鲁北平原晚第四纪地层结构及沉积演化

以54个浅层新钻孔和多个野外露头为研究对象,综合沉积物粒度、薄片、微体古生物、孢粉、14C测年及静力触探等资料,分析了鲁北平原晚第四纪的地层结构和沉积类型,总结了晚更新世晚期以来的沉积演化。研究表明,末次冰期盛冰期到冰后期,受地势、气候条件控制的黄河河道迁移和海水进退是影响地层结构和沉积特征的主要因素,南北地层结构差异明显,发育古河道、湖沼、黄土、三角洲、潮坪和滨浅海等沉积类型,其中古河道分布面积最广,自下而上可划分为三期。晚更新世晚期至早全新世早期,受干冷气候影响,发育第Ⅰ期古河道,小清河以南沉积黄土层;早全新世晚期至中全新世,气候转暖导致海平面升高,沿海地区形成海侵层和三角洲,内陆地区继承性发育第Ⅱ期古河道和湖沼沉积;中全新世末期或晚全新世以来,受黄河泛滥影响,沉积第Ⅲ期古河道和现代黄河三角洲。地层结构和沉积物分布的研究对于分析地下水位的变化规律,以及选择合适的地震激发层等均有重要的指导意义。

Stratigraphic Structure and Sedimentary Evolution during Late Quaternary in Lubei Plain

Based on 54 new drilled holes in shallow layer and a plurality of outcrops, combined with grain size of sediments, thin sections, microfossils, plant pollen, 14C dating, and static cone penetration test, stratigraphic structures and sedimentary types during late Quaternary in Lubei Plain was studied, and sedimentary evolution after terminal late Pleistocene was summarized. The results showed that, from pleniglacial of the last glacial period to the post glacial period, sea transgression and regression and channel migration of the Yellow River affected by topography and climate change were the main factors influencing shallow stratigraphic structures and sedimentary characters. Differences between the southern and northern stratum structure were obviously. Paleochannels, lakes and marshes, loess, deltas, tidal flats, and littoral-neritic sea developed. The distribution area of paleochannels was largest among them, which were divided into three layers. From terminal late Pleistocene to the early stage of early Holocene, influenced by the dry and cold climate, the first period paleochannels developed, and loess deposited to the south of Xiaoqing River. From the late stage of early Holocene to the middle Holocene, transgression layer and deltas developed in the coastal area, while lakes and marshes and the second period paleochannels developed successively in the inland area. After the last stage of middle Holocene or the late Holocene, influenced by flood of Yellow River, the third period paleochannels and the modern Yellow River delta deposited. The studies of stratigraphic structures and sediments distribution have important guide significance to the analysis on the changes of underground water level and selecting the appropriate seismic excitation layer.