广东北江上游河流阶地与岩溶洞穴堆积物光释光年代及其地貌意义  

Luminescence dating of fluvial terrace and karst cave deposits in the Upper Beijiang River,Guangdong Province,and its geomorphological implications

作　　者：黄孝波 赵心宇 李宏卫 田若楠 胡昆 李燕文 涂华 赖忠平 HUANG Xiaobo;ZHAO Xinyu;LI Hongwei;TIAN Ruonan;HU Kun;LI Yanwen;TU Hua;LAI Zhongping(Guangdong Geological Survey Institute,Guangzhou,Guangdong 510080,China;Guangdong Provincial Key Laboratory of Marine Disaster Prediction and Prevention,Shantou University,Shantou 515063,China)

机构地区：[1]广东省地质调查院,广州510080 [2]汕头大学海洋灾害预警与防护广东省重点实验室,汕头515063

出　　处：《海洋地质与第四纪地质》2024年第6期186-194,共9页Marine Geology & Quaternary Geology

基　　金：广东省2021年度自然资源事务管理—生态林业建设专项资金项目“第四纪冰期旋回对南岭生物多样性影响调查研究”(2021GJGY001)。

摘　　要：河流阶地沉积和岩溶洞穴冲积物是记录河流下切历史的重要载体,但在流域尺度上多层溶洞的发育过程与河流下切过程的耦合关系仍缺乏直接的年代学证据。广东北江上游水系流经砂岩盆地和石灰岩区,流经区分别发育了多级河流阶地和多层洞穴系统,为探究河流与多层溶洞演化关系提供了理想条件。本文对北江上游坪石镇二级阶地和乐昌古佛岩第二层溶洞中的河流沉积物进行了石英光释光测年,结果表明前者至少形成于101~79 ka,后者至少形成于121~71 ka。二者均对应于深海氧同位素5阶段,指示该区洞穴冲积物和河流阶地沉积在冰期-间冰期尺度上是同步的。本文为研究北江上游喀斯特洞穴冲积物与河流阶地发育的耦合关系提供了放射性年代学证据,对利用流域内岩溶洞穴冲积物建立区域河流地貌演化和构造抬升历史提供了理论依据。Fluvial deposits in river terraces and alluvial deposits in karstic caves are important archives for geomorphological study of river valleys.However,there is still a lack of direct chronological evidence supporting the relationship between the developing processes of multilayer caves and river terraces in basin scale.The upper reaches of Beijiang River run through both sandstone basins and limestone areas,resulted in multilevel river terraces and cave systems.This unique setting provides an ideal opportunity to investigate the evolutionary relationship between rivers and stratified caves.In this study,optically stimulated luminescence(OSL)dating was applied to constrain the age of the fluvial deposits from the second-level terrace in Pingshi Town in the upper reaches of Beijiang River in Guangdong Province,as well as from alluvial sediments in the second-level karst cave of Gufoyan Cave system in the neighboring area.The dating results reveal that the second terrace at Pingshi dates back to 101~79 ka,while the deposits in the second layer of Gufoyan Cave date back to 121~71 ka,both falling within the Marine Isotope Stage(MIS)5.These findings indicate that during the last interglacial period,an incision occurred in the upper reach of the Beijiang River,leading to a drop in regional groundwater table.Therefore,it resulted in abandonment of the second layer of Gufoyan Cave by underground river.The cave alluvial sediments and river terrace deposits in the area were synchronous at the glacial-interglacial time scale,which provided direct chronological evidence for co-evolution between karst and river landforms in the upper reaches of Beijiang River.This study provided supports to further studies on regional Quaternary geology and river landform evolution through dating alluvial sediments found within karst caves.

关 键 词：河流阶地 喀斯特洞穴 光释光测年 北江 

分 类 号：P531[天文地球—古生物学与地层学]