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从距今 18 0 0 0年的最后冰期最盛时期到距今 10 0 0 0年开始的全新世海侵 ,全球气侯发生过急剧的变化。位于亚洲东部的古季风活动也经历了盛衰变化。大量的钻孔及浅地层剖面分析资料已经证实 ,冰期最盛时期陆架区古季风活动加强 ,陆架出现了沙漠环境与黄土沉积。当冰期结束 ,气候转暖 ,冬季风减弱之际 ,南黄海陆架及长江三角洲一带的沙漠与黄土分布范围也随之缩小 ,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变为冷湿气流。长江三角洲地区和陆架上出现了有利于沼泽发育的环境 ,全新世海侵把泥炭层淹没。陆架区晚更新世末期以来的地层中出现沙层、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
The global climate has undergone a drastic change since the heyday of the last glacial period from 1810 to the beginning of the 1000-year Holocene transgression. The ancient monsoon activity in eastern Asia has also experienced ups and downs. A large number of borehole and shallow stratum profile analysis data have confirmed that in the heyday of the Ice Age, the monsoon activities in the shelf area have been strengthened, and desert environment and loess deposits have appeared on the shelf. When the glaciation ended, the climate became warmer and the winter monsoon weakened, the distribution range of the desert and loess in the South Yellow Sea shelf and the Yangtze River Delta narrowed down. The original desert activity area became a loess distribution area, that is, the so-called hard clay deposition Area. With the further decline of the ancient monsoon activity and rising sea level, the northeast wind from the shelf area turns into a cold and wet air stream. An environment conducive to swamp development appeared in the Yangtze River Delta and on the shelf. The Holocene transgression inundated the peat layer. The sedimentary sequence of sand, hard clay and peat layers in the strata since the late Pleistocene in the shelf area, ie “ternary sedimentary structure”, is the best record of the rise and fall of the ancient winter monsoon