Rapid post-rift tectonic subsidence events in the Pearl River Mouth Basin, northern South China Sea margin
Rapid post-rift tectonic subsidence events in the Pearl River Mouth Basin, northern South China Sea margin
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南海北部珠江口盆地裂谷后快速构造沉降事件
DOI：
10.1016/j.jseaes.2017.07.024
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发表时间：
2017-10-01
影响因子：
3
通讯作者：
Huang, Ke
中科院分区：
文献类型：
--
作者：
He, Min;Zhong, Guangfa;Huang, Ke
综合26口钻井威尔斯和27条区域地震剖面资料，采用传统的一维回剥技术，对南海北方珠江口盆地中东部裂后沉降的时间、阶段和成因进行了研究。与以往盆地构造沉降回剥研究不同的是，本文利用新近建立的局部孔隙度-深度关系解压缩和更新的沉积学和古生物学资料重建古水深，计算了盆地构造沉降。基于井数据的沉降曲线显示了大致衰减模式的幅度和速度的裂谷后沉降在PRBs，这是根据一般的热沉降的典型的被动边缘的下降趋势。两次裂谷后快速构造沉降事件分别发生在中新世早期至中中新世早期和上新世。第一次快速裂谷后沉降事件的发生时间各不相同，盆地南部比北方更早。盆地南部同期构造沉降幅度较大。第二次构造快速沉降事件在盆地南北北方同时发生，南部沉降幅度较大。第一次快速沉降事件发生在渐新世至早中新世之间，与南海扩张脊的南跳有关;第二次快速沉降事件发生在晚中新世末期以来，与台湾的弧陆碰撞有关。深水斜坡区南部的PRBs在两次事件中的构造沉降幅度都比陆架区北方的PRBs大得多，这可能与其岩石圈薄得多有关。后者可能导致致密的下地壳和上地幔物质的上隆，从而导致更快速的构造沉降在南部的PRMB。
Data from 26 drill wells and 27 regional seismic profiles were integrated to investigate the timing, phase and origin of the post-rift subsidence in the middle to eastern Pearl River Mouth Basin (PRMB) of the northern South China Sea using the traditional 1-D backstripping technique. Different from previous research of backstripped tectonic subsidence in the basin, we calculated the tectonic subsidence using the newly built local porosity-depth relationships for decompaction and updated sedimentological and paleontological data for paleobathymetry reconstruction. Well-data based subsidence curves reveal a roughly decaying pattern in both the magnitude and rate of the post-rift subsidence in the PRMB, which is in accordance with the general decreasing trend of the thermal subsidence typical of a passive margin. Two events of rapid post-rift tectonic subsidence were identified, which occurred in the Early to early Middle Miocene and the Pliocene. The timing of the first rapid post-rift subsidence event varies and is earlier in the southern rather than northern part of the basin. Additionally, the amplitude of contemporaneous tectonic subsidence is greater in the southern part of the basin. The second rapid tectonic subsidence event occurred simultaneously in both the southern and northern parts of the basin, with the amplitude of subsidence being much greater in the southern part. We associate the first rapid subsidence event with the southward jump of the South China Sea spreading ridge, which occurred between the Oligocene and Early Miocene, while the second event with the arc-continent collision at Taiwan since the latest Late Miocene. The southern PRMB in the deep-water slope area shows a much higher magnitude of tectonic subsidence in both events than its northern counterpart in the shelf area, which could be associated with its much thinner lithosphere. The latter could cause upswelling of denser lower crust and upper mantle material, resulting in more rapid tectonic subsidence in the southern PRMB.