179 / 2022-02-28 11:47:42

The characteristics of terrigenous deep water channel in Zhongjian area

Zhongjian area; Terrigenous; Deep water channel; sea level；Channelized lobe

     The  Zhongjian area  is located in the northern part of the South China Sea The submarine topography in the area is complicated, with islands and valleys distributed alternately, and the water depth reaches 1000-3000m. Since Miocene, zhongjian  area has been in a period of stable subsidence, with no active tectonic activities, and continental slope deep-water sedimentary environment after the Middle Miocene.

     During the sedimentary period of huangliu Formation in upper Miocene, the deep-water channel deposits in the study area can be divided into three periods, which are controlled by the rise and fall of relative sea level, and are in the early stage of low-transgression and gradually disappear with the rise of sea level. The early stage of the channel is the low level stage, and the channel is U/V downcut channel with strong restriction. The upstream channel is multiple independent channels, and the downstream channel converges into a compound channel and cuts each other. In the middle stage of the channel, the sea level rises rapidly, which is characterized by the channel complex with strong restrictions. The upstream of the channel is composed of multiple restricted channels, and the downstream is composed of multiple independent channels that converge into a channel complex and migrate and swing in the plane. The late stage of the channel is the highest stage of sea level in transgressive period, which is characterized by channel-lobes with weak restriction. In this stage, the upstream of channel is a single swinging channel, the middle is a channel complex composed of several swinging channels, and the downstream is channelized lobes.

      The three stages of deep water channel developed in huangliu Formation in western Huaguang Sag of Qiongdongnan Basin are controlled by the change of sea level and show different characteristics. From early channel to late channel is a process of from low - early transgression sea level , the restrictive of the channel is weaker and weaker, from early restrictive of single channel to multiple channel interaction cutting and migration channel complex, then transition to the late composite channel and channelized lobes, and generally retrogradated to land.