摘要:
通过对河北白洋淀老河头剖面全新世沉积物岩性特征、地层层序、粒度组成及微体古生物组合等进行综合研究,重建了白洋淀全新世以来的环境演变过程。全新世以来白洋淀沉积特征所反映的气候环境特征表现为早期开始出现湖沼相沉积,气候寒冷偏湿;中期湖泊沉积发育,气候温暖湿润;晚期湖泊退缩,以河流-沼泽相沉积为主,气候向凉干转变。综合沉积特征、环境演变阶段与加速器质谱(AMS)14C测年资料对白洋淀全新统沉积序列进行系统分析,并将全新统划分为三段:下全新统(11000—8500 a)以灰黄色粉砂质粘土、粉砂为主,夹黑色粘土,冲积-湖沼相沉积发育;中全新统(8500—3200 a)为灰黑色粘土夹粘土质粉砂,湖沼相沉积发育;上全新统(3200 a~)以黄色、褐黄色粉细砂、粘土质粉砂为主,冲积-沼泽相沉积发育。白洋淀全新统中段含有黑色粘土沉积和大量微体与腹足、双壳类等古生物化石,为华北地区全新世地层的划分及区域对比提供了依据。
关键词:
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白洋淀
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全新统
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沉积特征
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地层划分
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粒度
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双壳类
Abstract:
Through a comprehensive study of the lithology, stratigraphic sequence, grain sizes, and microfossil assemblages of sediments from Laohetou section in Baiyang Dian, Hebei Province, the authors reconstructed the Holocene environmental evolution in Baiyang Dian. During the early Holocene, the climate conditions became cold and wet. Limnological conditions changed significantly after middle Holocene, and then lake retreated at the late stage of the Holocene. Based on the analysis of sedimentary features, environmental evolution and AMS14C dating data of Laohetou section in Baiyang Dian, the authors detected significant variation in sediments of Laohetou section related to sedimentary facies and climate change. Holocene Series in Baiyang Dian can be divided into three stages. Early Holocene (11000–8500 a) was alluvial and limnological facies of yellow silty clay, silty sand; Middle Holocene (8500–3200 a) was a climate optimum for the development of limnological facies of black clay and clayey silt; Late Holocene (3200 a~) was characterized by the development of alluvial, swamp facies. Middle Holocene contains black clay deposits in Baiyang Dian and provides a basis for the Holocene division and regional correlation in North China.
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