【作者】 覃军干；

【导师】 郑洪波； 吴国瑄； John Dodson；

【作者基本信息】 同济大学 ， 海洋地质， 2006， 博士

【摘要】 在精确AMS碳十四年代测定的基础上，对采自宁绍平原河姆渡钻孔、长江三角洲青浦地区崧泽钻孔的样品进行了孢粉、藻类、有机碳同位素、粒度和磁化率分析，结合考古、历史资料，获得了宁绍平原和长江三角洲地区氧同位素3期(MIS 3)以来的植被、气候和沉积环境变化的记录，在此基础上讨论了人类活动与自然环境变化的关系。MIS 3之前宁绍平原地区孢粉贫乏，植被不甚发育，气候干冷恶劣。MIS 3该地区植被类型是常绿阔叶、落叶阔叶林，气候温暖湿润，末期出现了针叶林扩张，气候较前期偏干，偏冷，是气候恶化的先兆。末次盛冰期(MIS 2)植被稀疏，21308～20001 a B.P.发育了常绿阔叶、落叶阔叶混交林草甸，是该地区整个末次盛冰期气候水热条件最适宜的阶段。全新世植被经历了常绿阔叶、落叶阔叶林，亚热带常绿阔叶、落叶阔叶林，针叶—阔叶混交林，常绿阔叶、落叶阔叶林的演替，反映了气候变化的4个时期，即回暖期、升温期、降温期和接近现代的气候。7626～4957 a B.P.是全新世气候最适宜期。整个全新世气候存在冷暖波动，但其幅度不足以根本改变植被亚热带的性质。长江三角洲青浦地区崧泽孔的孢粉资料反映了与宁绍平原类似的植被和气候变化。该地区末次盛冰期植被不甚发育，其中的针阔叶混交林草甸指示了末次盛冰期存在相对较温暖湿润的阶段。全新世以来植被演替经过了常绿阔叶、落叶阔叶针叶混交林，常绿阔叶、落叶阔叶林，针叶阔叶混交林，常绿阔叶、落叶阔叶林草甸，气候无明显变化。作为全新统的底界，分布在宁绍平原地区的第一硬质粘土层与长江三角洲东部平原区，东海陆架区的第一硬质粘土层，长江三角洲西部丘陵区的风成下蜀黄土均为末次盛冰期时干冷气候条件下的沉积物，为同期异相沉积，硬粘土层形成于淡水环境。河姆渡钻孔所在位置原先是湖泊，冰后期13715～6040 a B.P.，6040～4957 aB.P.和4957～4393 a B.P.受到了海水3次不同程度的影响。该湖泊冰后期开始积水，13715～4393 a B.P.一直是受海水影响的半咸水湖，直到4393 a B.P.开始淡化，4350 a B.P.后历经沼泽化，1050 a B.P.后干涸。受海水影响，该区土壤遭受盐碱化，并在4957～4393 a B.P.达到全新世盐碱化的顶峰。环境变化引起生态系统的变动，可以对史前人类的生产活动产生重大的影响。重大、突然的环境变化，尤其是气候的变化既是推动人类社会发展，促进人类文明出现，同时也是导致史前和历史早期文明崩溃的重要因素。随着全新世海侵的结束和气候最适宜期的到来，优越的环境为河姆渡古人创造了良好的生存条件，河姆渡古人开始在河姆渡遗址周围生活繁衍，这时候人类更多的是去适应自然而不是改造自然环境。5000 a B.P.河姆渡孔所在位置的湖水的扩张淹没了河姆渡先民赖以生活的场所，持续的海侵加上5000 a B.P.姚江倒流造成土地盐渍化日益严重，使农作物减产，是河姆渡先人放弃河姆渡遗址另觅住所的重要原因。随着人类生产力的不断提高，人类对自然环境的影响力也越来越大，植被生态结构的变化是最直接的记录，耕作植被禾本科植物花粉的变化反映了人类对环境的影响的不断深入。更多还原

【Abstract】 This study aims to study the paleoenvironment history of Ningshao Plain andYangtze Delta since the Late Pleistocene. Two sediments were retrieved from the tworegions respectively. One core with length of 45.2 m, was taken from Luojiang, 3 kmto north of Hemudu archaeological site on Ningshao Plain and the other core withlength of 22.9 m, was taken from Songze, 1 km to Songze archaeological site on thelower Yangtze delta. Based on the analyses of multi-proxies of environmental change,namely pollen, dinoflagellate cysts, freshwater algae, magnetic susceptibility, particlesize and organic carbon stable isotope, in combination with evidences fromarchaeological excavations and historical documents, the paleovegetation,paleoclimate, paleoenvironment since Marine Isotope Stages 3(MIS 3) and theinteractions between humans and the environment were discussed.Mixed broadleaved evergreen-deciduous forests developing during the MIS 3suggested a warm, wet climate. Climate of later MIS 3 turned to be cool indicated bythe expansion of conifers.Onset of the Last Glacial Maximum(LGM) was associated with sparsevegetation indicative of the coolest conditions. The cool was interrupted occasionallyby warm, wet conditions marked by mixed broadleaved evergreen-deciduous forestsin Ningshao Plain and mixed broadleaved evergreen-deciduous forests and meadowin the Yangtze Delta.From 13715 to 7626 a B.P., a warm, wet climate fostered the development ofmixed broadleaved evergreen-deciduous forests to grow on surrounding hills anduplands. A large expansion of subtropical evergreen-deciduous broadleaved forestsfrom 7626 to 4957 a B.E represented the mid-Holocene "hypsithermal". From 4957 to 4393 a B.P. the dominance of conifers and the reduction in broadleavedevergreen trees suggest cool, dry conditions corresponding to a Neoglacial periodelsewhere. There are alternate warm and cool climate fluctuations during all theHolocene time, but the extent of the climate fluctuations were not strong enough tochange the vegetation thoroughly. The uppermost hard clay that widely spreads in the late Quaternary strata of theYangtze Delta and Ningshao plain deposited during the LGM. High content ofConcentricystes shows that the formation of the hard clays was influenced by waterand the hard clays should be freshwaters deposits. This was different obviously fromthe Xiashu Loess on the hilly areas of the western Yangtze Delta.During 13715 to 6040 a B.P., 6040 to 4957 a B.P. and 4957 to 4393 a B.P. thesite where core Hemudu lay was influenced by sea water 3 times. The lake developedafter the LGM. It had been a saltwater lagoon since 13715 to 4393 a B.R and turnedto be fresh water lake after 4393 a B.P.. Swampland developed about 4350 a B.P.ago and the water of the lake dried up drastically after 1050 a B.R. Soil here wassalted seriously since MIS 3.There exists close correlation between human activities and the environmentalchanges. Environment changes play an important role in the development of Neolithicculture. Human should harmonize with the environment. The onset of themid-Holocene "hypsithermal" provided favourable conditions for the ancients tomultiply around Hemudu archaeological site. Hemudu archaeological site wasinundated by the flood about 5000 a B.P.. The durative transgression combined bythe change of Yaojiang’s course salted the soil seriously and reduced the output of therice. About 5000 a B.E people had to abandoned this area.The increasing of Gramineae content shows that with the range expanding andintensity increasing of human activity, human activity has become one of theimportant factors to affect the environment.更多还原