中国南海东沙隆起北缘晚始新世构造裂点迁移及其源-汇效应

Migration of the Late Eocene knickpoints and their source-to-sink system along the northern margin of the Dongsha Uplift， South China Sea

刘强虎 彭光荣 刘培 余雄飚 熊万林 周子强 朱红涛

Qianghu LIU Guangrong PENG Pei LIU Xiongbiao YU Wanlin XIONG Ziqiang ZHOU Hongtao ZHU

为验证超覆背景下的残余地貌能否为沉积物产出提供有效信息，以珠江口盆地内最大凸起单元——东沙隆起作为研究对象，应用全覆盖地震数据及钻井约束，提取了晚始新世恩平组残余地貌上关键流域的河道纵向剖面，刻画了边界断裂的活动性，量化了砂体粒度及沉积通量的时-空变化。研究评估了残余地貌特征与沉积区粒度和通量变化间的匹配程度。研究表明：两大关键流域的河道剖面均存在构造裂点，且与晚始新世活跃的边界断层相匹配。裂点溯源迁移时可能沟通了内流水系，与汇区粒度整体变细，通量变大规律一致。源区地貌特征和汇区沉积记录在地貌演化的视角下指示遭受后期改造较弱的残余地貌很可能仍然保存着深-时的源-汇信息。精细解剖残余地貌、源区地形坡度、基岩岩性与裂点迁移，有助于深-时源-汇系统不同期次重建及砂体性质与规模预测。

This study aims to verify whether remnant landscapes preserved by stratigraphic overlapping can provide useful insights into characterizing sediment production. Focusing on the Dongsha Uplift， the largest uplift unit in the Pearl River Mouth Basin （PRMB）， and using full-coverage seismic data and well constraints， we extract the longitudinal channel profiles of key catchments from the remnant landscapes of the Late Eocene Enping Formation， characterize the boundary fault activity and quantify the spatiotemporal variations in sand-body grain size and sediment flux. Furthermore， the correlation between the characteristics of remnant landscapes and variations in the grain size and sediment flux in the sedimentary areas is assessed. The results indicate that the observation of tectonic knickpoints in the channel profiles of the two key catchments is consistent with the activities of boundary faults during the Late Eocene. These knickpoints may have facilitated interconnections between closed drainage systems during their headward migration， leading to overall finer grain size and greater sediment flux as archived in the sink area. Importantly， our results illustrate that geomorphological features of the source area and sedimentary records of the sink area can be successfully reconciled in terms of landscape evolution； this implies that remnant landscapes with weak post-burial deformation still preserve deep-time source-to-sink information. The fine analysis of remnant landscapes， and detailed characterization of source area slope， bedrock lithology， and knickpoint migration contribute to the reconstruction of deep-time source-to-sink systems across different stages， as well as improvement of the predictions of sand-body properties and scales in the systems.

10.11743/ogg20250310