MIS 5以来长江三角洲地区沉积环境演变的光释光年代证据  

Luminescence chronology constraints on the sedimentary stratigraphy of the Yangtze River delta since the last interglacial

作　　者：高磊[1] 隆浩[1] GAO Lei;LONG Hao(State Key Laboratory of Lake Science and Environment,Nanjing Institute of Geography and Limnology,Chinese Academy of Sciences(NIGLAS),Nanjing 210008,Jiangsu)

机构地区：[1]中国科学院南京地理与湖泊研究所,湖泊与环境国家重点实验室,江苏南京210008

出　　处：《第四纪研究》2023年第1期33-45,共13页Quaternary Sciences

基　　金：国家自然科学基金项目(批准号:41807417和41977381);中国科学院(B类)战略性先导科技专项项目(批准号:XDB40010200)共同资助。

摘　　要：长江三角洲是我国东部陆架-海岸沉积体系的重要组成部分,是研究三角洲环境演化和人类活动的理想区域之一。前期大量的研究成果主要聚焦于冰后期和全新世长江三角洲响应海面上升的演进过程,而冰期-间冰期尺度的长江三角洲地区沉积环境变化的研究因年代学工作薄弱而进展缓慢。本文在近年来对长江三角洲地区晚第四纪沉积物开展一系列石英OSL和钾长石(混合矿物)红外释光(pIRIR)测年研究,且已取得一定的释光测年数据的基础上,简要地梳理和总结长江三角洲末次间冰期以来区域沉积环境演化的研究进展,着重分析晚更新世以来长江三角洲南北两翼沉积地层的年代框架异同、释光年代约束下末次冰期长江古下切河谷的演化历史及成因。释光测年及区域地层对比研究结果表明:1)氧同位素(MIS)5e阶段(130~120ka)和全新世,长江三角洲地区沉积环境受海洋作用影响比较明显。2)MIS 3阶段是否存在海侵环境,不同测年技术得出了不同的年代学结论。且认为^(14)C和常规的石英OSL测年得到的末次冰期早期地层(MIS 3~4)的年龄很可能都存在低估,而钾长石或混合矿物红外释光测年可以发挥一定的测年优势。这也需要后期继续强化区域地层的年代学测试和对比研究。3)在MIS 4/2阶段,长江三角洲南北两侧及主体平原均以陆相沉积环境为主。本研究结果可为全球或区域性大河三角洲及海岸系统响应末次间冰期以来海面变化的沉积历史对比研究提供参考。The Yangtze River delta region is a significant section of Chinese coastal-shelf sedimentary system and one ideal place to investigate delta sedimentary evolution and human activities.In past decades,numerous studies have focused on the post-glacial estuary and Holocene delta sedimentary processes in response to rapid sea-level rise.However,there has been limited research work about the sedimentary evolution of the delta on glacial-interglacial timescales.Based on quartz optically stimulated luminescence(OSL)and K-feldspar/polymineral post-infrared(IR)infrared stimulated luminescence(pIRIR)dating of six long sediment cores(JCP01,YZ07,YD006,YD014,EGQD14 and YD016),together with a compilation of regional chronostratigraphy from previous studies,this study explored the sedimentary history of the Yangtze Delta and the sedimentary stratigraphy evolution in this region(31°~34°N,119°~120°E)since Marine Isotope Stage(MIS)5.In particular,we analyzed the similarities and differences of the sedimentary environments between the southern and northern delta plain as well as possible reasons.Our results showed that two distinct transgressive events around the northern Yangtze River delta plain were recorded in the MIS5 and Holocene stratigraphy,influenced by relatively high sea level at then.However,it seems to have no consistent dating or reliable chronological evidence for the"MIS3 transgression"in the northern Yangtze Delta because both ^(14)C and quartz OSL ages are closed to saturation and thus age underestimation.In contrast,K-feldspar or polymineral pIRIR dating has advantage for sediments dating in this region.Thus,a ca.130ka terrestrial-marine interaction sedimentary history of the northern Yangtze River coastal plain was achieved.In addition,the complex sedimentary stratigraphy of the paleo-Yangtze incised valley since the last glacial were investigated.We concluded that the basal MIS3 fluvial deposits might represent the earlier infilling over another incised valley,which might be formed during MIS4 although our

关 键 词：晚第四纪 长江三角洲地区 沉积环境演变 光释光年代 

分 类 号：P534.63[天文地球—第四纪地质学] P597.3[天文地球—古生物学与地层学]