchiapingian) (Fig. 11). The δ13C excursions over the GLB transition overall appear similar pattern to

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those across the Permian‒Triassic boundary. Mass extinction events in the marine

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environment always are associated with large carbon cycle perturbations, indicating a disturbance. The frequent negative-positive shifting cycles of δ13C also characterize the aftermath of the Permian‒Triassic mass extinction (Payne et al., 2004). Although the true causes of negative-positive shifting cycles of δ13C excursions remaining enigmatic (Payne and Kump, 2007), the dramatic carbon cycle perturbations during the Early Triassic are usually interpreted as indicating a disturbances of the marine environment and ecosystems during initial biotic recovery stage following the

ACCEPTED MANUSCRIPT end-Permian biocrisis. In contrast, a stabilized δ13C excursion is found with the biotic recovery that established the metazoan reef ecosystems during the early Middle Triassic (Payne et al., 2004, 2006). Some metazoans occurred in association with unstable carbon cycles during the early Wuchiapingian, but similarly the

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re-emergence of metazoan reef is concurrent with middle-late Wuchiapingian (C.

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orientalis zone), when δ13C values finally stabilized after the GLB crisis. This

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indicates that the reef ecosystem was fully restored to a favourable condition during the middle-late Wuchiapingian, ~2.5 Myr after the GLB crisis (Fig. 11) (following the

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Sea surface temperature (SST)

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5.3.2

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time-scale of Ogg et al. 2016).

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Results of oxygen isotopes of gondollelid conodont bioapatite from the Tieqiao and Penglaitan sections show that SST elevated about 4 ℃ in late Capitanian

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towards the end of this epoch, ranging from the J. postserratazone to J. granti zone.

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Surprisingly it declined 6-8 ℃ across the GLB boundary (to the earliest Wuchiapingian), ranging from C. postbitteri zone to C. asymmetrica zone), then increased significantly 6-8 ℃ in the middle Wuchiapingian (C. leveni to C. liangshanensis zone), then finally cooled and remained 29-31 ℃ during most s of the middle-late Wuchiapingian time (middle part of C. orientaliszone) (Chen et al., 2011). Oxygen isotopes of conodonts from the Dukou and Jiangya section indicate a persistently slow paced cooling in the middle to late Wuchiapingian (C. orientalis

ACCEPTED MANUSCRIPT zone) (Chen et al., 2013) (Fig. 11). The question is what caused the warming. Some mechanisms have been proposed. The warming in the late Capitanian could be related to the eruption of the Emeishan Large Igneous Province (ELIP) which extended over >0.5×106 km2 in southwest

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China (Courtillot and Renne, 2003). The significant temperature decrease of 6-8 ℃

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across the GLB boundary and in earliest Wuchiapingian time might be attributed to

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ELIP. Rapid release of huge amounts of volatiles (e.g. SO2) from Emeishan into the atmosphere may have absorbed and reflected solar radiation, causing a temperature

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decrease and eventually climate cooling (Zhang et al., 2013). Deep post-eruption

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weathering of the continental effusive basalts (Yang et al., 2015) also likely contributed to climatic cooling by lowering atmospheric pCO2 (Suchet et al., 1995).

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Starting with the C. dukouensis zone temperatures increased again with relatively high

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temperatures between 33 ℃ and 36 ℃ recorded in the C. leveni and C. liangshanensis zones (Chen et al., 2011), coincident with sea level shallowing and

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development of a platform (Shen et al., 2007). An alternative explanation for this

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observed variation in δ18O and palaeotemperature are changes in water depth in conjunction with eustatic sea-level changes (Chen et al., 2011). Finally, decreasing temperatures in the late Wuchiapingian coincides with the Wuchiapingian to Changhsingian transgression detected in the Palaeo-Tethys areas and from the South China block (Chen et al., 1998). As a consequence, Clarkina (or Neogondolella) may have moved to deeper and thus cooler waters. Above all, the variations in the oxygen isotope ratios may reflect a combined effect of changes in water depth and volcanism

ACCEPTED MANUSCRIPT (Chen et al., 2011). Studies of Carboniferous reefs in South China show good correlation between reef recovery and climate warming (Yao and Wang, 2016). Guadalupian reefs flourished in a reef zone of 30°N and 30°S, but Lopingian reefs were restricted to a

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narrow equatorial zone of 20°N and 20°S (Weidlich, 2002a) and a detailed conodont

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δ18O curve (Chen et al., 2013) shows that palaeotemperature continued to rise during

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the Guadalupian and significantly decreased during the Lopingian, suggesting the warm climate supported reef dispersion. However, in Tieqiao section, the

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reemergence of metazoan reef was coincident with decreased palaeotemperatures (Fig.

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11). Based on the studies of modern examples, coral reefs are restricted to a narrow temperature range (20-28 ℃). If the temperature is either too hot it would likely lead

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to reef bleaching as has been observed (Coles and Fadlallah, 1991). During the Late

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Permian, the Laibin area was located in low-latitude region (<5°S) (Ziegler et al., 1998; Wang and Jin, 2000). Thus, SST cooling during the late Wuchiapingian to

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Changhsingian seems not to have negatively impacted the marine ecosystems of the

5.3.3

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Laibin area, perhaps because they remained in a zone of warm, tropical seawater.

Sea-level change

In the basal part of the section, the radiolarian-bearing chert and bedded grey fine-grained limestone of the upper Maokou Formation (Beds 117-118) records deposition in a deep, low-energy basin transition to a lower distal slope setting (Chen

ACCEPTED MANUSCRIPT et al., 2009). The uppermost of Maokou Formation is the Laibin Limestone, comprised of two phases, one formed by the debris-flow facies in the lower part and the other in the upper part, is the core-mound facies.They are interpreted as two up-shallowing packages developed at the end of Guadalupian time (Chen et al., 2009).

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The onset of a drop in sea-level is well-calibrated in the J. xuanhanensis zone and it

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fell in the lowermost in J. granti zone, eventually terminating the mound growth at

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this section (Chen et al., 2009). This dramatic drop in sea-level is interpreted to record a global regression, which resulted in the reduction of the late Permian epeiric sea in

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the Palaeo-Tethys region. After the end-Guadalupian global regression, in the earliest

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Lopingian time a transgression occurred around the Palaeo-Tethys region (Chen et al., 1998) and this event is recorded globally (Haq and Schutter, 2008). The response to

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this global transgression is recorded by in the occurrence of about 40 metres of brown,

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bedded radiolarian chert in the basal Heshan Formation at the Tieqiao section. This indicates an immediate deepening during the time represented from the C. postbitteri

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to C. asymmetrica zones. Beds 112-128 are characterized by bioclastic limestone

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interceded with bedded radiolarian chert, but the chert decreases upward in the section. This suggests that relative sea-level broadly was dropping from the C. leveni to the C. liangshanensis zones, with frequent small-scale transgressions. Owing to the decrease in water depth, the previous lower slope or basin settings became favourable for the recovery of benthic fauna such as sponges, algae, brachiopods, and crinoids (Fig. 11) that formed the bioclastic substrate suitable for reef growth. Beds 129-133 represent metazoan reef growth/recovery after the GLB crisis, predominately by changes in the

ACCEPTED MANUSCRIPT reef core and reef flank facies. As reef continued to grow, dolomite or dolomitized limestone occurs in the uppermost Bed 133. This, together with submarine erosion, indicates a relatively shallow setting. Thus, the Wuchiapingian metazoan reef was grew during a drop in relative sea-level and was terminated by a limitation of space.

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Bed 134 characterized by grey thin bedded limestone or with cherty lenticular,

Conclusions

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6.

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suggests another sea-level rise afterwards.

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The Wuchiapingian sponge-algae reef at Tieqiao section in Guangxi Province, South China, comprises a range of grain-wackestone to cherty limestone-bedding

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chert facies together with bound-floatstone facies. Sponges and algae acted as reef

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builders which colonized skeletal debris on the ramp and initiated reef growth. A diverse community comprising reef dwellers and constructors proliferated in the

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Tieqiao reef complex. After the GLB crisis, bioconstruction usually was dominated by

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microbes, however the Tieqiao reef is the first metazoan reef in the Wuchiapingian, which might represent the final recovery of reef ecosystems following the GLB crisis. Moderate palaeotemperature changes do not seem to have had a strong control on the Tieqiao reef, most likely because the Laibin area was located in equatorial zone with a suitable temperature range for reef growth.~2.5 Myr after the GLB crisis, the reef began when δ13C finally stabilized and resulted in stable geochemical conditions for the reef ecosystem to flourish. Post-extinction restoration of reef ecosystems during

ACCEPTED MANUSCRIPT the middle‒late Wuchiapingian was also associated with a drop in relative sea-level.

Acknowledgments We thank both Tadeusz Peryt and an anonymous reviewer, and guest editor Thomas

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Algeo for critical comments and constructive suggestions, which have improved

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greatly the quality of this paper. This study was supported two NSFC grants

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(41473006, 41572091, 41673011) and grants from the State Key Laboratory of Biogeology and Environmental Geology (GBL11206) and the State Key Laboratory

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of Geological Processes and Mineral Resources (GPMR201504). It is a contribution

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to IGCP 630.

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Fig. 1. (A), Late Permian global palaeogeographic configuration (base map courtesy of R. Blakey (https://www2.nau.edu/rcb7/260moll.jpg)). (B),

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Wuchiapingianpalaeogeographic configuration of South China (modified from Wang

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and Jin 2000; Shen et al. 2007). ELIP = Emeishan large igneous province, dashed line

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shows the modern outcrop area of ELIP (Ali et al., 2002). (C), Geological map

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showing the location of the Tieqiao section (modified from Jin et al., 2006).

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Fig. 2.Stratigraphy, lithology and facies for the late Capitanian to late Wuchiapingian succession at the Tieqiao section.Conodont and fusulinid zones from Mei et al.

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(1998), Jin et al. (2006), and Shen et al. (2007).

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Fig. 3.Reef base facies. (A), Limestone intercalated with siliceous mudstone. (B-C), Siliceous mudstone (lower) and bioclastic limestone (upper) divided by erosion

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surface. (D), Limestone with lenticular chert. (E), Sponge spicule. (F), SEM image showing close-up of one radiolarian.

Fig. 4.Reef core facies. (A), Sollasia encrusted by algae. (B), Sollasia floatstone, (C-D), SphinctozoaParauvanella. (E), InozoanPeronidella. (F-G), SphinctozoaAmblysiphonella. (H), Rugose coral. (I), SclerospongiaTabulozoa.

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Fig. 5.Sponge-Algae framestone facies. (A-B), In situ sponge Tabulozoa (Ta), Peronidella(Pe) and Amblysiphonella(Am). (C-D), Calcareous green algae Anthracoporella (An) and calcareous red algae Permocalculus(Pc). (E),

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Peronidellapackstone. (F), Permocalculusgrainstone.

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Fig. 6.Sollasia floatstone facies. (A), Geopetal structure inside the Sollasia (So)

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chambers. (B), Sollasiaand fusulinid (Fu). (C-E), Sollasiawackestone.

Fig. 7.Sponge-Algalboundstone facies. (A), Sponge-Algalboundstone. (B), Close-up

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of Tabulozoa and Peronidella. (C), Close-up of Archaeolithoporella(Ar), composed

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of densely stacked filamentous tubes. (D), Calcareous red algae Gymnocodium (Gy) dominate the algalgrainstone. (E), Close-up of Peronidella. (F), Close-up of

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Archaeolithoporellaencrusting Tabulozoa and Anthracoporella.

Fig. 8.Skeleton pack-grainstone facies. (A-B), Skeleton grainstone composed of fragments of Tabulozoa, Tubiphytes (Tu) and Anthracoporella, Archaeolithoporellaencrusting fragments or fill the space between fragments. (C-E), Skeleton packstone composed of fragments of Peronidella, Permocalculus,and Gymnocodium.

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Fig. 9.Algalbindstone and mudstone facies.(A-B), Sollasia,Parauvanela, and Permocalculusencrusted by Archaeolithoporella. (C), Bioclastpackstone. (D-E),

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Mudstone facies with minor constituents of crinoid stems.

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Fig. 10. SEM images of different spheroidal aggregates. (A-D), Calcareous framboidal micrite spheroid. (E-H), Radially arranged micrite calcite spheroid. (I),

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Ovummurus. (J-L), Calcispheres comprise micrite nuclei and coated with radially

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arranged coarse-grained sparry calcite. Scale bar 30 μm.

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Fig. 11.Covariations between stratigraphic distribution of major biota, relative sea-level change, carbon isotope excursions and sea surface temperatures (Chen et al.,

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2013).

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Table 1 Facies distributions in the WuchiapingianTieqiao reef, showing key features (rock color, texture, sedimentary structures, autochthonous and allochthonous assemblages), and possible environmental interpretations.

Appendix: Table S1 δ13C and δ18O analytical data from the Tieqiao section.

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Table 1 Facies distributions in the Wuchiapingiuan Tieqiao reef, showing key features (rock colour, texture, sedimentary structures, autochthonous and allochthonous assemblages), and possible environmental interpretations. Facies

Colour/Texture/Structure

Fossil assemblages

Reef base facies association (Beds 122-132)

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Bioclast wackestone-packstone

Grey, wackestone-packstone, medium-bedded

DA: sponges and algae

Siliceous mudstone

Black, thin-bedded, horizontal laminae

DA: sponge spicules and radiolarians.

Reef core facies association (Beds 133) Sollasia floatstone

U N

C C

A

Interpretation

Low

Lower slope

Very low

Basinal margin

Moderate to low

Below SWAZ

High to moderate

Near FWWAZ

Moderate

Close to SWAZ

MA: brachiopods, ostracods, foraminifera.

MA: none.

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Grey, wackstone-packstone, medium-thick bedded

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Energy

A M

DA: Sollasia MA: algae, foraminifera

Sponge-Algae boundstone

Light grey, framestone,

DA: sponges, algae

massive beds

MA: echinoderms, bryozoans

Sponge-Algae

Light grey, grainstone,

DA: sponges, algae

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framestone

medium-thick bedded

MA: corals, bryozoans, echinoderms

Skeleton packstone-grainstone

Grey, packstone- grainstone, medium-thick bedded

DA: sponges, algae

I R

Reef breccias grainstone

DA: Algae, Tubiphytes, sponges,

Light grey, packstone-grainstone,

DA: echinoderms

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Reef capping facies association (Bed 134)

Cherty limestone

Dark-grey, mudstone, thin-bedded

A

C C

Brown, marlstone, thin-bedded with lenticular chert

Low

Below SWAZ

U N

High

Within FWWAZ

A M

Low

Below SWAZ

Low

Below SWAZ

MA: bryozoans, algae, Tubiphytes,

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medium-bedded

Mudstone

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Grey, wackstone-packstone, medium- to thin- bedded

MA: echinoderms, gastropods

SWAZ to FWWAZ

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MA: Tubiphytes, brachiopods

Reef flank facies association (Bed 133) Algae bindstone

Moderate, episodically high

DA: echinoderms MA: bryozoans, algae, Tubiphytes, DA: radiolarian and foraminifera MA: gastropod

DA, dominant fossil assemblages; MA, minor fossil assemblages; FWWAZ, fair-weather wave action zone; SWAZ, storm wave action zone.

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Highlights

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A diverse reef dwellers and constructors community proliferated in the Tieqiao reef Tieqiao reef may show the final recovery of reef ecosystems after the GLB crisis.

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Moderate temperature changes do not have had a strong control on the Tieqiao

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reef.

The reef began when δ13C finally stabilized following the GLB crisis.

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Post-extinction restoration of reef ecosystems was associated with sea-level fall.

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