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Authors requiring further information regarding Elsevier’s archiving and manuscript policies are encouraged to visit: http://www.elsevier.com/copyright Author's personal copy Gondwana Research 19 (2011) 831–849 Contents lists available at ScienceDirect Gondwana Research journal homepage: www.elsevier.com/locate/gr GR Focus Stratigraphy and paleogeography of the Ediacaran Doushantuo Formation (ca. 635–551 Ma) in South China Ganqing Jiang a,⁎, Xiaoying Shi b, Shihong Zhang b, Yue Wang c, Shuhai Xiao d a Department of Geoscience, University of Nevada, Las Vegas, NV 89154-4010, USA b School of Earth Sciences and Resources, China University of Geosciences, Beijing, 100083, China c School of Resources and Environments, Guizhou University, Guiyang, 550003, China d Department of Geosciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA article info abstract Article history: The Ediacaran Doushantuo Formation (ca. 635–551 Ma) in South China contains exceptionally well-preserved Received 1 November 2010 fossils of multicellular eukaryotes including early animals, and it is one of the most intensively investigated Received in revised form 15 January 2011 Ediacaran units in the world. Various stratigraphic methods including litho-, chemo-, bio-, and sequence- Accepted 18 January 2011 stratigraphy have been applied to establish a stratigraphic framework for the Doushantuo Formation, but so far Available online 26 January 2011 regional correlation across the basin relies heavily on two distinctive marker beds, the cap carbonate at the base Handling Editor: M. Santosh and the organic-rich black shale at the top of the Doushantuo Formation. The majority of the Doushantuo Formation in the Yangtze platform was deposited on a rimmed carbonate shelf, with a shelf margin shoal complex Keywords: that restricted the shelf lagoon from the open ocean. Large facies variations are observed in the shallow margins of Ediacaran the shelf lagoon and in the shelf margin-to-slope transition, where depositional environments were near the Doushantuo Formation chemocline of the stratified, anoxic/euxinic shelf lagoon and of the broader Nanhua basin, respectively. Paleogeography Chemocline instability in the shelf lagoon and in the Nanhua basin caused local geochemical cycling, resulting in Early animals significant variations in carbon and sulfur isotopes and in redox-sensitive elemental concentrations. Most benthic Yangtze platform eukaryotic fossils (including animal fossils) of the Doushantuo Formation have been found from the shallow South China margins of the shelf lagoon and from the shelf margin–slope transition, but rarely from deep-water environments that may have been below the chemocline for most of the Doushantuo time, implying the sensitivity of eukaryotes to paleogeographically controlled chemocline fluctuations. © 2011 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved. Contents 1. Introduction ............................................................. 832 2. Development of the Ediacaran Yangtze Platform ............................................ 832 3. Stratigraphy of the Doushantuo Formation ............................................... 834 3.1. Notes on Some Representative Sections ............................................. 834 3.2. Lithostratigraphic Marker Beds ................................................. 836 3.2.1. The Doushantuo Cap Carbonate ............................................. 836 3.2.2. The Organic-Rich Black Shale at the Top of the Doushantuo Formation .......................... 837 3.3. Sequence Stratigraphy ..................................................... 838 3.4. Chemostratigraphy and Biostratigraphy ............................................. 838 4. Paleogeography of the Doushantuo Formation ............................................. 838 4.1. Facies Distribution Across the Shelf-to-Basin Transects ...................................... 838 4.2. Depositional Model and Paleogeographic Reconstruction ..................................... 840 5. Discussion .............................................................. 842 5.1. Paleogeographic Influence on Geochemical Variations ....................................... 842 5.2. Basin Restriction and Phosphorite Deposition ........................................... 844 5.3. Paleogeographic Distribution of the Doushantuo Biotas ...................................... 845 ⁎ Corresponding author. Tel.: +1 702 895 2708; fax: +1 702 895 4064. E-mail address: [email protected] (G. Jiang). 1342-937X/$ – see front matter © 2011 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved. doi:10.1016/j.gr.2011.01.006 Author's personal copy 832 G. Jiang et al. / Gondwana Research 19 (2011) 831–849 6. Conclusion .............................................................. 845 Acknowledgements ............................................................. 847 References ................................................................. 847 1. Introduction et al., 2010), or even by complete isolation of the sedimentary basin (Bristow et al., 2009). Thus a comprehensive sedimentological and The Doushantuo Formation (ca. 635–551 Ma) in South China is paleogeographic framework for the Doushantuo Formation becomes one of the most intensively investigated Ediacaran stratigraphic units critical for future geochemical and paleobiological studies. owing to its exceptionally well-preserved fossil record (Yuan et al., Attempts to establish a stratigraphic and sedimentological frame- 2002; Chen, 2005). A plethora of multicellular fossils including early work for the Doushantuo Formation have been made in numerous animals, exemplified by a few representative biotas (Fig. 1) such as publications (e.g., Wang, 1985; Cao et al., 1989; Liu et al., 1993; Wang the Miaohe biota (Zhu and Chen, 1984; Chen and Xiao, 1992; Xiao et et al., 1998; Jiang et al., 2003a, 2006a, 2006b; Wang and Li, 2003; Zhu al., 2002), Jiulongwan biota (Yin and Liu, 1988; Xiao, 2004; Yin et al., et al., 2003, 2007; Zhou and Xiao, 2007; Vernhet et al., 2006, 2007, 2004, 2007; Zhou et al., 2007; McFadden et al., 2008, 2009), Weng'an 2010), but large uncertainties still exist, especially in aspects related biota (Zhang, 1989; Li et al., 1998; Xiao et al., 1998), Wenghui biota to the degree of basin restriction and the exact paleogeographic (Zhao et al., 2005; Tang et al., 2008; Wang et al., 2008a, 2008b; Zhu location of particular sections. This is largely due to the poor exposure et al., 2008) and Lantian biota (Yan et al., 1992; Yuan et al., 1999, of the Doushantuo Formation and the tectonic complexity in South 2011), have been described from the Doushantuo Formation, China in general. The Doushantuo Formation varies in thickness from providing a rare window for understanding the evolutionary pattern 40 m to 300 m (Zhu et al., 2007) and in cases shows rapid facies of organisms at the dawn of animal life. For the purpose of changes among adjacent sections. Patchy outcrops of the Doushantuo stratigraphic correlation and understanding the causal link between Formation cover the entire Yangtze block for more than biogeochemical events and biotic evolution, intensive geochemical 1,620,000 km2, but complete sequences can only be observed along analyses have also been conducted for the Doushantuo Formation, fresh roadcuts and stream valleys. In addition to these limitations, including carbon, sulfur, and strontium isotopes (e.g., Yang et al., strong weathering and civilian construction can destroy some of the 1999; Shields et al., 2004; Guo et al., 2007; Jiang et al., 2007, 2008; classic sections in a few years so that measurements of the same Zhou and Xiao, 2007; Zhu et al., 2007; McFadden et al., 2008; Ader section by different groups often show large variations in thickness et al., 2009; Zhao et al., 2009; Zhao and Zheng, 2010; Li et al., 2010; and contents. Sawaki et al., 2010) and redox-sensitive elements (Bristow et al., In this paper, we review and summarize some of the representa- 2009; Huang et al., 2009; Li et al., 2010), but in comparison with the tive stratigraphic sections of the Doushantuo Formation and provide a paleontological studies, conclusions are much less definitive. For sedimentological interpretation and paleogeographic reconstruction example, carbon isotope analyses from different sections across the for this unit across the Ediacaran Yangtze platform. Because most of basin show large variations in both absolute δ13C values and the the research on the Doushantuo Formation and the best outcrops of number of negative excursions (Guo et al., 2007; Jiang et al., 2007, this unit are concentrated on the central part of the Yangtze platform 2008; Zhou and Xiao, 2007; Zhu et al., 2007; Ader et al., 2009; Wang in Hubei, Hunan, and Guizhou provinces (Fig. 1B), the discussion will and Shi, 2009). Sulfur isotopes from the inner and outer shelf