Sedimentary characteristics and origin of moundes in Meishan Formation, southern Qiongdongnan Basin

Abstract

While the Meishan Formation, southern Qiongdongnan Basin, has been widely discussed because of their unique mound-like reflection characteristics, there is still considerable controversy on the origin of those mounds. This study is based on a large number of 2D seismic data and high-resolution 3D seismic data in the Qiongdongnan Basin, combined with deep-water drillings, elucidates the mound-like reflection characteristics and discusses the origin of the Meishan Formation integrated among seismic facies characteristics, sediment source, transport channels, paleo-geomophic, sea level changes, and tectonic activity. The results show that during Middle Miocene, due to forced retreat, the sea level dropped to a lower level throughout the Qiongdongnan Basin, and the southern uplift was partially exposed and denudated provided a large number of sediments. During the Late Miocene, the regional tectonic activities caused the gravity instability in the southern uplift, and the sediments were transported to the basin center in terms of the turbidite channels. Subsequently, the mound-like reflection features at the top of the Meishan formation in the Qiongdongnan Basin were caused by turbidity erosion which provenance was provided by the sediments from the southern uplift. The further discussions on the origin of the mounds are not only helpful to better understand the formation of mound-like deposits, but also illustrate that the composition of those mound-like deposits is clastic sediments rather than reefs, which has great value for deep-water hydrocarbon reservoirs in the Qiongdongan Basin.

Keywords

• qiongdongnan basin
• meishan formation
• submarine channels
• southern uplift
• mounds