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Edinburgh Research Explorer Edinburgh Research Explorer Early Cretaceous palaeogeographic evolution of the Coqen Basin in the Lhasa Terrane, southern Tibetan Plateau Citation for published version: Sun, G, Hu, X & Sinclair, H 2017, 'Early Cretaceous palaeogeographic evolution of the Coqen Basin in the Lhasa Terrane, southern Tibetan Plateau', Palaeogeography, Palaeoclimatology, Palaeoecology. https://doi.org/10.1016/j.palaeo.2017.06.006 Digital Object Identifier (DOI): 10.1016/j.palaeo.2017.06.006 Link: Link to publication record in Edinburgh Research Explorer Document Version: Peer reviewed version Published In: Palaeogeography, Palaeoclimatology, Palaeoecology General rights Copyright for the publications made accessible via the Edinburgh Research Explorer is retained by the author(s) and / or other copyright owners and it is a condition of accessing these publications that users recognise and abide by the legal requirements associated with these rights. Take down policy The University of Edinburgh has made every reasonable effort to ensure that Edinburgh Research Explorer content complies with UK legislation. If you believe that the public display of this file breaches copyright please contact [email protected] providing details, and we will remove access to the work immediately and investigate your claim. Download date: 05. Oct. 2021 PALAEO-08322; No of Pages 18 Palaeogeography, Palaeoclimatology, Palaeoecology xxx (2017) xxx–xxx Contents lists available at ScienceDirect Palaeogeography, Palaeoclimatology, Palaeoecology journal homepage: www.elsevier.com/locate/palaeo Early Cretaceous palaeogeographic evolution of the Coqen Basin in the Lhasa Terrane, southern Tibetan Plateau Gaoyuan Sun a,b,⁎,XiumianHub, Hugh D. Sinclair c a School of Earth Sciences and Engineering, Hohai University, Nanjing 211100, China b State Key Laboratory for Mineral Deposits Research, School of Earth Sciences and Engineering, Nanjing University, Nanjing 210023, China c School of GeoSciences, University of Edinburgh, Drummond Street, Edinburgh EH8 9XP, Scotland, UK article info abstract Article history: The Lower Cretaceous sedimentary strata in the Lhasa Terrane record the palaeogeographic and tectonic history Received 26 March 2017 of the Tibetan Plateau prior to the India-Asia collision. The Lower Cretaceous strata in the Coqen Basin of the Received in revised form 3 June 2017 northern Lhasa subterrane include the Duoni and Langshan Formations. The Duoni Formation is composed of Accepted 11 June 2017 conglomerates, sandstones, siltstones and mudstones in the south deposited in a fluvial environment and quartz- Available online xxxx ose-lithic sandstones, siltstones and mudstones in the north deposited in a shelf-coastal environment. The over- lying Langshan Formation is characterized by abundant Orbitolina- and rudist-bearing wackestones and Keywords: Lower Cretaceous packstones, which were deposited on a low-energy carbonate ramp. The Langshan Formation in the Coqen Palaeogeography Basin was deposited between ~119–115 Ma and ~98 Ma based on its large benthic foraminiferal assemblages. Sedimentology Age constraints based on the interbedded tuff and conformably overlying Langshan Formation indicate that Provenance the Duoni Formation was deposited between ~123 and 115 Ma. Sandstone detrital modal compositions further Detrital zircon indicate that the Duoni Formation was primarily derived from magmatic arc and recycled orogen sources. Detri- tal zircons from the Duoni Formation yield a primary age population of 160–110 Ma (peaking at ~130 Ma), with negative εHf(t)values(−18.7 to −2.7), and additional age ranges of 550–500, 1200–900, and 1600–1500 Ma, thereby indicating that the Zenong volcanic rocks and Palaeozoic sedimentary bedrocks in the northern Lhasa subterrane are the most likely sources. The palaeogeography of the northern Lhasa subterrane can be approxi- mately described in two stages. During the Aptian (~123–115 Ma), with the eruption of the Zenong volcanic rocks, the Duoni Formation accumulated in fluvial and shelf-coastal environments and was sourced from the Zenong volcanic rocks and basement rocks from the southern region of the northern Lhasa subterrane. The en- hanced magmatic activities in the northern Lhasa subterrane may have influenced the Duoni Formation deposi- tion. During the Late Aptian-Early Cenomanian (~115–98 Ma), a north-south transgression occurred, causing the majority of the northern Lhasa region to be dominated by shallow-marine limestones of the Langshan Formation. Crown Copyright © 2017 Published by Elsevier B.V. All rights reserved. 1. Introduction reconstruction of the Lhasa Terrane would help to understand its basin evolution and the southern Asia margin tectonic framework The Lhasa Terrane was the last to accrete onto the southern margin prior to the India-Asia collision. Several published studies have analysed of the Asian plate in the Late Jurassic-Early Cretaceous (Kapp et al., the sedimentology and provenance of the Cretaceous basins on the 2007a; Zhu et al., 2013, 2016); thus, it records the early tectonic history northern Lhasa subterrane (Leier et al., 2007a, 2007b; Zhang et al., of the Tibetan Plateau prior to the India-Asia collision (Dewey et al., 2004, 2011, 2012). However, the Early Cretaceous palaeogeography of 1988; Yin and Harrison, 2000). During the Cretaceous, the Lhasa Terrane the Lhasa Terrane remains under intense debate. For example, was influenced by the Lhasa-Qiangtang collision to the north and sub- Murphy et al. (1997) suggested that the southern Tibetan Plateau duction of the Neo-Tethyan oceanic lithosphere to the south (England (Lhasa Terrane) has been uplifted by approximately 3–4 km since the and Searle, 1986; Murphy et al., 1997; Kapp et al., 2007b; Leier et al., Early Cretaceous due to the Lhasa-Qiangtang collision to the north. 2007a, 2007b). The tectonic evolution of the Lhasa Terrane in the However, Zhang et al. (2004, 2012) inferred that the Lhasa Terrane Early Cretaceous is unknown. An Early Cretaceous palaeogeographic remained at approximately sea level until the Early Cenomanian and that its geography was primarily controlled by the subducted Neo-Te- thyan oceanic lithosphere to the south. ⁎ Corresponding author at: School of Earth Sciences and Engineering, Hohai University, Nanjing 211100, China. The Coqen Basin, which is located in the northern Lhasa subterrane E-mail address: [email protected] (G. Sun). and is bounded by the Gangdese magmatic arc to the south and http://dx.doi.org/10.1016/j.palaeo.2017.06.006 0031-0182/Crown Copyright © 2017 Published by Elsevier B.V. All rights reserved. Please cite this article as: Sun, G., et al., Early Cretaceous palaeogeographic evolution of the Coqen Basin in the Lhasa Terrane, southern Tibetan Plateau, Palaeogeogr. Palaeoclimatol. Palaeoecol. (2017), http://dx.doi.org/10.1016/j.palaeo.2017.06.006 2 G. Sun et al. / Palaeogeography, Palaeoclimatology, Palaeoecology xxx (2017) xxx–xxx Bangong-Nujiang suture to the north, is an ideal site to document the components of the Gangdese magmatic arc (Chu et al., 2006; Mo et al., Early Cretaceous history of this region. The Lower Cretaceous deposits 2007, 2008; Wen et al., 2008; Ji et al., 2009; Lee et al., 2009; Zhu et al., in the Coqen Basin include the Duoni Formation clastic rocks and 2011a, 2015), which is related to the northward subduction of Neo-Te- Langshan Formation limestones. To test the palaeogeographic evolution thyan oceanic lithosphere beneath the Lhasa Terrane and the subse- of the Lhasa Terrane, this study presents new data on the sedimentolo- quent India-Asia collision (Yin and Harrison, 2000; Ding et al., 2003; Ji gy, stratigraphy, and detrital zircon geochronology of the Lower Creta- et al., 2009). The Xigaze forearc basin, which is located on the southern ceous strata in the Coqen Basin. These new results, combined with margin of the Gangdese magmatic arc, is characterized by thick se- previously published data, provide new information to build a chrono- quences of Albian–Campanian deep-water turbidites followed by Cam- stratigraphic framework of the Lhasa Terrane during the Early Creta- panian-Maastrichitian shallow-water deposits (Dürr, 1996; Wang and ceous and to detect the sedimentary sources of the clastic rocks, Liu, 1999; Wang et al., 2012; An et al., 2014; Orme et al., 2014; Orme thereby allowing its palaeogeography to be reconstructed. We believe and Laskowaki, 2016). The Gangdese magmatic arc was a significant that relative to the other sedimentary basins on the Lhasa Terrane, the sediment source for the Xigaze forearc basin, in addition to the northern magmatic activities and north-south transgression had significant influ- Lhasa subterrane that also sourced detritus materials (Wu et al., 2010; ences on the Early Cretaceous deposition. An et al., 2014). In the northern Lhasa subterrane, there are widespread Cretaceous 2. Geological setting magmatic rocks that are characterized as the Zenong volcanic rocks (Zhu et al., 2008, 2009, 2011a). Successions of Carboniferous The Tibetan Plateau comprises, from north to south, the Songpan- metasedimentary rocks, Permian limestone, and Jurassic siliciclastic Ganzi complex, the Qiangtang Terrane, and the Lhasa Terrane, which rocks are exposed in the northern Lhasa subterrane (Leeder et al., are separated by the Jinsa and Bangong-Nujiang sutures (Fig. 1A, Yin 1988; Yin et al., 1988). Thick Cretaceous strata are also preserved in and Harrison, 2000). The Lhasa Terrane is separated from the Tethyan the sedimentary basins in the northern Lhasa subterrane;
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