东海盆地西南部正的反转构造

POSITIVE INVERTED STRUCTURES IN SOUTHWEST OF THE EAST CHINA SEA BASIN

王国纯

Wang Guochun

东海盆地西南部地质特征与盆地中、北部有很大的差异:前者前上第三系为海相沉积环境,其断裂为雁行展布,始新世末期的区域抬升长达15—20×10a。文中首次提出该区存在正的反转构造,并对其形成机制进行了分析。正的反转构造下伏高压泥岩是有利的生油岩系,预测东海盆地西南部正的反转构造分布区为有利的含油气区。

Geological characteristics in southwest of the East China Sea Basindiffer greatly from those of other parts:1.It was marine environment before the Neogene;2.The faults are distributed in echelon pattern;3.Regional uplift in the end of the Eocene resulted in sedimental lacunaeand erosion for about 15-20 million years in the west part of the area.This article firstly proposed the existance of positive inverted struc-tures.The main proofs are:1.There is a“basin”shape basement beneath the positive invertedstructures;2.Seismic reflection is“dune”shape;3.Sediments of great thickness spread under the structures;4.The fault texture on top of the structures is “flower”shape;5.The faults usually do not cut the basement;6.The upper parts of the structures are generally eroded;7.Formations beneath the structures have abnormal high-pressure;8.Low vilocity.The existance of wrench faults,plastic formations,seesaw motion andhorizontal compression are considered to be the formation factors of thiskind of structures.It has been proved by well drilling in both Bohai and the South ChinaSea that high-pressure mudstones beneath the structures are the most favour-able source rocks.Thus,the structures under which there are plasticformations are favourable places for the enrichment of hydrocarbon in the East China Sea Basin.

10.11743/ogg19890206