【摘要】 通过分析钻孔资料了解,杭嘉湖平原全新世沉积之下,有两层硬土层。上层硬土层的顶板为本区全新世沉积的下限。晚更新世末,本区为缓起伏的丘陵、台地。南缘为古钱江谷地;西侧(湖州至杭州之间)为古钱江的一条支谷,呈南北向。在这个基础上,全新世早、中期海侵时南缘成为海湾,西侧为河口湾。海侵最盛期时,全区除小块区域外,多属潮坪或潟湖。全新世晚期,西侧的河口湾淤浅阻塞,全区被淤积为淡水湖沼平原。更多还原

【Abstract】 This paper tackles this problem based upon a variety of sedimentological evidence, such as paleomicrofauna, pollen and spores, sediment grain size, sedimentary structure, heavy mineral content and 14C radio-carbon dates. These data were mainly, in conjunction with nearly 200 subsurface drilling cores available in this area, collected from seven newly drilled cores at Gou-ting, Gaoqiao and Shuanlin etc. The results obtained from this study could be summarized as follows:1. A tenacious-clay layer with a greyish or yellowish brown colour identified as river-lakemarsh deposits of late Pleistocene exists, with few exceptions, beneath surface Holocene deposits. This layer can be used as a marker defining the boundary between Holocene and Late Pleistocene depositions.2. The topography of the palaeo-surface of the Late Pleistocene, Which presenting an inter-fingered pattern, is in general a major relatively elevated platform with elevation within -5m and is crossed by a south-to-north orienting valley about 15──25 m in elevation running between the platform and the western hilly land from Taihu lake to the Qiantang Jiang River. Another depressed valley exists southeast of the platform trending from Haiyan to Jinshanwei, whose elevation is no greater than -20 m.3. The evolution of Holocene sedimentary environments in this area can be divided into three periods:1) Early period (about 10000-7500 Y. B. P.) Environmentally, the platform was terrestrial transited to low-salinity marshes; while west of the platform estuarian and south of it a coastal embayment.2) Middle period (7500-2500 Y. B. P.) In the early stage of this period, the western part was an estuary, the area around Ganpu and Zhapu a coastal bay and the platform was altered into tidal flats and low-salinity marshes. The northeast portion and parts of the southwest portion then were low-salinity marsh environment. During the second stage, the platform was turned into low-salinity marshes except for its northeast and southwest portion which were fresh water marshes; the southern shallow bay was silted up into land and the western estuary was shallowed and silted into a narrow boy connecting Tai Lake with the Qiangtang River. In the last stage, the platform developed further into an area fresh-water lakes and marshes,and a number of fresh-water lakes developed in the northeast; the western channel became silted up.3) Late period (the last 2500 years) In most of the study area fresh-water lakes and marshes dominated. At the time of about 2000 Y. B. P. the western channel became isolated from the Hangzhou Bay and was transformed into some small fresh-water lakes.更多还原