Mesozoic sedimentary basin development and tectonic implication, northern Yangtze Block, eastern China: record of continent – continent collision Shaofeng Liu a, * , Ronald Steel b,1 , Guowei Zhang c a Faculty of Geosciences and Resources, China University of Geosciences, Beijing 100083, China b Department of Geology and Geophysics, University of Wyoming, Laramie, WY 82071, USA c Department of Geology, Northwest University, Xi’an 710069, China Received 2 June 2003; revised 10 December 2003; accepted 16 January 2004 Abstract A Mesozoic foreland-basin complex formed along the northern Yangtze plate during subduction of this plate under the Qinling – Dabieshan orogenic belt along the Mianlue suture. As the Yangtze plate moved northwestwards and was obliquely subducted under the Qinling – Dabieshan (Middle – Late Triassic), a flysch foredeep developed in the Diebu – Songpan in the western part of the northern Yangtze plate. During the Late Triassic, a nonmarine molasse basin first formed in the eastern part of the northern Yangtze plate in response to initial collision there. This molasse clastic wedge prograded over the former marine basin and was accompanied by a change from high-sinuosity river systems flowing into basinal lakes, to higher gradient braidplains. Complete oceanic closure along the Mianlue suture during the Middle Jurassic produced a more extensive east – west molasse basin with rivers, deltas and lakes. During Late Jurassic through Early Cretaceous, the depocenter of the nonmarine molasse basin migrated continually from east to west because of intracontinental deformation associated with clockwise rotation of the Yangtze plate relative to the North China plate. In this time interval, the basin was again dominated by fluvial and lake-delta deposition and rivers continued to disperse sediments southwards into the basin. q 2004 Elsevier Ltd. All rights reserved. Keywords: Foreland basin; Sedimentation; Tectonic implication; Northern Yangtze plate 1. Introduction The Qinling–Dabieshan orogenic belt, a major tectonic feature in central China, underwent two major suturing events, and generated two main suture belts during Mesozoic time. These two belts, referred to as the Shangdan and Mianlue belts, are exposed in northern Qinling–Dabieshan along the Xinyang–Shucheng fault (XSF) and in southern Qinling– Dabieshan along the Xiangfan–Guangji fault (XGF) (Fig. 1). The major continental fragments that make up central China—from north to south the North China plate, Qinling– Dabieshan microplate, and Yangtze plate—owe their origins to two episodes of rifting during late Precambrian and Devonian time (Liu and Zhang, 1999; Zhang et al., 2001). The Shangdan and Mianlue oceans separated these crustal fragments from north to south. Closure of the Shangdan ocean led to continent–continent collision between the North China plate and Qinling–Dabieshan plates beginning in late Paleozoic time (Zhang et al., 2001). The development and extension of the Mianlue ocean during the Late Paleozoic and the Early Triassic have been documented by Li and Sun (1996); Li et al. (1996); Lai et al. (1997, 1998); Xu et al. (1998); Liu and Zhang (1999); Dong et al. (1999); Meng and Zhang (1999, 2000); Zhang et al. (2001). With the Permian and Early Triassic subduction and consumption of the Shangdan oceanic basin, the northern margin of the Yangtze plate extended along the Mianlue suture, and was completely separated by this suture from the Qinling–Dabieshan plate to the north. The ophiolites representing the remnants of the palaeo-oceanic crust crop out in the Mianxian-Lueyang and Suixian regions (Li et al., 1996; Lai et al., 1997, 1998; 1367-9120/$ - see front matter q 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.jseaes.2004.01.010 Journal of Asian Earth Sciences 25 (2005) 9–27 www.elsevier.com/locate/jaes 1 Present address: Department of Geological Sciences, The University of Texas at Austin, Austin, TX 78712, USA. * Corresponding author. Tel.: þ86-10-8232-3274; fax: þ 86-10-8232- 1620. E-mail addresses: shaofeng@cugb.edu.cn (S. Liu), rsteel@mail.utexas. edu (R. Steel).