1.2Ma以来闽中沿海长乐红色风化壳剖面的地球化学记录及古气候意义

The geochemical records and their paleoclimate significance of the red weathering crust at Changle coast in central Fujian since 1.2 Ma

对闽中沿海长乐厚度8m的红土风化壳剖面(CL)间隔5cm采样,进行地球化学元素和粒度组成测试,以OSL与ESR年龄确定年代学框架,据此探讨了1.2Ma以来红土沉积常量化学元素含量、组合及其比值记录的区域气候环境变化特征.结果表明,1.2Ma以来CL剖面第四纪红土风化强度介于红壤型风化壳和赤红壤型风化壳之间变化,表现为中亚热带和南亚热带过渡区红土风化壳特点;早更新世晚期为赤红壤型风化壳向红壤型风化壳转变,反映区域气候由湿热向较暖湿气候过渡;中更新世为红壤型风化壳向赤红壤型风化壳的过渡,反映区域气候由相对暖湿过渡到明显湿热的变化;晚更新世早期发育典型赤红壤型风化壳,区域气候呈现湿热气候特征;晚更新世晚期由湿热向温干转变,早期赤红壤型风化壳有向现代红壤风化壳的逆行演替趋势.CL剖面记录的气候变化特征符合全球气候变化规律,东亚季风系统中夏季风盛衰变迁控制了研究区红土风化壳类型的动态变化.

The chemical weathering intensity and element migration features of the red weathering crust at Changle in central Fujian（Changle RWC） are studied by samples collected from the 8-meter-thick section at a interval of five centimeters in this paper.Based on the measurement of the geochemical elements and mechenical grading,the chronology of Changle RWC is identified by combing OSL and ESR.Then,the process and features of the regional climatic change recorded by the contents,composition and ratio of the major chemical elements of Changle RWC since 1.2 Ma are analyzed.The results indicate： 1） the weathering intensity of Changle RWC in quaternary period was relatively strong between that of red soil and latosolic red soil weathering crusts,with typical characteristics of the red weathering crust in the transition zone between mid-subtropical zone and south subtropical zone;2） in late Early Pleistocene,Changle RWC transformed from lateritic red soil into red soil,indicating that the climate changed from damp-heat to relatively warm-humid;3） in middle Pleistocene,Changle RWC experienced a transition from red soil to lateritic red soil,indicating that the climate changed from relatively warm-humid to damp-heat;4） at early Late Pleistocene,Changle RWC developed to typical lateritic red soil,indicating a damp-heat climate;5） at late Late Pleistocene,Changle RWC showed a trend of retrogressive succession from latosolic red soil to late red soil,indicating the climate change from warm-humid to warm-dry.The climate change characteristics indicated by Changle RWC are corresponding to the global climatic variation law.At the same time,it is of its own characteristics,due that the regional climatic variation is contoled by the change of summer monsoon.