通过对浙江余姚河姆渡-田螺山遗址附近的HMD1501和HMD1502两个钻孔的微体古生物学研究,揭示了该地区全新世以来的植被演变、气候变化、海平面变迁及人类活动。孢粉、海相沟鞭藻、淡水藻类及有孔虫内衬的记录表明: (1)在早全新世(对应于镇海组下部),植被群落属于常绿阔叶和针叶混交林,气候温暖潮湿,研究区属于海侵阶段。(2)在中全新世(对应于镇海组中部),植被群落虽仍为针阔叶混交林,但气候转为温和湿润,研究区仍属于海侵阶段。(3)由于人类活动的进一步加剧,在晚全新世(对应于镇海组上部)的植被群落中草地的面积也随之扩大,并在滨海地区开始有一些以莎草科为主的沼泽地形成,植被群落属于针阔叶混交林-草地,气候更加凉爽干燥,研究区转为海退阶段。(4)在~7235-3327 cal. yr B.P.期间,草本花粉的含量激增,特别是一些粒径不小于35mum 的禾本科栽培作物花粉的含量增加,说明此时人类活动开始增强,河姆渡-田螺山遗址附近出现较多的水稻种植区。
英文摘要:
Micropaleontological record of the two boreholes(HMD1501 and HMD502)from Hemudu-Tianluoshan Sites in Yuyao of Zhejiang Province,reveals a detailed vegetation history,paleo-vegetation evolutions,palaeoclimate change,fluctuating sea level and human activity in the study area during the Holocene.Palynological results(pollen,spores,dinoflagellate,freshwater algae and foraminifer linings)suggest that: (1)Evergreen coniferous and broadleaved mixed forest developed during the Early Holocene(corresponding to the lower of Zhenhai Formation),the climate was warm and humid,and the study area was belong to a transgression stage. (2)Evergreen coniferous and broadleaved mixed forest were still developed during the Middle Holocene(corresponding to the middle of Zhenhai Formation),the climate changed into moderate and humid,and the transgression continued. (3)Due to human activity,coniferous and broadleaved mixed forest-grassland developed during the Late Holocene(corresponding to the upper of Zhenhai Formation),the climate changed into cold and dry,however,the study area began to enter a regression stage. (4)Human activities began to strengthen,and high percentage Poaceae pollen(≥35mum)indicates rice culture activity presented at Hemudu-Tianluoshan Sites during the ca.7235-3327 cal.yr B.P..