辽东湾晚第四纪以来沉积环境演化

发布时间：2018-03-03 10:03

本文选题：辽东湾　切入点：晚第四纪　出处：《中国海洋大学》2015年硕士论文　论文类型：学位论文

【摘要】：辽东湾地处渤海北部,属于半封闭海湾,是典型的陆架浅海。晚第四纪以来渤海历经海陆的变化,形成了海相和陆相沉积物交替出现的地层。沉积地层中包含海平面变化、沉积环境演化、入海沉积物和气候变化等丰富信息。以沉积地层为研究对象,可以恢复沉积环境和沉积过程,进而了解现代沉积环境的演变方向及趋势。本文根据在辽东湾海区最新获得的3255km的高分辨率浅地层剖面数据和LDD-7孔地质浅钻的粒度、矿物、微体古生物以及测年等资料,运用层序地层学的方法,对该区晚第四纪以来的沉积地层结构进行了精细划分,并对沉积特征和环境演化进行了初步研究。在该地区浅地层剖面上可识别出3个地震单元：SU1、SU2和SU3,其中SU2单元分为SU2-1和SU2-2两个亚层。通过与已有钻孔LD01(水深14m)和C05(水深30m)进行比对分析,结果表明SU1单元为全新世海相沉积层,形成于MIS1；SU2单元为更新世陆相沉积层,形成于MIS2; SU3单元为更新世海相沉积层,形成于MIS3。LDD7孔位于辽东湾中部,取样水深30.5m,钻探进尺50.1m。根据钻孔岩性、沉积构造、AMS 14C年龄和微体古生物组合特征,并与浅地层剖面对比,将LDD7孔划分为4个沉积单元,从上到下依次命名为U1、U2、U3和U4,包括2个海相层和2个陆相层。其沉积环境的变化分别发生于MIS1、MIS2、MIS3和MIS4。其中U3可进一步细分为U3-1、U3-2、U3-3、U3-4四个亚单元层。通过对浅地层剖面和钻孔岩心的分析,恢复了辽东湾晚更新世以来的沉积环境。晚更新世进入末次冰期以来(MIS4),研究区受全球气候冷暖交替变化和海平面升降的影响,先后发生了献县海侵和黄骅海侵,分别沉积了U3海相层和U1海相层。综合分析表明,辽东湾自晚更新世以来沉积环境经历了河湖相-海陆交互相-湖泊相／河漫滩-浅海相的沉积演化过程。
[Abstract]:The Liaodong Bay is located in the northern part of the Bohai Sea and belongs to the semi-enclosed bay, which is a typical continental shelf shallow sea. Since the late Quaternary, the Bohai Sea has undergone sea and land changes, resulting in the formation of marine facies and continental sediments alternately. The sedimentary strata contain sea level changes. Sedimentary environment evolution, sea sediment and climate change are abundant information. Taking sedimentary strata as the research object, the sedimentary environment and sedimentary process can be restored. Based on the new data of 3255km high resolution shallow stratum profile obtained in the Liaodong Bay area and the data of grain size, mineral, micropaleontology and dating of LDD-7 hole geological shallow drilling, etc. Using the method of sequence stratigraphy, the sedimentary stratigraphic structure since the late Quaternary in this area has been classified in detail. The sedimentary characteristics and environmental evolution were preliminarily studied. Three seismic units:: Su _ 1 / U _ 2 and S _ 3 can be identified on the shallow stratigraphic profile of the area, in which the SU2 unit is divided into two sublayers, SU2-1 and SU2-2. LD01 (water depth 14m) and C05 (water depth) are obtained from existing boreholes. The water depth is 30m. The results show that the SU1 unit is the Holocene marine sedimentary layer, formed in the Pleistocene continental sedimentary layer and the SU3 unit is the Pleistocene marine sedimentary layer, and the MIS3.LDD7 pore is located in the middle of Liaodong Bay. The sampling water depth is 30.5 m and the drilling scale is 50.1 m.According to the lithology of the borehole, the age of sedimentary structure AMS14C and the characteristics of micropaleontological assemblage, the LDD7 pore is divided into four sedimentary units in contrast with the shallow formation profile. From top to bottom, they are named U1C U2U3 and U4, including two marine strata and two continental strata. The changes of sedimentary environment occur in MIS1 / MIS2 / MIS3 and MIS4 respectively. U3 can be further subdivided into four subunit layers, U3-1, U3-2, U3-3, U3-4. Through the analysis of shallow strata profile and drilled core, the sedimentary environment of U3 can be further subdivided into four sub-layers of U3-1, U3-2, U3-3, U3-3 and U3-4, respectively. The sedimentary environment since the late Pleistocene in the Liaodong Bay was restored. Since the late Pleistocene entered the last glacial period, the study area was affected by the alternating global climate and the sea level rise and fall, resulting in successively Xianxian transgression and Huanghua transgression. U _ 3 and U _ 1 marine beds were deposited, respectively. The comprehensive analysis shows that the sedimentary environment of Liaodong Bay has undergone a sedimentary evolution process since late Pleistocene, between lacustrine facies, sea and land cross facies, lacustrine facies, floodplain facies and shallow sea facies.
【学位授予单位】：中国海洋大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P736.2

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