Geological Characteristics of Mud Volcanoes and Diapirs in the Northern Continental Margin of the South China Sea: Implications for the Mechanisms Controlling the Genesis of Fluid Leakage Structures

Table 2

Characteristics of the Yinggehai Basin, Qiongdongnan Basin, Pearl River Mouth Basin, and Southwest Taiwan Basin in the northern South China Sea [43, 57, 65, 67, 76].

	Sediment thickness of Cenozoic	Characteristics of overpressure	The age of the source layers
Yinggehai Basin	The maximum deposition thickness of Tertiary and Quaternary in the central depression exceeds 17000 m.	Overpressure is generally developed in Tertiary, and the pressure coefficient in most areas of the central mud diapir belt is more than 2.0, and the maximum is 2.28.	Neogene Sanya Formation to the bottom of the Yinggehai Formation
Qiongdongnan Basin	The Cenozoic sediment thickness is up to 11000 m. The maximum thickness of Paleogene and Neogene is over 7000 m and 3000~5000 m, respectively.	The overpressure is generally developed in the center of the basin. The pressure coefficient of the central depression in the deep-water area in the south, Ledong-Lingshui sag, and Songnan sag reaches 1.5-2.2, over 2.2, and 2.0, respectively.	Eocene and Oligocene
Pearl River Mouth Basin	The maximum thickness of Cenozoic is over 10000 m, of which the maximum thickness of Paleogene, Neogene, and Quaternary is over 6000 m, 3500 m, and less than 400 m, respectively.	The abnormal overpressure has disappeared in most areas, and only a small overpressure exists in marine mudstone strata below the continental slope and deep source rock strata. The maximum overpressure once possessed by Baiyun sag is only 9.0 MPa.	Eocene and Oligocene
	Dongsha area is characterized by thin (~0.5 km) Cenozoic sediments and thick (up to 5 km) Mesozoic strata.		Mesozoic
Southwest Taiwan Basin	The Cenozoic thickness of the northern depression and southern depression is 5000-7000 m and generally 5000 m, respectively, and the maximum thickness of the sedimentary center near Kaohsiung is more than 10000 m.	Abnormal high temperature and overpressure are develop in the basin.	Miocene and Pliocene

Formation pressure coefficient () = formation pressure ()/hydrostatic pressure (), of YGHB and QDNB refer to [49, 75], respectively.