渤海莱州湾第四纪晚期介形类特征及海侵变化研究

发布时间：2018-11-26 12:45

【摘要】：渤海湾地区晚更新世以来共经历了 9次海岸线变化事件,发育有三套海相地层。分别是全新世形的第Ⅰ海相地层,在晚更新世形的第Ⅱ、第Ⅲ海相地层。莱州湾作为渤海三大海湾之一,其第四纪晚期海相地层研究主要集中在黄河三角洲流域和莱州湾的东、南岸,针对莱州湾西南岸海侵的研究相比之下较少。本课题通过分析研究区介形类化石属种特征、分布特征,对莱州湾西南岸第四纪晚期发育的海侵地层进行识别,利用同位素测年法对海侵事件发生的时代进行确定,并对海侵最盛时期的影响范围进行推断。本次研究共采集莱州湾西南岸GK138、GK111、GK95、GK89、GK79、GK74、GK59七个钻孔的448个样品。采用热酸法对样品进行处理,并在显微镜下对每个样品进行筛选,共发现含介形类化石样品227个,包含22个属31个种,其中海相类的适宜直微花介Cathatocytheretta apta、网纹豆艳花介Leguminocythreis reticulata,广盐类的美山双角花介Bicornucythere bisanensis、眼点湾贝介Loxoconcha ocellata、压印中华美花介Sinocytyeridea impressa等在数量和分布规模上占有绝对优势;陆相类的纯净小玻璃介Candoniella albicans、布氏土星介Ilyocypris bradyi、粗糙土星介Ilyocypris salebrosa相对较少,分布较为集中。通过研究介形虫属种类型以及群落的分布特征,在本研究区内共识别出晚更新世M3海侵层、晚更新世M2海侵层和全新世M1海侵层。通过AMS14C和OSL测年法对部分样品分析,将三套海相地层分别与全球海平面变化的MIS7阶段、MIS5阶段和MIS1阶段对应,晚更新世的MIS7阶段全球气温上升,冰川消融海平面最高时仅低于现代海平面1Om,莱州湾地区在该时期发生的海侵影响规模最小,仅抵达潍坊侯镇附近;末间冰期MIS5阶段,气温回暖,全球海平面上升至略高于现代海平面,此阶段海侵强度大,沉积较厚,海侵最盛时期海水涌入莱州湾到达广饶县;全新世时期,末次冰期结束,气候温度回升,海平面上升,造就了现代渤海,并形成MIS1阶段海相地层,此阶段海侵最盛时期的海岸线到达龙池镇附近并向纯化方向延伸。而渤海湾其它地区发现的MIS3阶段海侵地层在本研究区内以过渡相沉积环境为主。
[Abstract]:Since the late Pleistocene, the Bohai Bay area has experienced 9 shoreline changes and developed three sets of marine strata. They are the first marine strata of Holocene and the second and third marine strata of late Pleistocene. Laizhou Bay is one of the three major coasts in the Bohai Sea. Its late Quaternary marine stratigraphic studies are mainly concentrated in the Yellow River Delta basin and the eastern and southern shores of the Laizhou Bay, but there are few studies on the transgression of the southwest coast of the Laizhou Bay. In this paper, the transgressive strata developed in the late Quaternary period along the southwest coast of Laizhou Bay were identified by analyzing the characteristics and distribution characteristics of the genus and species of ostracites in the study area, and the epoch of transgressive events was determined by isotopic dating. At the same time, the influence range of transgression was inferred. A total of 448 samples were collected from seven GK138,GK111,GK95,GK89,GK79,GK74,GK59 boreholes in the southwest coast of Laizhou Bay. The samples were treated by thermal acid method, and each sample was screened under microscope. A total of 227 samples containing ostracods were found, including 31 species belonging to 22 genera. Among them, marine species are suitable for direct micro-flower mesopodium Cathatocytheretta apta, mesophyllum Leguminocythreis reticulata,. The quantity and distribution of Sinocytyeridea impressa in the Loxoconcha ocellata, imprint of Bicornucythere bisanensis, in the wide salt species of Mi-shan bigophylla were superior in quantity and distribution scale, and the results showed that the number and distribution of Sinocytyeridea impressa were more and more important in the process of Loxoconcha ocellata, imprint. Candoniella albicans, 's Saturn medium Ilyocypris bradyi, rough Saturn medium Ilyocypris salebrosa is relatively few and the distribution is relatively concentrated. By studying the species types and community distribution characteristics of ostracia, the M _ 3 transgression layer, M _ 2 transgression layer and M _ 1 transgressive layer of Holocene were identified in this study area. Through the analysis of some samples by AMS14C and OSL dating, the three sets of marine strata are corresponding to the MIS7 stage, MIS5 stage and MIS1 stage of the global sea level change, respectively, and the global temperature rise in the MIS7 stage of the late Pleistocene. The maximum melting sea level is only 1Omm lower than that of modern sea level, and the scale of transgression in Laizhou Bay is the smallest, only reaching near Houzhen of Weifang. In the MIS5 stage of the late interglacial period, the temperature warmed and the global sea level rose to a little higher than the modern sea level. At this stage, the transgression intensity was large and the sediment was thicker. The sea water poured into the Laizhou Bay to reach Guangrao County at the peak of the transgression. In the Holocene, the end of the last glacial period, the rise of climate temperature and the rise of sea level formed the modern Bohai Sea and formed the marine strata in the MIS1 stage. The coastline of the transgressive peak period reached near Longchi Town and extended to the direction of purification. The transgressive strata of MIS3 stage found in other areas of Bohai Bay are mainly transitional sedimentary environment in this study area.
【学位授予单位】：山东科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：Q915;P736.22

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