ORIGINAL RESEARCH PAPER Geophysical evidence for cyclic sediment deposition on the southern slope of Qiongdongnan Basin, South China Sea Qi-Liang Sun • Shi-Guo Wu • Thomas Lu ¨dmann • Bin Wang • Tao-Tao Yang Received: 20 December 2010 / Accepted: 11 March 2011 / Published online: 26 March 2011 Ó Springer Science+Business Media B.V. 2011 Abstract Gravity flow deposits form a significant com- ponent of the stratigraphic record in ancient and modern deep-water basins worldwide. Analyses of high-resolution 3D seismic reflection data in a predominantly slope setting, the southern slope of Qiongdongnan Basin, South China Sea, reveal the extensive presence of gravity flow deposi- tional elements in the Late Pliocene–Quaternary strata. Three key elements were observed: (1) mass transport deposits (MTDs) including slumps and debris flows, (2) turbidity current deposits including distributary channel complexes, leveed channel complexes and avulsion chan- nel complexes, and (3) deep-water drapes (highstand con- densed sections). Each depositional element displays a unique seismic expression and internal structures in seis- mic profiles and attribute maps. Based on seismic charac- teristics, the studied succession is subdivided into six units in which three depositional cycles are identified. Each cycle exhibits MTDs (slump or debris) at the base, overlain by turbidities or a deep-water drape. The genesis of these cycles is mainly controlled by frequent sea-level fluctua- tions and high sedimentation rates in the Late Pliocene– Quaternary. Moreover, tectonics, differential subsidence, and paleo-seafloor morphology may have also contributed to their formation processes. The present study is aimed to a better understanding of deep-water depositional systems, and to a successful hydrocarbon exploration and engi- neering-risk assessment. Keywords Deep-water sedimentation Á Cyclic deposition Á Mass transport deposits Á Turbidite Á Sea level change Á Qiongdongnan Basin Introduction The understanding of deep-water depositional systems has advanced significantly in recent years (Posamentier and Kolla 2003). As exploration has focused on deep-water areas, more and more multi-channel high resolution 2D and 3D seismic data were acquired in deep-water settings (e.g., Beaubouef and Friedmann 2000; Posamentier et al. 2000; Posamentier and Kolla 2003; Yuan et al. 2009). The 3D seismic data afford an excellent view of the deep-water depositional environment, in some instances with vertical resolution down to 2–3 m (Posamentier and Kolla 2003). Gravity-induced across-slope sedimentation processes, such as slides, slumps, debris flows, and turbidity currents, are important and predominant on continental slope domains (Yuan et al. 2009). Through compiling from Dott (1963), Nardin et al. (1979), Posamentier and Kolla (2003), Moscardelli et al. (2006), Moscardelli and Wood (2007) and Bull et al. (2009), the terminologies used here and their seismic reflection characteristics are as follows: (1) slide is defined as shear failure along discrete shear planes without Q.-L. Sun (&) Á S.-G. Wu Key Laboratory of Marine Geology and Environment, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China e-mail: sunqiliang@qdio.ac.cn Q.-L. Sun Graduate University of Chinese Academy of Sciences, Beijing 100049, China T. Lu ¨dmann Centre of Marine and Atmospheric Sciences, University of Hamburg, Hamburg, Germany B. Wang Á T.-T. Yang PetroChina Hangzhou Institute of Geology, Hangzhou 310023, China 123 Mar Geophys Res (2011) 32:415–428 DOI 10.1007/s11001-011-9121-5