太行山山前平原区早更新世以来沉积物粒度与磁化率特征及其环境意义

Characteristics of Grain Size and Magnetic Susceptibility of Sediments and Their Environmental Significance in Piedmont Plain of Mt.Taihang since Early Pleistocene

通过对太行山山前平原邯郸地区HDZKF孔的粒度和磁化率分析,探讨了早更新世以来该地区沉积物粒度特征、磁化率特征、水动力条件及古气候环境演变。研究表明,邯郸地区先后经历了5个阶段的环境演化:(1)早更新世地层为洼地沉积,水动力条件平稳,磁化率值较高且波动大,气候温暖湿润,对应倒四冰期之后的间冰期;(2)中更新世地层为河流环境沉积,水动力条件增强,磁化率值较为稳定,气候总体较为寒冷干旱,对应倒三冰期与倒二冰期;(3)晚更新世气候由温和潮湿迅速转为寒冷干旱,磁化率值低且波动小,水动力条件平稳低能,沉积环境以河流为主,对应末次间冰期与末次冰期;(4)全新世早期水动力条件增强,总体为以泛滥平原为主的沉积环境;(5)全新世晚期气候温暖湿润,处于水位上升的湖沼环境阶段,磁化率值最高,与中粉砂(5~6φ)呈正相关,水动力条件弱,对应冰后期。

The grain size and magnetic of sediments from core HDZKF in Handan area of the piedmont plain of Mt.Taihang were analyzed.The grain size characteristics,magnetic susceptibility characteristics,hydrodynamic conditions and the evolution history of paleoclimate and environment in the area since the Early Pleistocene were discussed.It is found that the study area has experienced five periods of environmental changes since the Early Pleistocene:(1)The Early Pleistocene strata are depression deposits,and the hydrodynamic conditions are stable.The magnetic susceptibility value is high and fluctuates greatly.The climate is warm and humid,corresponding to the interglacial period after the fourth to last glaciation;(2)The Middle Pleistocene strata are fluvial environmental sediments,and the hydrodynamic conditions begin to strengthen.The magnetic susceptibility is generally stable.The climate is generally cold and arid,corresponding to the third to last glaciation and the penultimate glaciation;(3)In the Late Pleistocene,the climate quickly changed from mild and humid to cold and dry,with low magnetic susceptibility and small fluctuations.The hydrodynamic condition is stable and weak,and the sedimentary environment is mainly river,corresponding to the last interglacial period and the last glaciation;(4)The Early Holocene enhanced hydrodynamic conditions,and the sedimentary environment is dominated by flood plains;(5)In the Late Holocene,the climate was warm and humid,and it was in the stage of lake and marsh environment with rising water level.The magnetic susceptibility value is the highest,which are positively correlated with medium silt.The hydrodynamic condition is weak,corresponding to the post glacial period.