Vegetation succession and climate change during the early Pleistocene in the Nihewan Basin,northern China

【作者】 丁国强； 李月丛； Zhen Zhang； Wensheng Zhang； Yong Wang； Zhenqing Chi； Gaihui Shen； Baoshuo Fan；

【Author】 Guoqiang Ding;Yuecong Li;Zhen Zhang;Wensheng Zhang;Yong Wang;Zhenqing Chi;Gaihui Shen;Baoshuo Fan;College of Resources and Environment Science,Hebei Normal University;Key Laboratory of Environmental Evolution and Ecological Construction of Hebei;Key Laboratory of West China’s Environmental System(Ministry of Education),Lanzhou University;Institute of Geology,Chinese Academy of Geological Sciences;

【机构】 兰州大学； 河北师范大学； College of Resources and Environment Science,Hebei Normal University； Key Laboratory of Environmental Evolution and Ecological Construction of Hebei； Institute of Geology,Chinese Academy of Geological Sciences；

【摘要】 The Nihewan Formation,northern China is ideal for studying environmental changes during the early Pleistocene.In conjunction with palaeomagnetic measurements,pollen and grain-size analyses were conducted on 120 samples from a ～24 m long section(2.2-1.8 Ma) of core NHA from the Nihewan Basin,in order to reconstruct past vegetation and climatic changes.The pollen assemblages were dominated by Pinus,indicating that the vegetation was primarily pine forest and that the climate was relatively warm and wet.From 2.15-1.92 Ma,deciduous broad-leaved tree pollen significantly increased to > 10 % of the total,showing that more broad-leaved trees grew in the study area during the warmest and wettest period in the study section.During the Reunion event(2.15-2.14 Ma),increased Quercus but reduced Picea pollen concentrations suggested a transition from a cold to warm climate.From 1.92-1.78 Ma(coeval with the Olduvai event),Pinus and broadleaved tree pollen types decreased.The percentages of Picea(>20 %),Artemisia and Chenopodiaceae increased,indicating that spruce forests expanded,the openness of the forested areas increased and the climate became cold and dry.The vegetation changes reconstructed during the Olduvai period indicates that the climate in the Nihewan Basin was cold and dry,relating to global cooling facilitated by the uplift of the Tibetan Plateau and the strengthening of the winter monsoon.更多还原

【Abstract】 The Nihewan Formation,northern China is ideal for studying environmental changes during the early Pleistocene.In conjunction with palaeomagnetic measurements,pollen and grain-size analyses were conducted on 120 samples from a ～24 m long section(2.2-1.8 Ma) of core NHA from the Nihewan Basin,in order to reconstruct past vegetation and climatic changes.The pollen assemblages were dominated by Pinus,indicating that the vegetation was primarily pine forest and that the climate was relatively warm and wet.From 2.15-1.92 Ma,deciduous broad-leaved tree pollen significantly increased to > 10 % of the total,showing that more broad-leaved trees grew in the study area during the warmest and wettest period in the study section.During the Reunion event(2.15-2.14 Ma),increased Quercus but reduced Picea pollen concentrations suggested a transition from a cold to warm climate.From 1.92-1.78 Ma(coeval with the Olduvai event),Pinus and broadleaved tree pollen types decreased.The percentages of Picea(>20 %),Artemisia and Chenopodiaceae increased,indicating that spruce forests expanded,the openness of the forested areas increased and the climate became cold and dry.The vegetation changes reconstructed during the Olduvai period indicates that the climate in the Nihewan Basin was cold and dry,relating to global cooling facilitated by the uplift of the Tibetan Plateau and the strengthening of the winter monsoon.更多还原