Analysis of Quaternary Mass Transport Deposits Based on Seismic Data in Southern Deep-Water Region of Qiongdongnan Basin, South China Sea

Abstract

Mass transport deposits (MTDs) were identified in Quaternary sedimentary sequences of the southern deep-water (water depth 1,000–1,500 m) region of the Qiongdongnan Basin, South China Sea. Based on high resolution 3D seismic data, seismic amplitude and coherence data are obtained and used to analyse MTDs. Through the seismic profile, two-way-travel time (TWT) time map, time thickness and time slice of target strata, profile characteristics and internal structure of MTDs are revealed. MTDs are characterized of mounded, hummocky, chaotic, low amplitude and discontinuous seismic reflection. MTD-internal thrusts and basal groove marks indicate mass-transport direction from WSW to ENE, suggesting MTD source in the shelf edge/upper slope system offshore central Vietnam, where mountainous rivers deliver high amount of terrigenous clastics. Since about 0.78–1.8 Ma, three depositional cycles characterized by basal MTDs overlain by turbidite channel levee systems have been emplaced in the study area. Timing and source of MTDs suggest a causal link between Quaternary high sedimentation rate to the shelf/upper slope in the Western South China Sea influenced by the eccentricity scale sea-level change and the emplacement of MTDs.