珠江口盆地白云凹陷中新世水道发育的主控因素

珠江口盆地白云凹陷在中新世21~18.5 Ma、13.8~12.5 Ma和10.5~8.5 Ma三个时期均发育有大型水道。不同时期水道的形态和内部结构均不相同。21~18.5 Ma时期水道内部结构简单，水道延伸距离远，搬运的沉积物在白云凹陷远端沉积下来；13.8~12.5 Ma水道逐渐向北退却迁移，早期水道在凹陷南部地区发育，随后逐渐向北溯源迁移。10.5~8.5 Ma水道逐渐变窄变深，具有典型汇聚水道的特点。上述水道迁移和形态特征的变化是由于各时期水道发育的控制因素不同造成的。21~18.5 Ma时期水道的发育与来自于陆架边缘三角洲的充足物源供给有关；13.8~12.5 Ma时期水道的主控因素是13.8 Ma时期海平面的大幅度下降；10.5~8.5 Ma水道的迁移与东沙运动造成白云凹陷相对隆升以及古地貌密切相关。对不同时期水道控制因素的分析为中新世以来白云凹陷水道的形态及演化过程分析提供了新的地质信息。

Controlling Factors on the Miocene Channel in Baiyun Sag,Pearl River Mouth Basin

During 21-18.5 Ma, 13.8-12.5 Ma and 10.5-8.5 Ma of Miocene, the channels developed in Baiyun Sag. In these three stages, the shape and architecture of the channels were different. During 21-18.5 Ma, the architecture of the channel was simple, the channel extended a long distance and the sediment was deposited in the distal end. In 13.8-12.5 Ma, the channel migrated northward. During the early of 13.8-12.5 Ma, the channel only developed in the south, then developed upstream. The channel in 10.5-8.5 Ma became deeper and narrower, and had the convergent feature. These changes of these channels’ migration and shape feature were due to different controlling factors in these stages. In 21-18.5 Ma, the channel was related to the abundant sediment supply from the shelf margin delta. In 13.8-12.5 Ma, the channel was affected by the significant sea-level decline in 13.8 Ma. In 10.5-8.5 Ma, Dongsha Movement led to the Baiyun Sag uplift and the paleo-topography determined the channel development. The analysis of the controlling factors in different stages provided new information to the research of the channel shape and evolution in each stage.