摘要:
末次冰期最盛时期,干、冷气候盛行,渤海、黄海的大部分地区出现沙漠化,形成众多的沙丘。随着干冷气候的减弱,长江三角洲一带出现硬粘土沉积。冰消期的到来,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,出现了有利于沼泽发育的环境,以致全新世海侵前夕往往形成薄层泥炭沉积。晚更新世末期以来古冬季风发生、发展和衰退过程与沙漠、硬粘土和泥炭层形成过程相对应。
Abstract:
The paleao-monsoon activities in East Asia experienced a change of vicissitudes since 18 kaBP. In the maximum phase of last glacial age,dry and cold climate prevailed,resulting in the desertization in most part of the Bohai Sea,the Yellow Sea and the East China Sea. Then,with the withering of dry and cold climate,there appeared stiff clay sediment in the delta of the Changjiang River. Because the further declining of paleao-monsoon and the gradual rising of sea level after 15ka approached,the northeast wind from shelf area was not the dry and cold air-current any more,but the cold and damp one with higher humidity,which produce an advantageous environment for the development of the swamp. As a result,a thin-layered turf was formed before the seawater transgression in Holocene. The developing process of the paleao-monsoon since the last stage of late Pleistocene is well correspondent to the formation of shelf desert, stiff clay and turf layer respectively. It is suggested that the such sequences in the delta region of the Changjiang River may be the best record of the vicissitudes of the palaeo-monsoon.
下载: