1.8-1.0Ma泥河湾盆地植被和气候变化及对古人类演化的影响

1.8-1.0Ma is an important period both for the study of vegetation and climate change and for their relationship with hominin evolution. During this period, the orbital scale of climate variability and amplitude changed obviously, hominins appeared and began to migrate on a large scale. The Majuangou section in the Nihewan Basin was formed at about 1.8-1.0Ma with about 80m in depth, and containing series of early Pleistocene Paleolithic sites with the earliest, longest lasting time and the most complete cultural sequence in East Asia at present. Based on the study of archeology and paleoanthropology, at least different 15 cultural layers and three stone technology stages can be recognized. However, the paleoenvironment research is relatively weak, and which make the relationship between human evolution and environment change remains unclear. In this project, the MajuanGou section was chosen as the research object. Samples were collected for all the section at intervals of 10-20cm including cultural layers and the natural layers. Pollen assemblage analysis and other proxy indices such as grain size, organic matter contents and geochemical element analysis were carried out to establish high resolution vegetation succession and climate change series from 1.8 to 1.0Ma in the Nihewan Basin, and then try to reveal the similarities and differences of vegetation composition and climate change characteristics in different hominin evolution stages and in different archaeological cultural periods, and discuss the physical link between the development of stone technology and the succession of vegetation and climate change. The study on vegetation succession and climate change at 1.8-1.0Ma in the Nihewan Basin will provide important scientific evidences for better understanding the relationship between hominin evolution and environmental change in the early Paleolithic period.

1.8-1.0Ma是进行环境演变及与人类演化关系研究的重要时段。此间，轨道尺度气候变率和变幅发生变化，直立人大规模迁徙。泥河湾盆地马圈沟剖面形成于约1.8-1.0Ma，含有东亚目前年代最早、持续时间最长的早更新世旧石器遗存。考古与古人类学研究认为，该剖面至少包含15个文化层，其石器技术经历了3个发展阶段。然而古环境研究相对薄弱，人类演化与环境演变的关系仍不清楚。本项目选择马圈沟剖面为研究对象，以10-20cm间隔采集剖面文化层和自然层样品，开展孢粉及粒度、有机质等常规代用指标分析，建立1.8-1.0Ma泥河湾盆地植被演替和气候变化的高分辨率时间序列，揭示不同人类演化阶段、不同文化期的植被面貌和气候特征及其相似性和差异性，探讨石器技术发展与盆地植被演替和气候变化之间的物理关联。1.8-1.0Ma泥河湾盆地植被演替与气候变化研究将为深入理解旧石器早期人类演化与环境演变的关系提供重要科学依据。

本项目通过马圈沟遗址群3个剖面和NHA钻孔共计1455块样品的孢粉、粒度等指标分析，结合现代表土数据库和现代相对花粉产量数据定量，重建了泥河湾地区早更新世（1.8-1.0Ma）以来植被与气候变化过程及人类活动时期及其前后的植被及气候变化特征。.马圈沟遗址群剖面的孢粉及粒度分析结果显示：马圈沟遗址和鱼咀沟遗址多数文化文化层出现时期（1.75-1.39 Ma）气候总体较为稳段且变幅较小，变幅在4℃左右，为低偏心率时期。1.39-1.32Ma期间，气候变幅增大，温度变幅可达12℃。多数文化层出现时期属于森林草原或草原景观，气候为冷转暖过程中，古人类生活于湖滨开阔的水边，景观开放度高于80%；另外2个文化层（1.64Ma和1.32Ma）是以松属为优势种森林景观，景观开放度多高于60%；而文化层之间的自然沉积地层多为以云杉属或松属植物为主的森林景观时期，景观开放度低于50%，不论哪个遗址，云杉花粉占优势时期，均没有古人类活动遗迹。. 古湖中心NHA钻孔孢粉分析显示在 1.78-1.0Ma 期间气候总体比现今湿润，绝大多数时段年均降水量（Pann）高于450mm，期间出现多次冷暖波动。植被总体以森林景观为主，乔木植物盖度多高于50%，且多数时段为以松为主的暖温带针叶林，期间也出现了3次温带草原和5次寒温带针叶林的明显扩张时期。所有代用指标均能表现出显著的~20kyr 变化周期，可信度均高于95%，此周期是对受岁差驱动的东亚夏季风变化周期的响应。多个代用指标也存在较为显著的~100kyr周期，是仅次于~20kyr 周期的主导周期。泥河湾盆地中更新世转型发生在 1.30-0.74 Ma，以气候显著变冷、变幅明显增大、变化频率加快，~100kyr 周期增强为主要特征。此时期是泥河湾盆地整个研究段植被和气候变化最为剧烈的时期，5次持续时间较长的寒冷的阶段。