Abstract:

Based on the integrated analysis of the bathymetric data and high-resolution seismic data, the morphological features and internal structures of the Central Canyon System (CCS) in eastern Qiongdongnan basin (QDNB) have been described and dissected accurately. The result shows that the CCS in eastern QDNB was located in the central part of the Changchang depression with an NEE orientation, showing a narrow, straight course in the plan and symmetrical V-shaped morphology with steep flanks in seismic profiles. The infillings were considered as turbidite channel lag deposits, mass transport complex-sheet sands (MTC-sheet complex) with cake-layer geometry, turbidites, and collapse deposits. They showed a multiple evolutional processes. The distinct differences of the CCS between the western and eastern segments implied that the canyon in eastern QDNB was primarily controlled by the plaeo-morphological feature associated to the tectonic transformation around 11.6 Ma, which might form the axial sub-basin in the central part of Changchang depression seemed as the rudiment of the CCS, define the morphology, and influence the sediment transports and accumulation patterns. The canyon in eastern QDNB wasconsidered as a tectonic-dominated submarine canyon. During the Holocene period, the sufficient deposits could be discharged by the slope canyons at the lower slope, where the modern submarine fan developed. Then the deposits were captured by the head of modern central canyon, and further transported along the canyon from west to east. The three modern sediment transportation models in eastern QDNB, the vertical transportation along the slope from north to south, the veer motion transportation in the head area of modern central canyon dominated by the topography, and the axial transportation associated to the canyon orientation from west to east, would be helpful in understanding the deepwater sedimentary processes in QDNB and provide more evidence for the forming of the CCS.

Key words: central canyon system, internal architecture, tectonic transformation, sediment transportation model, eastern Qiongdongnan basin