宁绍平原中全新世气候-海平面波动与河姆渡文化演化的耦合研究

The mid-Holocene climate change, sea level fluctuation and the associated Neolithic human activities at coastal area become more and more attractive to researchers during the past decades, as the global warming and sea level rising accelerate persistently. However, sea level fluctuation was subtle and sea level standstill was too short during mid-Holocene, making not only dating materials unavailable but also sedimentary facies unidentifiable. Therefore, to establish a high resolution sea level curve of Holocene became a critical issue. Ningshao Plain, where the famous Hemudu Neolithic culture was originated, would provide answers to some hotly debated issues, such as relation between climate-sea level changes and the spatiotemporal evolution of Hemudu Neolithic culture, if more researches and studies were carried out. This proposing program intends to comply a systematic research on the Holocene sedimentary record in the Yaojiang Valley. Multiple proxies will be employed for distinguishing sedimentary microfacies of tidal flat, including sediment lithology, grain size analysis, magnetic property measurement, and biogenic traces recognition, then to set up an empirical sea level formula. The local tidal range will be considered to reconstruct paleo sea level fluctuation on the basis of a high resolution chronological sequence, which is provided by both the pollen fossil and basal peat AMS 14C dating. Pollen analysis, magnetic properties of sediment, and the XRF core scanning are applied to recover the Holocene climate changes. Furthermore, the most recent progress of archaeological study on Hemudu Neolithic culture will also be referred to discuss the impact of environmental change on the Hemudu Neolithic culture evolution. This study can shed light on the understanding global environmental change and regional response on the coastal lowlands.

在全球变暖、海平面持续上升背景下，中全新世暖湿气候与海平面波动及其影响下的海岸带新石器人类活动引起越来越多的关注。中全新世海平面变化具幅度小、停顿时间短等特点，其沉积记录不易辨识，定年材料不易获取，准确重建古海平面曲线成为难点和重点。宁绍平原是我国新石器河姆渡文化发源地，文化发展与自然过程（气候、海平面波动、海岸环境等）的耦合关系尚缺少深入研究。本申请课题拟通过杭州湾南岸全新世沉积记录的系统研究，采用粒度、沉积构造、环境磁学、生物遗迹化石等多指标分析，识别潮滩沉积微相，建立海平面经验公式；运用孢粉化石、盐沼泥炭作为AMS 14C测年材料，建立高分辨率地层年代框架，基于潮差变化重建中全新世高分辨率海平面曲线。综合孢粉、环境磁学及XRF岩芯扫描等方法恢复全新世古气候特征。参考新近河姆渡文化考古进展，探讨自然过程对河姆渡文化演化的影响，也为全球变化及区域响应研究提供典型案例。

宁绍平原是我国东部沿海地区重要的生活圈，也是新石器文化的重要发源地，为研究全新世气候-海平面波动下的人类活动响应提供了典型案例。本课题通过姚江谷地的野外调查和9支沉积物钻孔的钻探，结合大量的测年资料和实验室分析工作，勾勒出姚江谷地全新世的地层演变格局，恢复了海平面波动的基本模式及其影响下的地貌环境演变过程。揭示了在此环境影响下河姆渡文化的发生发展过程，并讨论了其最终衰落的原因。研究的主要结论概括为：姚江谷地在9200 cal yr BP 之前为下切河谷，河谷深约30-40m，呈现西高东低的地貌格局。随后，在9200-7900 cal yr BP, 全新世海侵介入姚江谷地，形成广阔的河口湾环境。7900-7600 cal yr BP期间海平面稳定，姚江谷地逐渐开始海退成陆，在7600 cal yr BP前后，谷地的中部率先成陆，成陆范围在随后的1400年逐渐向东推进至慈城以东地区。在此过程中，谷地中部率先于7600年前发育半咸水的沼泽环境，大约6200 cal yr BP前后，淡水湖沼广泛发育，一些海拔较高的地区率先成陆。至5500年前，姚江谷地大部分地区都已成陆，形成冲积平原环境。这样的环境转变，即海相-湖沼相，湖沼相-陆相，吸引并促进了河姆渡文化在此诞生和发展。该研究填补了河姆渡文明发展地质背景不明的重大空白，为深入理解全新世人地互动关系提供了可靠依据。