Canadian Journal of Earth Sciences Early Telychian (Silurian) marine siliciclastic red beds in the Eastern Yangtze Platform, South China: distribution pattern and controlling factors Journal: Canadian Journal of Earth Sciences Manuscript ID cjes-2015-0209.R1 Manuscript Type: Article Date Submitted by the Author: 20-Jan-2016 Complete List of Authors: Liu, Jianbo; Peking University, Paleontology and Stratigraphy School of Earth and SpaceDraft Sciences Wang, Yi; Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences Zhang, Xiaole; Peking University, Paleontology and Stratigraphy School of Earth and Space Sciences; Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences Jia-yu, Rong; Nanjing Institute of Biology and Palaeontology South China, Eastern Yangtze Platform, early Telychian, red beds, sea Keyword: level, climatic change, Valgu Event https://mc06.manuscriptcentral.com/cjes-pubs Page 1 of 27 Canadian Journal of Earth Sciences 1 Early Telychian (Silurian) marine siliciclastic red beds in the Eastern Yangtze 2 Platform, South China: distribution pattern and controlling factors 3 Jianbo Liu, Yi Wang, Xiaole Zhang 1, and Jiayu Rong 4 1Corresponding author (e-mail: [email protected] ; Tel: +86 132 76641013). 5 6 X.L. Zhang 1 and J.B. Liu. Paleontology and Stratigraphy, School of Earth and 7 Space Sciences, Peking University, Beijing 100871, China 8 X.L. Zhang 1, Y. Wang and J.Y. Rong. State Key Laboratory of Palaeobiology and 9 Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of 10 Sciences,Draft Nanjing 210008, China 11 Jianbo Liu: [email protected]; Yi Wang: [email protected]; 12 jiayu Rong: [email protected] 13 14 15 16 17 18 19 20 21 22 1 https://mc06.manuscriptcentral.com/cjes-pubs Canadian Journal of Earth Sciences Page 2 of 27 1 Abstract: The distribution pattern of early Telychian ( turriculatus-crispus graptolite 2 biozone) red beds in the Eastern Yangtze Platform of South China is reconstructed 3 based on regional geologic data. The red beds are developed in three areas, which are 4 separated by regions without red deposition. The distribution pattern indicates that the 5 Cathaysian Oldland was the provenance of sediment rich in ferric oxides, which are 6 essential for the formation of red beds. Silurian marine siliciclastic red beds, both in 7 China and worldwide, tended to develop during times of relatively low sea level. 8 Coeval hematitic oolites that formed far from the coast may record a change from 9 reducing to oxidizing conditions in the ocean. Furthermore, it is likely that a fall in 10 global sea level, a transition fromDraft reducing to oxidizing conditions in the ocean, and a 11 cooling climate, all of which were closely related to the early Telychian Valgu Event, 12 promoted the global development of marine red beds during this period. 13 14 Keywords: South China, Eastern Yangtze Platform, early Telychian, red beds, 15 sea level, climatic change, Valgu Event 16 17 18 19 20 21 22 2 https://mc06.manuscriptcentral.com/cjes-pubs Page 3 of 27 Canadian Journal of Earth Sciences 1 Introduction 2 Many studies have considered whether red bed deposition can be used as an 3 indicator of climatic and sedimentary conditions (Van Houten 1961; Walker 1967; 4 Dubiel 1994; Retallack 2001). However, most of them have concluded that red color 5 of sediment is not a reliable indicator of climatic conditions (e.g., Sheldon 2005). 6 Meanwhile, red beds are not exclusive in terrestrial environments, but also found in 7 nearshore (e.g., Douglas and Roger 1979), offshore settings (e.g., Ziegler and 8 McKerrow 1975), even deep marine environments (e.g., Wang and Hu 2005), some of 9 which are not in favor of the formation of red deposition, according to traditional 10 perceptions. These findings highlightDraft the difficulty in identifying the controls on color 11 changes—a topic of particular interest in studies of red and black deposition. 12 Consequently, in recent years the nature of red marine strata has received considerable 13 attention (Wang and Hu 2005; Wang et al. 2011; Brett et al. 2012; Rong et al. 2012; 14 Zhang et al. 2014). 15 Marine red beds fall into three categories based primarily on the water depth of 16 deposition (Brett et al. 2012; Rong et al. 2012). Type I red beds are deep oceanic red 17 beds (DORBs) that are directly related to oceanic currents and the distribution of 18 organic carbon/oxygen pools (Wang and Hu 2005; Hu et al. 2006). Type II red beds 19 are deposited in offshore or deep oceanic basin environments (Ziegler and McKerrow 20 1975; Brett et al. 2012; McLaughlin et al. 2012). Type III red beds are deposited in 21 near-shore basins that are characterized by shallow-water sedimentary structures and 22 faunal assemblages (Rong et al. 2012; Zhang et al. 2014). 3 https://mc06.manuscriptcentral.com/cjes-pubs Canadian Journal of Earth Sciences Page 4 of 27 1 Marine red beds are widely distributed in Silurian sedimentary basins in Western 2 Europe, North America, southern and western China (Ziegler and McKerrow 1975; 3 Ettensohn 2008; Rong et al. 2003; Rong et al. 2012), and are characterized by type II 4 and III red beds. The exact ages of individual red beds vary from location to location. 5 However, in general they first appeared near the Aeronian–Telychian boundary and 6 formed widespread deposits in the early Telychian (primarily within the 7 turriculatus-crispus graptolite biozone), the mid Telychian (within the 8 crenulata-spiralis graptolite biozone), and near the Telychian–Wenlock boundary (Mu 9 1962; Ziegler and McKerrow 1975; Loydell 1998; McLaughlin et al. 2012; Rong et al. 10 2012) (Fig. 1). Draft 11 Figure 1 12 Silurian marine red beds developed very well in both the Upper and Lower 13 Yangtze Region, and extend laterally for hundreds of kilometers. They are commonly 14 used for regional stratigraphic correlation given their striking color (Rong et al. 1984). 15 Comprehensive biostratigraphic studies using graptolites (Chen 1984), conodonts 16 (Wang 1998, 2011), and chitinozoans (Geng et al. 1997) have documented red beds 17 occurrence at three distinct horizons: ‘lower red beds’ (LRBs) of early Telychian age, 18 ‘upper red beds’ (URBs) of mid Telychian age, and red beds of Ludlow-Pridoli age 19 (Wang et al. 2010, 2011; Rong et al. 2012). The geological ages of red beds at each 20 horizon fall into short time intervals and each show a clear synchroneity in different 21 locations in South China (Rong et al. 2003; Rong et al. 2012), based on evidences of 22 biostratigraphy, for example, the graptolite zones. 4 https://mc06.manuscriptcentral.com/cjes-pubs Page 5 of 27 Canadian Journal of Earth Sciences 1 These studies of Telychian marine red beds resulted in the publication of several 2 geological maps (Chen and Rong 1996; Rong et al. 2003; Rong et al. 2012) that have 3 subsequently been used to reconstruct the Kwangsian Orogeny in South China (Chen 4 et al. 2014). However, the depositional setting of the South China red beds and the 5 relationships between the red beds and Silurian paleoceanography, paleoclimatology, 6 and tectonics remain poorly known (Rong et al. 2012). 7 In recent years, there has been a remarkable transition towards viewing the 8 Silurian as a highly dynamic period (e.g., Munnecke 2010). Six large positive carbon 9 isotope excursions associated with major extinctions and sea level fluctuations have 10 been recognized (Calner 2008; MunneckeDraft et al. 2010; Cramer et al. 2011); however, 11 our understanding of the nature of these events and their inner correlations remains 12 incomplete. Some relative studies concerning two transitions in sediment color (green 13 to red and gray to black) have aroused much attention in these years (Kiipli 2004; 14 Brett et al. 2012; McLaughlin et al. 2012) and may shed light on these puzzles. The 15 role played by red beds as possible time-specific facies (e.g., Brett et al. 2012) 16 requires more detailed studies before they can be used as an indicator of geological 17 events. 18 Geological setting 19 The distribution pattern and probable controlling factors of early Telychian red 20 beds in the Upper Yangtze Region were talked in detail by Rong et al. (2012). This 21 study focuses on the red beds of early Telychian age (primarily within the 22 turriculatus-crispus graptolite biozone) from the Eastern Yangtze Platform of South 5 https://mc06.manuscriptcentral.com/cjes-pubs Canadian Journal of Earth Sciences Page 6 of 27 1 China (Fig. 2RA). The study area covers the Lower Yangtze region (Anhui, Jiangsu 2 and Jiangxi provinces) and parts of other adjacent regions (Hubei and Zhejiang 3 provinces). It belongs to the South China Block (SCB). The SCB consists of the 4 Yangtze and Cathaysian blocks and were under constant influence of NW-SE 5 compressional stress of the Kwangsian Orogeny (approximately equivalent in age to 6 the Caledonian Orogeny) (Rong et al. 2010; Chen et al. 2014). From the Late 7 Ordovician to the Early Silurian, the Cathaysian Oldland expanded rapidly to the 8 northwest (Rong et al. 2010; Chen et al. 2014). The Nanhua Foreland Basin (NFB) 9 formed and evolved during this time, deposited thousands of meters of sediment (Li 10 1998) before terminated by a finalDraft stage with association of the uplift of the Nanhua 11 Orogenic Belt (NOB). Today, only a remnant basin is recognized due to later geologic 12 modification. The evolutionary history and provenance of the NFB are still under 13 discussions (Yao et al. 2015). However, it appears to have undergone a similar 14 tectonic evolution to other foreland basins of the same age, such as the Appalachian 15 Foreland Basin (AFB) (Su et al.