叠合断陷盆地沉积体系分析——以东海丽水—椒江凹陷为例

摘要

丽水—椒江凹陷是我国近海海域典型的叠合断陷盆地。综合分析岩芯、地震、录井、测井等资料,对东海丽水—椒江凹陷沉积体系开展了重点研究。分析认为,古新世研究区主要发育5种沉积体系：扇三角洲体系、三角洲体系、湖泊体系、海洋体系及重力流体系。在此基础上对古新统各组的沉积体系展布进行了深入探讨,其中,断陷初期月桂峰组为湖泊沉积环境,而后断陷继续,海侵发生,沉积环境转变为海洋环境;古新统沉积期三角洲体系主要发育于凹陷西缓坡,以闽浙隆起为物源,扇三角洲主要发育于同沉积断裂控制的东侧陡坡带,在月桂峰及灵峰组沉积期,灵峰潜山出露水面,其两侧形成多个扇三角洲（近岸水下扇）沉积。基于以上研究,预测出研究区的两个有利勘探相带：灵峰潜山两侧扇三角洲（近岸水下扇）及滨浅海（湖）砂体、丽水西次凹西斜坡南部与断块有利构造相匹配的三角洲前缘及滑塌重力流砂体。%Lishui-Jiaojiang Sag is the representative offshore superimposed rift-subsidence basin of China.Integrated study of well core,seismic,drilling,and logging shows that there are five sedimentary systems of the Paleocene in Lishui-Jiaojiang Sag： fan delta system,delta system,lake system,system and gravity flow system.The distribution patterns of the depositional systems in space are analyzed as that there was lacustrine environment in the Yueguifeng Formation,and then,strong rifting proceeded,the basin underwent a large-scale transgression,sedimentary environment changed into marine environment,delta system developed in the west gentle slope which was provided by the Minzhe uplift,fan delta system developed in the east steep hill which was controlled by synsedimentary faults.Lingfeng buried hill was out of water surface in the Yueguifeng ang Lingfeng Formation,there deposited several fan delta systems and nearshore subaqueous fan systems in its both sides.Based on the research,two favorable areas are proposed as fan delta（nearshore subaqueous fan） and littoral-shallow sea（lake） sand body on both sides of the Lingfeng buried hill,delta front and slumping gravity flow sand body matching fault block favorable structure in the south of the western slope of West Subsag of Lishui Sag.