郑州地区全新世以来沉积物地球化学风化特征及其古气候意义

Geochemical Weathering Characteristics of Sediments in Zhengzhou Area Since the Holocene and Their Paleoclimatic Significance

文章对郑州地区钻孔剖面全新世沉积物中常量元素和微量元素的地球化学特征进行分析,结合光释光和14C测年数据,A-CN-K图解、A-CNK-FM图解、化学风化指数(CIA)、退碱系数(Bc)、Na/K值、Rb/Sr值、Ba/Sr值等指标,探讨该地区全新世以来沉积物化学风化特征及其古气候意义,并成功反演出古降雨量和古气温数据,重建了全新世古气候演变序列。结果表明,该钻孔剖面沉积物全新世以来整体处于低等化学风化阶段,全新世古气候相对稳定,整体温暖湿润,年均古降雨量639.69 mm,年均古气温11.78℃。依据古气候演变序列,可将全新世古气候划分为4个干冷事件和1个暖湿事件,自古至新依次为新仙女木(Younger Dryas)干冷事件、8200a BP干冷事件、6600a BP干冷事件、4200a BP干冷事件、晚全新世暖湿气候事件。第一次干冷事件强度最大,古降雨量和古气温较现今郑州地区分别低155.77mm和5.49℃,暖湿气候事件较现今郑州地区分别高282.23mm和2.16℃。

The work analyzed the geochemical characteristics of major and trace elements in the Holocene sediments of the Zhengzhou area.Optically stimulated luminescence(OSL)and 14C dating data,A-CN-K diagrams,A-CNK-FM diagrams,chemical weathering index(CIA),alkali reduction coefficient(Bc),Na/K value,Rb/Sr value,and Ba/Sr value were utilized to explore the chemical weathering characteristics of sediments and their paleoclimatic significance in Zhengzhou area since the Holocene.The Holocene paleoclimate evolution sequence was reconstructed by the inversion of ancient rainfall and temperature data.Results indicate that the sedimentary profile of the borehole has been in a low chemical weathering stage since the Holocene.The Holocene paleoclimate was relatively stable,overall warm and humid,with an average annual paleorainfall of 639.69 mm and an average annual paleotemperature of 11.78℃.According to the sequence of ancient climate evolution,the Holocene paleoclimate can be divided into four dry and cold events and one warm and humid event.From ancient to modern times,they were the Younger Dryas dry and cold event,8200a BP dry and cold event,6600a BP dry and cold event,4200a BP dry and cold event,and Late Holocene warm and humid climate event.The Younger Dryas dry and cold event had the highest intensity,with ancient rainfall 155.77 mm and ancient temperature 5.49℃lower than those in present-day Zhengzhou,and the late Holocene warm and humid climate event was 282.23 mm and 2.16℃higher than those in present-day Zhengzhou.