Mixed Carbonate-Siliciclastic Deposits in a Channel Complex in the Northern South China Sea
Mixed Carbonate-Siliciclastic Deposits in a Channel Complex in the Northern South China Sea
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DOI：
10.1007/s12583-018-0830-4
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发表时间：
2018-06
影响因子：
3.3
通讯作者：
Benjun Ma;Shiguo Wu;Lijun Mi;T. Lüdmann;Jinwei Gao;Wei Gao
中科院分区：
文献类型：
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作者：
Benjun Ma;Shiguo Wu;Lijun Mi;T. Lüdmann;Jinwei Gao;Wei Gao
南海北坡海底通道复合体高分辨率三维地震资料新图像。复杂的河道绵延数百公里，穿过斜坡，从硅质大陆架边缘流入深海，将浅海环境与远洋平原连接起来。河道复合体的演化经历了两个沉积阶段：第一阶段（19.1 ~ 18.5 Ma）和第二阶段（18.5 ~ 17.5 Ma），以侵蚀面为分隔。在第一阶段，杂岩被纯硅质碎屑沉积物填满，形成厚块状砂岩，夹层为薄层泥岩。在第二阶段，河道复合体经历了5次碳酸盐-硅屑旋回沉积。出乎意料的河道填充碳酸盐沉积物呈现出异域特征，表明硅质碎屑河道出人意料地用于从邻近的浅海碳酸盐台地输送碳酸盐沉积物。通过分析硅质碎屑河道杂岩中碳酸盐的周期性沉积过程，推测其与浅海碳酸盐台地的硅碳酸盐生成有关，且极有可能受相对海平面变化的控制。与线源碳酸盐坡缘或小型碳酸盐河道不同，大型硅质碎屑河道复体将浅海碳酸盐台地与深水盆地直接连接起来，可在短时间内将大量浅海碳酸盐输送到远洋环境。这些新发现有助于更准确地估计浅海陆架和碳酸盐台地对深水斜坡的贡献。该研究表明，河道系统比预期的更为复杂，对描述深水沉积理论的概念模型具有重要意义。
New high-resolution 3D seismic data image a submarine channel complex in the northern slope of the South China Sea. The channel complex stretches hundreds of kilometers across the slope and flows into the deepsea from the siliciclastic shelf margin, linking neritic environment to the pelagic plain. The evolution of the channel complex developed two sedimentary stages, stage I (19.1–18.5 Ma) and stage II (18.5–17.5 Ma), separated by erosional surfaces. In the first stage, the complex was filled with pure siliciclastic sediments, forming thick-massive sandstone intercalated by thin layers of mudstone. During the stage II, the channel complex was deposited five carbonate-siliciclastic cycles. The unexpected channel-fill carbonate deposits present allochthonous characteristics, suggesting the siliciclastic channel was surprisingly used to transport carbonate sediment from the adjacent neritic carbonate platform. By analyzing the periodical carbonate sedimentary process in the siliciclastic channel complex, we infer that it was related to thein situcarbonate production of the neritic carbonate platform and was most likely to be controlled by the relative sea-level changes. Unlike line-source carbonate slope aprons or small-sized carbonate channels, the large-sized siliciclastic channel complex links directly neritic carbonate platform to deepwater basin and can transport large volumes of neritic carbonates to the pelagic environment in a short period. The new findings help to estimate the contributions of neritic siliciclastic shelf and carbonate platform to deepwater slope more accurately. This study suggests that channel systems are more complex than expected and have significant implications on the conceptual models describing the deepwater sedimentary theory.