The "butterfly delta" system of Qiongzhou Strait: Morphology, seismic stratigraphy and sedimentation.

Analysis of high resolution sub-bottom profiles, topographical data and sediment samples reveals that the tidal delta system of Qiongzhou Strait is morphologically a "butterfly delta" system consisting of Western Mouth Tidal Delta (WMTD) and Eastern Mouth Tidal Delta (EMTD). WMTD covers an area of about 11,000 km², and is more than two times larger than EMTD (4000 km²). WMTD is fan-shaped with a tributary branch extending southwards along Hainan Island, while EMTD is typically fan-shaped. Seismic architectures of WMTD and EMTD are both characterized by a thick progradational unit overlying a thin transgression unit. Both WMTD and EMTD start to develop at about 8.7 cal ka BP when Qiongzhou Strait completely opened, and have the same three sedimentary facies: tidal delta top, tidal delta slope and tidal delta toe. The formation of WMTD and EMTD is attributed to Qiongzhou Strait's hydrodynamic regime which is dominated by the strong east-west reciprocal-tidal currents and influenced by the year-round westward mean flow modified by the wind-driven seasonal currents. [ABSTRACT FROM AUTHOR]