Architecture and evolution of deep-water cyclic deposits in the Qiongdongnan Basin, South China Sea: Relationship with the Pleistocene climate events

Cyclic deposit systems, which exhibit mass-transport deposits at the base and channel-levee deposits toward the top, are identified in Pleistocene sequences of the deep-water Qiongdongnan Basin at depths between 1000 and 1500 m. Based on 3D seismic data, seismic amplitude, coherence, time thickness, waveform classification, and stratal slices, we show the vertical evolution of the cyclic deposit system. Channel-levee deposits display the sequence from the erosional channel systems to the leveed channel systems. Erosional channel systems have a stronger ability to incise the slope and contain erosional channels, un-developed levees, smooth lateral margins, crevasse splays, and slides. Leveed channel systems, which are less deeply incised than erosional channel systems, contain leveed channels, developed levees and overbank deposits. Kinematic indicators suggest that cyclic deposit systems are sourced from shelf edge/upper slope systems in central Vietnam, where mountainous rivers deliver high amounts of terrigenous clastics. The proper order of the cyclic deposit system, pollen cycles from Site 1144, and the maximum δ13C values (δ13Cmax) at 1.6, 1.0 and 0.5 Ma from Site 1143 suggest a new model for the systematic deep-water sequences that may be related to the different stages of Pleistocene relative sea-level changes on the long eccentricity cycle time-scale. The start time point of three cyclic deposit systems is inferred respectively corresponding to three climate events at 1.6, 0.9 and 0.4 Ma during the Pleistocene.