中更新世末期以来黄渤海陆架区衍生沉积体的研究

IOCAS-IR > 海洋环流与波动重点实验室

	中更新世末期以来黄渤海陆架区衍生沉积体的研究
	韩德亮
学位类型	博士
	1999
学位授予单位	中国科学院海洋研究所
学位授予地点	中国科学院海洋研究所
学位专业	海洋地质学
关键词	中更新世末期黄、渤海陆架衍生沉积近源沉积古冬季风
摘要	大量的钻孔及浅地层部面分析资料已经证实，最后冰期时期陆架上的古季风活动得到了加强，风力搬运作用是陆架上的主要外营力，长期而又稳定的干冷季风使海退后的陆架上的海相地层发生解体，出现了沙漠环境，其范围要占据黄、渤海和东海的大部分地区，并在其下风头形成衍生沉积－黄土。晚更新世末期，强劲古季风活动的结果，在中国西部形成沙漠——黄土堆积群（黄土高原及其以西的沙漠区），当它到达陆架区以后，风蚀作用继续存在，会产生同样的地质效果，因而在中国东部陆架区，形成两个新的沙漠－黄土堆积群。其一为渤海沙漠－黄土堆积群，包括渤海海底、渤海海岸一带的古沙漠活动区和辽东半岛西岸、庙岛群岛以及山东蓬莱以西的含有孔虫的黄土沉积。其二为黄海沙漠－黄土堆积群，包括苏北浅滩和长江三角洲地区全新世以前的沙漠活动区和南京一带的下蜀黄土。当冰期逐渐结束，气候转暖，冬季风逐渐减弱之际，南黄海及长江三角洲一带的沙漠范围也相应地缩小，黄土分布的位置也随之缩小。这样在原先的沙漠活动区变成了黄土分布区，也就是所谓硬粘土沉积区。随着古季风活动的进一步衰退和海面的不断升高，来自陆架区的东北风不再是干冷的气流，而是湿度逐渐增大的冷湿气流。在这种环境背景下，长江三角洲地区和陆架上出现有于沼泽发育的环境，所以在全新世海侵的前夕往往形成薄层泥炭沉积。从距今18000年的最后冰期最盛时期到距今10000年开始的全新世海侵，全球气候发生过急剧的变化。位于亚洲东部的古季风活动也经历了盛衰变化。陆架区晚更新世末期以来的地中出现沙层、硬粘土和泥炭层的沉积序列，即“三元沉积结构”，是古冬季风盛衰过程的最好记录。黄河的贯通与青藏高原隆起密切相关，黄河不可能在海拔较高的源头出现之前就已存在。冰期海退时期的陆架不存在类似现在的黄河。现代长江口以北地区在最后冰期时期，为非常恶劣的自然环境，部分地区为冻土带分布区、部分地区为古沙漠活动区。从距今12000年开始，全球气候转暖，大陆冰川逐渐消失，山地冰川后退，洋面升高，在这一过程中黄河得到较多的水量，贯穿成现代的河流系统。而后，随着海面的进一步升高，黄河三角洲不断向西迁移，而进入历史时期。在莱州湾E孔的研究中，我们发现不同时期沉积物中地球化学特征有明显差别。沉积物粒度变化与气候变化密切相关，间冰期主要以砂质沉积为主；冰期以粉砂沉积为主。但晚更新世末期时，在强烈的古冬季风作用下，发生陆架沙漠化，也沉积了一层砂质沉积。衍生沉积的成因的核心是近源沉积。黄渤海陆架衍生沉积中普遍含有孔虫、放射虫、海绿石和粒度组成较粗，大多数都属于近源沉积，真正能随高空气流进行洲际输送黄土物质，是一些非常细粒的尘埃。中更新世期间，苏北宿迁一带的第三纪紫红一红色粘土就已经出露地表，并经常受到风暴的侵蚀。当紫红一红色粘土被搬运到丘陵一带，就形成了下蜀土沉积；当它落在长江三角洲地区的湖相环境时，就形成了岩芯中所见到的杂色粘土。所以下蜀土地属于近源沉积。
其他摘要	It is verified from a lot of core data and shallow layer profiler records that the monsoon activity had been strengthened in the last Glacial period, the transit of the wind was the major exogenic force on the shelf region. Under the long-term and steady dry-cold monsoon, the disintegration of integrated marine stratum occurred and the desert environment appeared on the shelf after regression, which covered the Yellow Sea, the Bohai Sea and most of the East China Sea and the derivative deposits (loess sediment) came into being on the leeward side. During the last stage of Late Pleistocene, under the prevailing paleo-winter monsoon action, the desert-loess sedimental group was formed in the western China (loess plateau and the desert region to the west of the loess plateau). When the paleo-winter monsoon went to the shelf areas, the aeolian erosion kept acting and made the same geological results, two new desert-loess sedimental groups were formed in the eastern China shelf region. One is the Bohai Sea desert-loess sedimental group, inclusion of the paleo-desert area along the seafloor and coastal zone of Bohai Sea and loess contained foraminifera in the west coastal zone of Liaodong islands, Miaodao islands, western region of Penglai city, Shandong province; the other is the Yellow Sea desert-loess sedimental group, inclusion of desert area before Holocene transgression in the North Jiangsu Shoal and Yangtze River delta regions and Xiashu loess near by the Nanjing city. When the glacial epoch ended, the weather came to be warm, the winter monsoon got weaker and weaker, the extension of the desert along the Southern Yellow Sea and the Changjiang River delta reduced and the range of the loess reduced as well. Therefore, the region of the desert activity changed to loess activity, which is also called hard-clay. With the father decline of the paleo-monsoon and the rise of the sea surface, the east-north wind from the shelf was not dry-cold air stream, but the cold-wet air stream whose humidity rise gradually. Under this background, the environment which was propitious to the growth of swamp appeared in the shelf region and the Changjiang River delta, the thin peat sediment was often seen before the Holocene transgression. From the LGM (18Ka BP) to the Holocene transgression (10ka BP), great changes had taken place in world climate, including the paleo-monsoon activity which located in the Eastern Asia. The sedimental series of sand layer, hard-clay and peat in the shelf region since the late stage of Upper Pleistocene, it is so called "three-dimension sedimental constructure", is the best records which the paleo-winter monsoon has prospered and declined. The existence of the Yellow River was directly interrelated to the uplift of the Tibetan Plateau, the Yellow River could not come into being before the fountainhead had existed in high elevation. There were not rivers similar to today's Yellow River during low-sea level stage in glacial periods. In the last glacial period, the natural environment was very harsh in the north of modern estuary of Changjiang River, some areas were the frozen earth zone and the others were paleo-desert areas. Begining from 12ka BP, the mountain glaciers retreated and sea level got rising. In this process, the Yellow River got more and more water resources and became the modern river system. Accompanying the rising of sea level, the Yellow River delta moved continuously towards the west and entered into the human ages. In study of core E of Laizhou Bay, we find the features of geochemistry have obvious difference in sediments of different period. The changes of grain-size have close relationship to the climate changes, the sand strata maybe correspond to interglacial, the silt strata correspond to glacial epoch. But in the late stage of Upper Pleistocene, the shelf desertization also make sand deposits because of the strong paleo-winter monsoon.
页数	66
语种	中文
文献类型	学位论文
条目标识符	http://ir.qdio.ac.cn/handle/337002/783
专题	海洋环流与波动重点实验室
推荐引用方式 GB/T 7714	韩德亮. 中更新世末期以来黄渤海陆架区衍生沉积体的研究[D]. 中国科学院海洋研究所. 中国科学院海洋研究所,1999.

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