| CHEN Shuhui,QIAO Peijun,ZHANG Houhe,XIE Xiaojun,CUI Yuchi,SHAO Lei. 2018. Geochemical characteristics of Oligocene-Miocene sediments from the deepwater area of the northern South China Sea and their provenance implications. Acta Oceanologica Sinica, 37(2):35－43 |
| Geochemical characteristics of Oligocene-Miocene sediments from the deepwater area of the northern South China Sea and their provenance implications |
| 南海北部深水区渐新-中新世沉积地球化学特征及物源演变 |
| Received:May 22, 2017 Revised:October 11, 2011 |
| DOI：10.1007/s13131-017-1127-7 |
| Key words:geochemistry zircon U-Pb age provenance South China Sea Baiyun deepwater area |
| 中文关键词: 地球化学 碎屑锆石U-Pb定年 物源 南海 白云深水区 |
| 基金项目:The National Natural Science Foundation of China under contract Nos 41576059, 91128207 and 91528302; the National Major Science and Technology Projects under contract No. 2011ZX05025-006-02. |
| Author Name | Affiliation | E-mail | | CHEN Shuhui | State Key Laboratory of Marine Geology, Tongji University, Shanghai 200092, China
Shenzhen Branch of China National Offshore Oil Corporation, Guangzhou 510240, China | | | QIAO Peijun | State Key Laboratory of Marine Geology, Tongji University, Shanghai 200092, China | qiaopeijun@tongji.edu.cn | | ZHANG Houhe | China National Offshore Oil Corporation Research Institute, Beijing 100027, China | | | XIE Xiaojun | China National Offshore Oil Corporation Research Institute, Beijing 100027, China | | | CUI Yuchi | State Key Laboratory of Marine Geology, Tongji University, Shanghai 200092, China | | | SHAO Lei | State Key Laboratory of Marine Geology, Tongji University, Shanghai 200092, China | |
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| Abstract: |
| Geochemical and detrital zircon U-Pb dating data for drilled sediments from the Baiyun deepwater area of the northern South China Sea demonstrate a change of sedimentary sources from the Oligocene to the Miocene. Zircon ages of the pre-rift Eocene sequences are dominated by Yanshanian ages with various peak values (110-115 Ma for U1435 and L21; 150 Ma for H1), indicating local sediment supply from the pre-existing Mesozoic magmatic belt. For the Oligocene sediments in the northern part of the basin, the rare earth elements show different distribution characteristics, indicating sediment supply from the paleo-Zhujiang River (Pearl River), as also confirmed by the multimodal zircon age spectra of the Lower Oligocene strata in Well X28. By contrast, a positive Eu anomaly characterizes sediments from the western and southern parts of the basin, indicating potential provenances from intermediate to basic volcanic rock materials. The Baiyun Movement at the end of the Oligocene contributed to a large-scale subsidence in the deepwater area and also a northward retreat of continental shelf break, leading to deepening depositional environment in the basin. As a result, all the detrital zircon ages of the Upper Oligocene strata from Wells X28, L13, and L21 share a similar distribution, implying the possible control of a common source like the Zhujiang River. During the Miocene, whereas sediments in the northern area were mainly sourced from the Zhujiang River Delta, and those in the southern deepwater area continued to be affected by basic volcanic activities, the Dongsha Uplift could have contributed as the main source to the eastern area. |
| 中文摘要: |
| 地球化学及碎屑锆石U-Pb定年结果显示，南海北部白云凹陷深水区曾于渐新世至中新世发生沉积物源转变。U1435、L21及H1井始新世锆石年龄频谱以燕山期为主，指示该时期盆地大部分主要受中生代局部物源影响。至早渐新世，稀土配分结果及X28井相对复杂的多峰特征均反映古珠江开始为盆地北部提供沉积物。与此相反，盆地西部及南部以Eu元素正异常为主，表明主要受中-基性源区影响。晚渐新世白云运动导致白云凹陷发生强烈热沉降，陆架坡折带也由凹陷南侧突变式地跳跃至北侧，该地区整体进入陆坡深水环境。该构造事件造成南海北部深水区沉积物源发生重大转变，珠江影响进一步扩大，使得X28、L13及L21井均呈现相似的锆石年龄频谱特征。中新世白云凹陷北部地区主要受控于珠江物源，南部地区继续接受基性沉积物供给，而东部地区则主要受到东沙隆起的持续影响。 |
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