2. School of Earth Sciences, China University of Geosciences, Wuhan 430074, China
The Pagoda Formation, a lithologically and palaeontologically unique unit among the Upper Ordovician formations (Chen et al., 2010; Zhan and Jin, 2007; Zeng et al., 1983), is characterized by distinctive nodular limestone and abundant fossil assemblages (Fang et al., 2015; Zhou and Zhou, 2005; Sun, 1988; An et al., 1985; Wang et al., 1983). The formation is widely distributed in the Middle and Upper Yangtze area, covering thousands of square kilometers (Zhan et al., 2016a; Xu et al., 2001). Owing to its distinctive lithology and wide distribution, the Pagoda Formation is regarded as an important stratigraphic marker unit of the Ordovician in South China (Zhan et al., 2016b). Also, global stratigraphic correlation of the Pagoda Formation is possible because of the recognition of the Guttenberg δ13C Excursion (GICE) (Bergström et al., 2010, 2009, 2007a, b), the most well-known carbon isotope excursion in the Lower Palaeozoic deposits (Fan et al., 2015; Munnecke et al., 2011).
Despite its worldwide chemo- and litho-stratigraphic correlation, the depositional environment of the Pagoda Formation is still puzzling geologists. It has been interpreted as a low-tide shallow water environment (e.g., Shen, 1989; Chen and Qiu, 1986; Chen and Zhou, 1984; Liu and Chen, 1983), or an open platform environment of relatively deep water below the wave base (e.g., Wang A D, 2012; Xu et al., 2001; Wang Z Z, 1996; Rong and Chen, 1987), or a marine shelf environment of deeper and quieter water (e.g., Zhan et al., 2016a, b; Zhou and Xue, 2000). Meanwhile, the water depth of the Pagoda period is also controversial, ranging from less than 50 m to several hundred meters (Zhan et al., 2016b; Chen et al., 2010; Zhan and Jin, 2007; Ji, 1985).
Remarkably, fossil assemblages of the Pagoda Formation are quite abundant, for instance, trilobites (Zhou et al., 2007; Ji, 1985), brachiopods (Zhan et al., 2002), cephalopods (Fang et al., 2015), conodonts (Wang et al., 2011; An, 1987, 1981), etc. However, detailed reports about other microfossils are limited, i.e., ostracods, radiolarians and foraminifers. Herein, we present well-preserved, relatively thin-shelled ostracods, conodonts, radiolarians and foraminifers from nodular limestone, which diversify fossil assemblages of the Pagoda period. Moreover, these fossil observations also provide palaeontological evidence for discussion of depositional settings.1 GEOLOGICAL SETTING
The Xilingxia Section is located in western Hubei Province, which is tectonically assigned to the northern part of the Yangtze Platform (Fig. 1a). The studied site (30°54′ N, 110°49′ E) is next to No. 334 provincial road, approximately 150 m north of Xilingxia Village in Quyuan Town, Zigui, Hubei Province (Fig. 1b). Before the middle Late Ordovician, the Yangtze Platform was the main carbonate sedimentary region in South China and experienced several evolutionary phases, ranging from the open platform in the Early Ordovician, to the carbonate gentle slope in the Middle Ordovician, and then submerged to carbonate platform in the early–middle Late Ordovician (Zhou et al., 1993). Generally, the eustatic sea-level rise occurred in the early Late Ordovician resulting in the deposition of nodular limestone of the Pagoda Formation (Yan et al., 2008).
The Upper Ordovician succession in the Xilingxia Section includes the Miaopo, Pagoda and Linhsiang formations in ascending order. The Pagoda Formation is characterized by carbonates with benthic shelly faunas (Munnecke et al., 2011). It consists of grayish yellow to purplish red, thick- to medium- bedded limestone, with nodules ranging from 5 cm to nearly 10 cm in diameter. It can be subdivided into two units (Fig. 2). The lower unit, conformably overlying the Miaopo Formation with dark grey shale and intercalated argillaceous limestone, comprises thick-bedded, greyish yellow micritic limestone with nodules (diameters > 5 cm). Cephalopods (Sinoceras) (Fang et al., 2015), the characteristic fossil of the Pagoda Formation, are abundant in this unit. The upper unit, conformably underlying the Linhsiang Formation with argillaceous nodular limestone, consists of medium-bedded, purplish red bioclastic limestone with smaller nodules (diameters < 5 cm).
The Pagoda Formation is dominated by calcareous deposits with bioclastic wackstone observed in thin sections (Zhan et al., 2016a, b). Shelly fossils are extremely abundant, characterized by cephalopods, trilobites, brachiopods and conodonts. Besides, ostracods, foraminifers, corals, echinoderms, etc., are also common but have been rarely reported. As part of the marine community, most of them live in the habitat of deeper water environments (Wang et al., 2011; Zhou et al., 2007; Ji, 1985).2 MATERIAL AND METHODS
Ten nodular limestone samples (approximately 5 kg each) were collected from the Pagoda Formation at the Xilingxia Section. The samples were crushed into fragments (several cubic centimeters each) and divided into two parts. One part was etched in 5%–8% acetic acid solution for one month at room temperature, and the same concentration of acid was added every 3–4 days. The other part utilized the 'hot acetolysis' technique for retrieving the calcareous-shelled ostracods (Crasquin-Soleau and Kershaw, 2005; Lethiers and Crasquin- Soleau, 1988). The fragments were completely dried and then immersed in concentrated (> 99.5%) acetic acid in glass pots. The pots were then placed on a heated sand-bath at a temperature of 60–80 ℃ for 1–2 weeks till adequate muddy residues were deposited. The obtained residues from the two techniques were sieved (20 and 300 meshes) and then dried in a heating cabinet. Subsequently, microfossils were hand-picked from the dried residues with hairbrush or needle under a binocular microscope. Finally, the well-preserved specimens were mounted on stabs and photographed with a scanning electron microscope (SEM).
For this study, 1 126 specimens of conodonts, ostracods, radiolarians and foraminifers were recovered and 513 specimens were photographed. All the specimens and SEM photos were taken at the State Key Laboratory of Geological Process and Mineral Resources of China University of Geosciences (Wuhan).3 RESULTS
The Pagoda assemblages reported herein are of relatively high diversification and good preservation. The samples yield 480 specimens of conodonts from 20 multi-element taxa, and 592 specimens of ostracods from 26 multi-element taxa. Moreover, 29 specimens of foraminifers and 25 specimens of radiolarians were first reported from this formation in South China. Their stratigraphic ranges are showed in Fig. 2.3.1 Conodonts
Conodonts of 15 species and 6 undetermined species from 14 genera are identified (see Fig. 4 and illustration). Amongst them, Hamarodus europaeus Serpagli, 1967, Hamarodus sp., Hamarodus brevirameus Walliser, 1964, Dapsilodus mutatus Branson and Mehl, 1933 and Scabbardella sp. cf. Scabbardella altipes Orchard, 1980 are the dominant species, while Protopanderodus liripipus Kennedy, Barnes and Uyeno, 1979, Ansella baotaensis Ni, 1987, Ansella sp. and Periodon flabellum Lindström, 1955 are also common.
Taxonomically, representatives of Hamarodus, Dapsilodus, Scabbardella and Protopanderodus suggest that the Pagoda conodont assemblage represents the Hamarodus- Dapsilodus-Scabbardella (HDS) biofacies, which show closest affinity to those from the North Atlantic Conodont Province (Ortega et al., 2008; Bergström, 2007; Stouge and Rasmussen, 1996; Savage, 1990). This biofacies are defined by the dominance of Hamarodus, Dapsilodus, Scabbardella (Sweet and Bergström, 1984), which are broadly distributed in the outer shelf and are characteristic of relatively cold water deposits (Ferretti et al., 2014; Wang et al., 2007). In South China, similar conodont assemblage had also been reported from the Pagoda Formation in Shaanxi and Sichuan (Chen and Ji, 1986; Chen, 1983), the Yanwashan Formation in Zhejiang (Wang et al., 2015), and the Tangshan Formation in Anhui (Chen and Zhang, 1989). Whereas, the Pagoda conodonts have kept its local character that enigmatic species Ansella baotaensis, Besselodus sp. etc. only appear in Hubei.3.2 Ostracods
Ostracods of 26 species (16 undetermined species) belonging to 14 genera are identified, composed of Palaeocopida and Metacopida. Amongst them Planoria, Fenxiangia, Schmidtella and Aparchites are the dominant genera, and the specimens of Fenxiangia account for nearly one-tenth as a whole. The Pagoda ostracods are comparable to those from the Craighead limestone formation in Southwest Scotland, which are characterized by Steusloffia dominated association and form a 'high-diversity open marine assemblage', with species of Schmidtella, Steusloffia, Aparchites, Longiscula, Balticella, Medianella, Krausella, etc., and represent outer platform or deep shelf settings (Mohibullah et al., 2010). In South China, similar taxa have been documented from the Pagoda Formation in Fenxiang, Yichang and Liangshan, Shaanxi; the Yanwashan and Sanqushan formations in Jiangshan and Changshan, Zhejiang; with the common occurrence of Aparchites changyangensis, A. chaqiensis, Planoria fenxiangensis, P. zhoutangensis and Fenxiangia sp. (Wang, 2015; Jiang et al., 1995; Yuan and Ma, 1993; Li, 1989; Sun, 1987; Shi and Wang, 1985). Generally, most of them are typical species in the Late Ordovician.
Interestingly, relatively well-preserved radial decorations are recognized on the surface of the thin-shelled Schmidtella sp. (Fig. 4, D–E), which account for approximately a half of this species (30 carapace shells). However, the contributing factor is still unknown. Besides, it is crucial to note that several specimens with spinous ornaments were first reported in South China which is characteristic of relatively deep water environments (Wang, 2015; Zhao et al., 2014; Gou and Peng, 2011). According to carapace morphology, they are temporarily ascribed to? Steusloffia sp. (Mohibullah et al., 2010). The genus Steusloffia with spinous ornaments is less common (Moore, 1961, p. 210).3.3 Radiolarians and Foraminifers
Three radiolarian tests are recognized. One is identified as Armstongisphaera sp. (Fig. 6, A). This genus was first reported by Kozur (1984) from the lower Silurian series of Hungary. The other two tests (Fig. 6, B–C and D–F) are hardly assigned due to poor preservation. The order Spumellaria is dominating the radiolarian assemblage. In South China, studies on the Upper Ordovician radiolarians were limited, with documents only from the Wufeng Formation in Lunshan, Jiangsu (Wang and Zhang, 2011) and Leibo, Sichuan (Liu et al., 2010). Different from that in the Pagoda Formation, the Wufeng fauna was characterized by spherical radiolarians with long slender spines.
Agglutinated foraminifers of 3 undetermined species assigned to 2 genera Lagenammina and Amphitremoida are identified. The assemblage is dominated by thin-walled monothalamous (single-chambered) specimens. They possess regular to irregular rounded internal cavity and one or two conical apertural canals. The Late Ordovician foraminiferal fauna, which has been less known in South China, was first reported from the Pagoda Formation. Similar morphological species have been documented from the Lower to Middle Ordovician in northwestern Russia (Nestell and Tolmacheva, 2004) and Germany (Riegraf and Niemeyer, 1996).4 DISCUSSION 4.1 Biostratigraphical Significance
As noted by An (1987), Chen (1983), Chen and Ji (1986), Wang et al.(2017, 2015, 2011), the conodont Baltoniodus alobatus Zone and Hamarodus europaeus Zone are recognized in ascending order. The base of the Pagoda formation in South China is in the conodont Baltoniodus alobatus Zone (Wang et al., 2011; An, 1987). Whilst the accurate biostratigraphic age of the top of this formation remains uncertain (Chen et al., 2010). In the studied section, only the index species H. europaeus is recognized, along with other species Protopanderodus liripipus, Panderodus gracilis, Cornuodus longibasis, Scabbardella altipes etc. The conodont assemblage suggests that they belong to the H. europaeus Zone, which is typical for the Lower Katian Stage (Ferretti et al., 2014; Wang and Wu, 2009; Bergström et al., 2000; Stouge and Rasmussen, 1996).
Because of close affinity within conodonts from successions in South China and coeval successions in the North Atlantic area (Wang et al., 2015, 2011, 2007; Tolmacheva et al., 2009), inter-continental biostratigraphic correlations between these regions are possible. The Baltoniodus alobatus Zone is equivalent to the B. alobatus Subzone of the A. tvaerensis Zone in the North Atlantic conodont zonation (Wang et al., 2017, 2015, 2011; Bergström, 1971). Besides, it is noted that the Amorphognathus superbus Zone is well recorded in the North Atlantic region, with frequent co-occurrence of species H. europaeus (Fan et al., 2015), thus the H. europaeus Zone can be well correlated to the Amorphognathus superbus Zone. A. superbus Zone was rarely reported from the Pagoda Formation in South China, apart from initially been distinguished by Chen and Zhang (1989) from the Lower Tangshan Formation in Shitai, Anhui.
In South China, similar H. brevirameus Zone was documented from the Yanwashan Formation in Jiangxi and the Tangshan Formation in Anhui, the zonal index species of which is considered as the senior synonym of H. europaeus (e.g., Wang et al., 2015; Ferretti et al., 2014; Dzik, 1994; Chen and Zhang, 1989). Thus, the Yanwashan and part of the Tangshan formations can be well correlated with the Pagoda Formation by the H. europaeus Zone (Wang et al., 2015; Chen et al., 2010).4.2 Palaeoenvironmental Significance
The grayish yellow to purplish red nodular limestone of the Pagoda Formation is widely distributed in the middle and upper Yangtze area. Interpretations of the depositional settings of this formation are mainly based on lithological characteristics (Zhan et al., 2016a, b; Wang et al., 2012; Xu et al., 2001). Herein, more palaeontological evidence will be discussed. Major faunal associations from the Pagoda Formation are common, characterized by smooth and small-shelled Leangella-Foliomena brachiopod association (Rong et al., 1999), the main components of which are commonly found in deeper water environments. Moreover, based on Cyclopyge-Symphysops- Psilacella trilobite association and Sinoceras nautiloid fauna, the minimum depth of 150 m for the Pagoda Formation was proposed (Rong et al., 1999; Wang, 1996).
Sweet and Bergström (1984) initially distinguished conodont Hamarodus-Dapsilodus-Scabbardella (HDS) biofacies widely distributed in the North Atlantic faunal region and suggested relatively cold water deposits (Wang et al., 2015, 2007, 1996; Bergström et al., 2007a, b; Tolmacheva et al., 2009; Stouge and Rasmussen, 1996). The nodular limestone of the Pagoda Formation yields abundant conodonts, which are characterizedby the HDS biofacies. The typical species H. europaeus occurs in relatively deep water sequences of the Northern Europe, Southeast and Northeast Asia, especially in South China (Chen et al., 2010; Zhang and Barnes, 2007; Ferretti and Serpagli, 1999; Dzik, 1994). Besides, Dapsilodus and Scabbardella often co-occurred with Hamarodus. Though these two genera are cosmopolitan and present in various depths, associations with H. europaeus are considered as indicative of deep water facies. Moreover, associated species of genus Periodon were present in outer shelf areas of colder and deeper water environments (Wu et al., 2014; Tolmacheva et al., 2009; Wang et al., 2007). Thus, the Pagoda conodont assemblage may indicate relatively deep and cold water, outer shelf environments.
According to Whatley(1988, 1983), ostracod diversity and assemblage compositions vary with environments. Their morphological features may reflect water temperature and depths, and thus be utilized as environmental indicators (Holms and Chivas, 2002; Casier et al., 2005, 2003). Copeland (1982) recognized aparchitid and schmidtellid rich assemblage from Ordovician Lower Esbataottine Formation in Canada, restricted to a deeper shelf marine environment. Consequently, smooth and thin-shelled Aparchites and Schmitella, as dominating genera of ostracod assemblage from the Pagoda Formation, are regarded as characteristics of quieter and deeper water depositional settings (Mohibullah et al., 2010; Williams and Siveter, 1996; Williams and Vannier, 1995). As for shell ornaments, similar nubbles and spines were typically documented in deep water environments (Si et al., 2010; De Deckker, 2002, De Deckker and Forester, 1998).
Radiolarians are widely reported from siliceous rocks of relatively deep water environments (Feng and Algeo, 2014; Kozur, 1993). Although the radiolarian assemblage in the Pagoda Formation comprises limited specimens that are of lower diversity and abundance, spherical radiolarians with short spines indicate relatively deep water shelf environments (Nie et al., 2012). Besides, the foraminifers' faunal composition of low diversity and species abundance are similar to those from the Siberian region (Nestell et al., 2009; Nestell and Tolmacheva, 2004), which belongs to cold water assemblage. According to their morphological preservation, small and thin-walled fauna could be living in the relatively deep water environments (Dixon and Haig, 2004; Kaiho, 1991). In general, the relatively deep water plankton and benthic shelly faunas are widely preserved in the Pagoda Formation, along with lithological characteristics, which indicates the rselatively cold and deep water of outer shelf depositional settings.5 CONCLUSION
The Pagoda Formation exhibits fossil assemblages of high diversity, with conodonts of 14 genera 20 species (6 undetermined species) and ostracods of 14 genera 26 species (16 undetermined species). In addition, radiolarians and minute- walled foraminifers reported here represent their first records in South China. The occurrence of H. europaeus suggests that the conodont assemblage can be attributed to the Hamarous europaeus Zone, which indicates the Early Katian Age. The conodont HDS Biofacies (Sweet and Berrström, 1984), together with morphological evidence from thin-shelled ostracods, spherical radiolarians and foraminifers, indicate relatively deep and cold water, outer shelf depositional settings, which are in accordance with previous research on lithological characteristics (Zhan et al., 2016a, b). Accordingly, our materials enrich the diversity of the Pagoda biota in South China, and also provide palaeontological evidence for the depositional settings and stratigraphic correlations for the Pagoda Formation.ACKNOWLEDGMENTS
The work was supported by NSFC (No. 41430101). We would like to thank Prof. Galina P. Nestell for the important suggestions of identification of foraminifers. We thank Prof. Renbin Zhan and Dr. Junjun Song for their comments that improve the quality of this paper. We also express our sincere thanks to Miss Maliha Khan for checking English. The final publication is available at Springer via https://doi.org/10.1007/s12583-017-0958-7.
An, T. X., 1981. Recent Progress in Cambrian and Ordovician Conodont Biostratigraphy of China. Geological Society of America, 187: 209-226. DOI:10.1130/SPE187-p209
An, T. X., 1987. Early Paleozoic Conodonts from South China. Beijing University, Beijing: 238.
An, T. X., Du, G. Q., Gao, Q. Q., 1985. Research on Ordovician Conodonts in Hubei Province. Geological Publishing House, Beijing. 33-43.
Bergström, S. M., 1971. Conodont Biostratigraphy of the Middle and Upper Ordovician of Europe and Eastern North America. In: Sweet, W. C., Bergström, S. M., eds., Symposium on Conodont Biostratigraphy. Geological Society of America Memoir, 127: 83-159
Bergström, S. M., 2007. Middle and Upper Ordovician Conodonts from the Fågelsång GSSP, Scania, Southern Sweden. GFF, 129(2): 77-82. DOI:10.1080/11035890701292077
Bergström, S. M., Chen, X., Schmitz, B., et al., 2009. First Documentation of the Ordovician Guttenberg δ13C Excursion (GICE) in Asia: Chemostratigraphy of the Pagoda and Yanwashan Formations in Southeastern China. Geological Magazine, 146(1): 1-11. DOI:10.1017/s0016756808005748
Bergström, S. M., Chen, X., Yong, S. A., et al., 2007a. The First Record of the Ordovician Guttenberg δ13C Excursion (GICE) in Asia: Chemostratigraphy of the Pagoda Limestone and Yanwashan Formation in South-Eastern China. Geological Society of America, Abstracts with Programs, 39(6): 145.
Bergström, S. M., Yong, S., Schmitz, B., et al., 2007b. Upper Ordovician (Katian) δ13C Chemostratigraphy: A Trans-Atlantic Comparison. Acta Palaeontologica Sinica, 46(Suppl): 37-39.
Bergström, S. M., Finney, S. C., Chen, X., et al., 2000. A Proposed Global Boundary Stratotype for the Base of the Upper Series of the Ordovician System: The F?gels?ng Section, Scania, Southern Sweden. Episodes, 23(2): 102-109.
Bergström, S. M., Schmitz, B., Young, S. A., et al., 2010. The δ13C Chemostratigraphy of the Upper Ordovician Mjosa Formation at Furuberget near Hamar, Southeastern Norway: Baltic, Trans-Atlantic, and Chinese Relations. Norwegian Journal of Geology, 90(1/2): 65-78.
Casier, J. G., Préat, A., 2003. Ostracods and Lithofacies of the Devonian-Carboniferous Boundary Beds in the Avesnois, North of France. Bulletin de l'Institut Royal des Sciences Naturelles de Belgique, Science de la Terre, 73: 83-107.
Casier, J. G., Lebon, A., Mamet, B., et al., 2005. Ostracods and Lithofacies Close to the Devonian-Carboniferous Boundary in the Chanxhe and Rivage Sections, Northeastern Part of the Dinant Basin, Belgiqum. Bulletin de l'Institut Royal des Sciences Naturelles de Belgique, Science de la Terre, 75: 95-126.
Chen, M. J., Zhang, J. H., 1984. Middle Ordovician Conodonts from the Yenwashan Formation of the Jiannan Province. Journal of Nanjing University: Geology, 4(Suppl): 149-160.
Chen, M. J., Zhang, J. H., 1989. Ordovician Conodonts from the Shitai Region, Anhui. Acta Micropalaeontologica Sinica, 6(3): 213-228.
Chen, T. E., Zhou, X. P., 1984. On the Baota (Pagoda) Formation. Stratigraphy and Palaeontology of Systemic Boundaries in China, Ordovician-Silurian Boundary (1). Anhui Science and Technology Publishing House, Hefei. 1-10.
Chen, X., Bergström, S. M., Zhang, Y. D., et al., 2010. Upper Ordovician (Sandbian-Katian) Graptolite and Conodont Zonation in the Yangtze Region, China. Earth and Environmental Science Transactions of the Royal Society of Edinburgh, 101(2): 111-134. DOI:10.1017/s1755691010009199
Chen, X., Qiu, J. Y., 1986. Ordovician Palaeoenvironmental Reconstruction of Yichang Area, Western Hubei. Journal of Stratigraphy, 10(1): 1-15.
Chen, Y. H., 1983. Conodonts from Ordovician Pagoda Formation in Guan- yinqiao of Qijiang Country Sichuan Province. Bulletin of the 562 Comprehensive Geological Brigade Chinese Academy of Geological Sciences, 4: 137-139.
Chen, Y. H., Ji, Z. L., 1986. Conodonts from the Pagoda Formation in Liangshan of Nanzhen Country, Shanxi Province. Bulletin of the 562 Comprehensive Geological Brigade Chinese Academy of Geological Sciences, 5: 91-97.
Copeland, M. J., 1982. Bathymetry of Early Middle Ordovician (Chazy) Ostracodes, Lower Esbataottine Formation, District of Mackenzie. Bulletin of the Geological Survey of Canada, 347: 1-39.
Crasquin-Soleau, S., Kershaw, S., 2005. Ostracod Fauna from the Permian- Triassic Boundary Interval of South China (Huaying Mountains, Eastern Sichuan Province): Palaeoenvironmental Significance. Palaeogeography, Palaeoclimatology, Palaeoecology, 217(1/2): 131-141. DOI:10.1016/j.palaeo.2004.11.027
De Deckker, P., 2002. Ostracod Palaeoecology. In: Holmes, J. A., Chivas, A. R., eds., The Ostracoda: Applications in Quaternary Research. American Geophysical Union, Washington D. C. . 121-133
De Deckker, P., Forester, R. M., 1988. The Use of Ostracods to Reconstruct Continental Palaeoenvironmental Records. In: De Deckker, P., Peypouquet, J. P., eds., Ostracoda in the Earth Sciences. Elsevier, Amsterdam. 175-199
Dixon, M., Haig, D. W., 2004. Foraminifera and Their Habitats with a Cool-Water Carbonate Succession Following Glaciations, Early Permian (Sakmarian), Western Australia. Journal of Foraminiferal Research, 34(4): 308-324. DOI:10.2113/34.4.308
Dzik, J., 1994. Conodonts of the Mójcza Limestone: Ordovician Carbonate Platform Ecosystem of the Holy Cross Mountains. Acta Palaeontologica Polonica, 53: 43-128.
Fan, R., Bergström, S. M., Lu, Y. Z., et al., 2015. Upper Ordovician Carbon Isotope Chemostratigraphy on the Yangtze Platform, Southwestern China: Implications for the Correlation of the Guttenberg δ13C Excursion (GICE) and Paleoceanic Change. Palaeogeography, Palaeoclimatology, Palaeoecology, 433: 81-90. DOI:10.1016/j.palaeo.2015.05.016
Fang, X., Zhang, Y. B., Chen, T. E., 2015. Morphological Variation of Cephalopods Sinoceras Chinense (Foord). Acta Palaeontological Sinica, 54(1): 84-92.
Feng, Q. L., Algeo, T. J., 2014. Evolution of Oceanic Redox Conditions during the Permo-Triassic Transition: Evidence from Deepwater Radiolarian Facies. Earth-Science Reviews, 137: 34-51. DOI:10.1016/j.earscirev.2013.12.003
Ferretti, A., Serpagli, E., 1999. Late Ordovician Conodont Faunas from Southern Sardinia, Italy: Biostratigraphic and Paleogeographic Implications. Bollettino della Societ'a Paleontologica Italiana, 37(2/3): 215-236.
Ferretti, A., Messori, A., Bergström, S. M., 2014. Composition and Significance of the Katian (Upper Ordovician) Conodont Fauna of the Vaux Limestone ('Calcaire des Vaux') in Normandy, France. Estonian Journal of Earth Sciences, 63(4): 214-219. DOI:10.3176/earth.2014.21
Gou, Y. X., Peng, J. L., 2011. On the Nodal Ornamentation of Pleistocene Ostracoda from the Zoige Basin, Eastern Qinghai-Xizang (Tibetan) Plateau. Acta Micropalaeontologica Sinica, 28(1): 7-21.
Holms, J. A., Chivas, A. R., 2002. The Ostracoda: Applications in Quaternary Research. American Geophysical Union, Washington D. C. 1-313.
Ji, Z. L., 1985. On the Depositional Environment of the Pagoda Formation in Central and Southwestern China. In: Rong, L. B., ed., Stratigraphy and Paleontology Proceedings (12). Geological Publishing House, Beijing. 91-100 (in Chinese)
Jiang, X. T., Zhou, W. F., Lin, S. P., et al., 1995. Ostracoda in Xinjiang. Geological Publishing House, Beijing. 65-68.
Kaiho, K., 1991. Global Changes of Paleogene Aerobic/anaerobic Benthic Foraminifera and Deep-Sea Circulation. Palaeogeography, Palaeoclimatology, Palaeoecology, 83(1/2/3): 65-85. DOI:10.1016/0031-0182(91)90076-4
Kozur, V. H., 1984. Muellerisphaerida Eine Neus Ordnung Von Mikrofossilien Unbekannter Systematischer Stellung Aus Dem Silur Und Unterdevon Von Ungarn. Geologisch-Pal?ontologis Mitteilungen Innsbruck, 13(6): 125-148.
Kozur, V. H., 1993. Upper Permian Radiolarians from the Sosio Valley Area, Western Sicily (Italy) and from the Uppermost Lamar Limestone of West Texas. Jahrbuch der Geologischen Bundesanstalt Wien., 136: 99-123.
Lethiers, F., Crasquin-Soleau, S., 1988. Comment Extraire des Microfossiles à Tests Calcitiques de Roches Calcaires Dures. Revue de Micropaléontologie, 31: 56-61.
Li, Y. W., 1989. The Discovery of Ordovician Ostracods from Erlang Mountain, Sichuan. Bulletin of the Chengdu Institute of Geology and Mineral Resources, Chinese Academy of Geological Sciences, 10: 131-149.
Liu, T. M., Chen, X. S., 1983. 'Horseshoe-Like Cracks' in the Pagoda Limestone in Northern Guizhou and Discussions on Their Origin. Collected Paper of Stratigraphy and Paleontology of Guizhou, 1: 169-174.
Liu, W., Xu, X. S., Feng, X. T., et al., 2010. Radiolarian Siliceous Rocks and Palaeoenvironmental Reconstruction for the Upper Ordovician Wufeng Formation in the Middle-Upper Yangtze Area. Sedimentary Geology and Tethyan Geology, 30(3): 65-70.
Mohibullah, M., Afzal, J., Williams, M., et al., 2010. Ostracods from Upper Ordovician (Katian) Carbonate Lithofacies in Southwest Scotland. Geological Magazine, 147(6): 919-939. DOI:10.1017/s0016756810000385
Moore, R. C., 1961. Treatise on Invertebrate Paleontology, Part Q: Anthropoda 3, Crustacea Ostracoda. Geological Society of America and University of Kansas Press, Kansas. 442-443.
Munnecke, A., Zhang, Y. D., Liu, X., et al., 2011. Stable Carbon Isotope Stratigraphy in the Ordovician of South China. Palaeogeography, Palaeoclimatology, Palaeoecology, 307(1/2/3/4): 17-43. DOI:10.1016/j.palaeo.2011.04.015
Nestell, G. P., Mestre, A., Heredia, S., 2009. First Ordovician Foraminifera from South America: A Darriwilian (Middle Ordovician) Fauna from the San Juan Formation, Argentina. Micropaleontology, 55(4): 329-344.
Nestell, G. P., Tolmacheva, T. Y., 2004. Early Ordovician Foraminifers from the Lava River Section, Northwestern Russia. Micropaleontology, 50(3): 253-280. DOI:10.2113/50.3.253
Nie, X. M., Lei, Y., Feng, Q. L., 2012. Evolution and Its Control Factors of the Changsingian Radiolarian at the Shangsi Section in Jiange Country, Guangyuan City, Sichuan Province. Geological Review, 58(5): 509-515.
Orchard, M. J., 1980. Upper Ordovician Conodonts from England and Wales. Geologica et Palaeontologica, 14: 9-44.
Ortega, G. L., Albanesi, A. L., Peralta, G. L., 2008. High Resolution Conodont- Graptolite Biostratigraphy in the Middle-Upper Ordovician of the Sierra de La Invernada Formation (Central Precordillera, Argentina). Geologica Acta, 6(2): 161-180. DOI:10.1007/s12583-016-0712-6
Riegraf, W., Niemeyer, J., 1996. Agglutinierte Foraminiferen Aus Graptolithen-Schwarzschiefern des Llanvirnium (Ordovizium) von Plettenberg Im Sauerland (Nordrhein-Westfalen, NW-Deutschland). Paläontologische Zeitschrift, 70(1/2): 19-36. DOI:10.1007/bf02988266
Rong, J. Y., Chen, X., 1987. Faunal Differentiation, Biofacies and Lithofacies Pattern of Late Ordovician (Ashgillian) in South China. Acta Palaeontological Sinica, 26: 507-535.
Rong, J. Y., Zhan, R. B., Harper, D. A. T., 1999. Late Ordovician (Caradoc- Ashgill) Brachiopod Faunas with Foliomena Based on Data from China. Palaios, 14(5): 412-431. DOI:10.2307/3515394
Savage, N. M., 1990. Conodonts from the Late Ordovician Cliefden Caves Limestone, Southeastern Australia. Journal of Paleontology, 64(5): 821-831. DOI:10.1017/S0022336000019016
Shen, J. W., 1989. New Observations of the Origin of Baota Limestone in Guizhou and Its Adjacent Regions. Geology of Guizhou, 6(1): 35-38.
Shi, G. C., Wang, D. H., 1985. Middle Ordovician Ostracods from Huanxian, Gansu. Bulletin of the Xi'an Institute of Geology and Mineral Resources, Chinese Academy of Geological Sciences, 10: 95-106.
Si, W. M., Xi, D. P., Huang, Q. H., et al., 2010. Ostracode Stratigraphy and Palaeoenvironment of the Cretaceous Qingshankou Formation in East Songliao Basin. Acta Geologica Sinica, 84(10): 1389-1400.
Stouge, S., Rasmussen, J. A., 1996. Upper Ordovician Conodonts from Bornholm and Possible Migration Routes in the Palaeotethys Ocean. Bulletin of the Geological Society of Denmark, 43: 54-67.
Sun, Q. Y., 1987. Ostracoda/Biostratigraphy in the Yangtze Gores (2): Early Paleozoic. Geological Publishing House, Beijing: 335-363.
Sun, Q. Y., 1988. Ordovician Ostracods from Western Hubei. Acta Micropalaeontologica Sinica, 5(3): 253-266.
Sweet, W. C., Bergström, S. M., 1984. Conodonts Provinces and Biofacies of the Late Ordovician. Geological Society of America Special Paper, 196: 69-87. DOI:10.1131/SPE196-p69
Tolmacheva, T. Y., Degtyarev, K. E., Ryazantsev, A. V., et al., 2009. Conodonts from the Upper Ordovician Siliceous Rocks of Central Kazakhstan. Paleontological Journal, 43(11): 1498-1512. DOI:10.1134/s0031030109110136
Wang, A. D., 2012. Cause of Reticular Cracks in Ordovician Baota Formation Limestone in Southern Shanxi. Earth Science-Journal of China University of Geolosciences, 37(4): 843-850.
Wang, S. Q., 2015. Ordovician and Silurian Ostracoda of China. University of Science and Technology of China Press, Hefei. 14
Wang, X. F., Zeng, Q. L., Zhou, T. M., et al., 1983. Latest Ordovician and Earliest Silurian Faunas from the Eastern Yangtze Gorges, China with Comments on Ordovician-Silurian Boundary. Bulletin of the Yichang Institute of Geology and Mineral Resources, Chinese Academy of Geological Sciences, 6: 95-163.
Wang, Y. J., Zhang, Y. D., 2011. Radiolarian Fauna of the Wufeng Formation (Upper Ordovician) in Lunshan Area, Jiangsu and Its Geological Significance. Acta Micropalaeologica Sinica, 28(3): 251-260.
Wang, Z. H., Bergström, S. M., Lane, H. R., 1996. Conodont Provinces and Biostratigraphy in Ordovician of China. Acta Palaeontologica Sinica, 35(1): 26-59.
Wang, Z. H., Bergström, S. M., Zhang, Y. D., et al., 2015. Upper Ordovician Conodonts from the Yenwashan Formation in the Zhejiang-Jiangxi Border Region S. E. China and Their Biostratigraphic Significance. Acta Palaeontologica Sinica, 54(2): 147-157.
Wang, Z. H., Qi, Y. P., Bergström, S. M., 2007. Ordovician Conodonts of the Tarim Region, Xinjiang, China: Occurrence and Use as Paleoenvironment Indicators. Journal of Asian Earth Sciences, 29(5/6): 832-843. DOI:10.1016/j.jseaes.2006.05.007
Wang, Z. H., Qi, Y. P., Wu, R. C., 2011. Cambrian and Ordovician Conodonts of China. University of Science and Technology of China Press, Hefei. 91-184.
Wang, Z. H., Wu, R. C., 2009. Ordovician Conodont Diversification of the Lower Yangtze Valley. Acta Micropalaeontologica Sinica, 26(4): 331-350.
Wang, Z. H., Zhen, Y Y., Ma, X., et al., 2017. Middle to Upper Ordovician Conodont Succession from the Qiliao Section of Shizhu, Chongqing-Revealing a Depositional Hiatus between Lower Darriwilian and Sandbian. Acta Palaeontologica Sinica, 56(1): 37-53.
Wang, Z. Z., 1996. Baota Formation: A Middle Ordovician Condensed Section. Sedimentary Facies and Palaeogeography, 16(5): 18-21.
Whatley, R. C., 1983. The Application of Ostracoda to Palaeoenvironmental Analysis. In: Maddocks R. F., ed., Application of Ostracoda. Department of Geosciences University of Houston-University Park Houston, Texas. 51-77
Whatley, R. C., 1988. Population Structure of Ostracods: Some General Principles for the Reconstruction of Palaeoenvironments. In: De Deckker, P, ed., Ostracoda in the Earth Sciences. Elsevier Science Publisher, New York. 245-256
Williams, M., Siveter, D. J., 1996. Lithofacies-Influenced Ostracod Associations in the Middle Ordovician Bromide Formation, Oklahoma, USA. Journal of Micropalaeontology, 15(1): 69-81. DOI:10.1144/jm.15.1.69
Williams, M., Vannier, J. M. C., 1995. Middle Ordovician Aparchitidae and Schmidtellidae: The Significance of 'Featureless' Ostracods. Journal of Micropalaeontology, 14(1): 7-24. DOI:10.1144/jm.14.1.7
Wu, R. C., Stouge, S., Percival, I. G., et al., 2014. Early-Middle Ordovician Conodont Biofacies on the Yangtze Platform Margin, South China: Applications to Palaeoenvironment and Sea-Level Changes. Journal of Asian Earth Sciences, 96: 194-204. DOI:10.1016/j.jseaes.2014.09.003
Xu, X. S., Wan, F., Yin, F. G., 2001. Environment Facies, Ecological Facies and Diagenetic Facies of Baota Formation of Late Ordovician. Journal of Mineral Petrol, 21(3): 64-68.
Yan, D. T., Wang, Q. C., Chen, D. Z., et al., 2008. Sedimentary Environment and Development Controls of the Hydrocarbon Sources Beds: the Upper Ordovician Wufeng Formation and the Lower Silurian Longmaxi Formation in the Yangtze Area. Acta Geological Sinica, 82(3): 321-327.
Yuan, F. T., Ma, L. X., 1993. Middle Ordovician Ostracods from the Baota Formation, Liangshan, Shanxi. Acta Micropalaeontologica Sinica, 10(2): 223-235.
Zeng, Q. L., Ni, S. Z., Xu, G. H., et al., 1983. Subdivision and Correlation on the Ordovician in the Eastern Yangtze Gorges, China. Bulletin of the Yichang Institute of Geology and Mineral Resources, Chinese Academy of Geological Sciences, 6: 1-56.
Zhan, R. B., Jin, J. S., 2007. Ordovician-Early Silurian (Landovery) Stratigraphy and Palaeontology of the Upper Yangtze Plateform, South China. Science Press, Beijing. 55-61.
Zhan, R. B., Jin, J. S., Liu, J. B., et al., 2016a. Meganodular Limestone of the Pagoda Formation: A Time-Specific Carbonate Facies in the Upper Ordovician of South China. Palaeogeography, Palaeoclimatology, Palaeoecology, 448: 349-362. DOI:10.1016/j.palaeo.2015.07.039
Zhan, R. B., Jin, J. S., Liu, J. B., 2016b. Meganodular Limestone Points South China Paleoplate to the Late Ordovician Equator. Acta Geologica Sinica: English Edition, 90(1): 388-389. DOI:10.1111/1755-6724.12668
Zhan, R. B., Rong, J. Y., Jin, J. S., et al., 2002. Late Ordovician Brachiopod Communities of Southeast China. Canadian Journal of Earth Sciences, 39(4): 445-468. DOI:10.1139/e01-094
Zhang, S. X., Barnes, C. R., 2007. Late Ordovician to Early Silurian Conodont Faunas from the Kolyma Terrane, Omulev Mountains, Northeast Russia, and Their Paleobiogeographic Affinity. Journal of Paleontology, 81(3): 490-512. DOI:10.1666/05077.1
Zhao, Q. H., Li, X. Y., Mei, X., et al., 2014. Middle-Late Pleistocene Cold-Water Ostracoda of the Yellow Sea and Bohai Gulf. Acta Micropalaeontologica Sinica, 31(4): 373-386.
Zhou, C. M., Xue, Y. S., 2000. On Polygonal Reticulate Structure of the Ordovician Pagoda Formation of the Western Hunan-Hubei Area. Journal of Stratigraphy, 24(4): 307-309.
Zhou, M. K., Wang, R. Z., Li, Z. M., et al., 1993. Ordovician and Silurian Lithofacies, Paleogeography and Mineralization in South China. Geological Publishing House, Beijing. 55-60.
Zhou, Z. Q., Zhou, Z. Y., 2005. Late Ordovician Trilobite Fauna and Succession, Yichang, Hubei Province, China. Acta Palaeontologica Sinica, 44(3): 327-357.
Zhou, Z. Y., Yuan, W. W., Zhou, Z. Q., 2007. Patterns, Processes and Likely Causes of the Ordovician Trilobite Radiation in South China. Geological Journal, 42(3/4): 297-313. DOI:10.1002/gj.1076