通过对澧阳平原野外调查,多剖面地层对比分析及岩板垱(YBD)剖面样品的粒度、地球化学元素分析和年代测定,揭示该区晚更新世晚期至全新世早中期环境演变,并探讨其对人类活动的影响。研究结果表明,30~6 ka B.P.间,澧阳平原由冲沟发育的黄土台地向河湖发育的平原丘岗地貌过渡;气候环境经历了弱暖湿-气候变差-凉湿-波动回暖-暖湿的变化;更新世末至全新世早期稻作农业的出现与该区的环境条件和文化基础密切相关;环境演变也推动了古人类活动范围和聚落特征的变化。
英文摘要:
Based on detailed field surveys, comparison of strata of typical profiles and experimental analysis (including grain size, geochemical analysis and optically stimulated luminescence (OSL) dating) of samples collected at the Yanbangdang (YBD) site, we explored the environmental evolution from Late Pleistocene to Middle Holocene and its impact on human activities, especially on the origin and development of rice agriculture in Liyang Plain. The results showed that the climate of the Liyang Pain during 30-6 ka B.P. experienced five stages:relatively warm and humid in the Late Pleistocene, cool and humid during the Last Glacial Maximum (LGM), fluctuated warming in the terminal Pleistocene and Early Holocene, and warm and humid during the Middle Holocene. In the Late Pleistocene, landforms of the Liyang Plain were characterized by tablelands drained by rivers and gullies in the Late Pleistocene, with topographic relief much higher than present. As climatic amelioration during the terminal Pleistocene and Early Holocene, continuous filling and siltation occurred in Liyang Plain and large areas of wetland was formed. Landscapes of the Liyang Plain at this time were mainly plains and hillocks with dense rivers and lakes and the topographic relief was gradually reduced. During the Middle Holocene, landforms of Liyang Plain were mainly alluvial and lacustrine plains with scattered mounds and hillocks. Under the relatively suitable environmental condition of the Late Pleistocene, the Late Paleolithic human activities existed continuously in Liyang Plain especially in the surrounding mountain and hill areas. Climate cooling during the LGM did not cause severe damages to regional ecosystem and ancient people also took steps to temperature drop, which allowed continued development of transitional culture from the Paleolithic to the Neolithic in Liyang Plain. Liyang Plain had favorable environmental conditions (e. g., abundant moisture, proper temperature, suitable landforms and rich fertile soil) and solid cultural foundation (continuous human activities and a long history of rice exploitation) in Early Holocene, which contributed to the origin and development of rice agriculture in this area. The warm and humid of the Middle Holocene climate promoted rice agriculture to a new level and the Neolithic culture expanded to the lower flat plain areas.