【作者】 李超；

【导师】 戴雪荣；

【作者基本信息】 华东师范大学 ， 自然地理学， 2011， 硕士

【摘要】 本文以苏州澄湖古湖沼洼地沉积记录为研究对象,探讨在全新世气候和海平面变化背景下,湖底古湖沼洼地的形成演变过程及沉积记录所揭示的全新世海侵事件。通过对SC4孔沉积物的岩性观察,AMS14C测年,磁化率测定及粒度、有孔虫、有机质碳同位素、有机质等实验分析,结合历史文献和课题组其他钻孔的研究结果,本文获得以下初步结论：1.苏州澄湖湖底古湖沼洼地全新世以来主要经历了以下三个演化阶段：第Ⅰ阶段：全新世早期(10kaBP～7.0kaBP)以河流(沟谷)侵蚀为主,末次冰期形成的硬粘土平原随着沟谷系统的下切和扩大形成众多台地和沟谷相间的地貌景观,推测湖沼洼地就是这个时期形成的。第Ⅱ阶段：全新世中期(7.0kaBP～5.8kaBP)以堆积作用为主,平均沉积速率为0.39cm/a,古洼地及古河道被快速填充,并大致经历了由暴露地表向沼泽过渡—沼泽—受海水影响—受河流扰动演变过程。第Ⅲ阶段：全新世中后期(5.8kaBP～今)沉积环境以侵蚀作用为主,沉积缺失,后期澄湖形成演化,硬粘土平原和湖沼洼地演化为湖底的一部分,湖泊环境下,现代沉积缓慢。2、有孔虫分析证实,全新世期间该地区曾经发生过一次海侵,时间大约在全新世中期(相当于镇江海侵),与前人基于微古分析的研究结果基本一致。有孔虫的属种少、数量少、壳径小,由此表明此次海侵规模、范围均相对较小,可能仅在澄湖以东以及西部的河谷地带及地势低洼的湖沼地区分布。结合SC4孔有机质碳同位素分析与SC1孔孢粉分析,认为海侵发生在全新世高温期。3、全新世中期以来,澄湖湖底西侧湖沼洼地地势低洼,不利于人类生存,没有遗址分布,但在湖沼洼地周围发现了众多新石器聚落遗址,这可能与湖沼洼地既利于渔猎有利于农耕的地表环境有关。考古发现的席墟聚落遗址位于吴淞江入澄湖的汊流——席墟浦河口东侧,为地势相对较高的湖滩和湖底。这从一定程度上说明全新世海平面波动变化与海岸线变迁影响在很大程度上控制着本区文化遗址的迁移和扩散。更多还原

【Abstract】 This paper takes Suzhou Chenghu as the research object, focusing on the paleo-limnological formation and evolution at Suzhou Chenghu and the Holocene transgression revealed by sedimentary records at the background of the climate and sea level changes at Holocene. Through a comprehensive analysis of the mud hole sediments of lithological depression at SC4, AMS14C dating, magnetic susceptibility, grain size, foraminifera, organic carbon isotope, TOC/N and organic matter, combined with historical documents and integrating the research of other drillings at Chenghu in Suzhou, the following preliminary conclusions were obtained in this paper:1. Since the Holocene, the paleo-limnological sedimentary environment has experienced the evolution of the following three main stages at Chenghu:The first stage:The depositional environment dominated by river (valley) erosion at the early Holocene (ten thousand～7.0kaBP). With the incised and expansion of valley system, the hard clay plains formed at the last glacial period developed numerous terraces and valley landscapes, which suggested that the paleo-limnological formed during this period.The second stage:the middle Holocene (7.0～5.8kaBP) sedimentary environment dominated by accumulation and the average deposition rate increased with about 0.39cm/a. The paleo-limnological and paleo-channel were filled quickly.And the paleo-limnological experienced the evolution of from the exposed surface to marsh-marsh-affected by sea water-disturbance by the river;The third stage:in the late Holocene (5.8kaBP～Present), the sedimentary environment was the erosion and the sedimentary was missing. Later, Chenghu formed and is evoluting, and the hard clay plain and the paleo-limnological were evolved into a part of the lake’s bottom and the average deposition rate was low.2.Study on foraminifera confirmed that there is a transgression event occurred at the region during the Holocene. The time of Holocene transgression was in the mid-Holocene (the equivalent of Zhenjiang transgression), basic consisted with previous researches based on the microfossil analysis.The analysis shows that the scale and the scope of the middle Holocene transgression are relatively small and the transgression strata only exists in the east and west of Chenghu valley and the low-lying lake areas. Combined with organic carbon isotope analysis of SC4 and pollen analysis of SC1, mid-Holocene transgression occurred in the Holocene high temperature phase.3. Since the mid-Holocene, the west Chenghu quagmire was low-lying and was not conducive to human existence but a large number of Neolithic settlement sites were found near the paleo-limnological, and this should be related to the surface environment and this not only conducive to hunting and fishing but also to farming. And the Xixu archaeological settlement sites in the branch of Wusong River into the Chenghu-east side of Xixu Pu River with the relatively high-lying lake’s beach and the lake’s bottom.All of those show that the migration and proliferation of cultural sites can be explained by the Holocene sea-level changes and coastline changes to some extent.更多还原