Abstract Continental margins usually display along-strike morphological variation, with diverse underlying controls around the world. Based on 3D seismic data from the Baiyun Sag, northern South China Sea, this work provides a new case study to understand the combined controls on along-strike morphological variation over short strike distances. The northern slope of the Baiyun sag was characterized by a gently dipping ramp at the beginning of the Quaternary, and the Quaternary along-strike morphological variation in this area is mainly displayed in the deltas, submarine canyons and contourite depositional system. The deltas were featured by lobate form and mainly distributed at the western area, with shoreline parallel and oblique to the ramp strike in the west and east, respectively. The scales of the deltas and the associated submarine canyons decreased towards the east. The eastern plastered contourite drifts have a greater areal extent than those in the west, and the former are terraced. The Quaternary slope evolution took place in three stages (stage 1–3), of which the time intervals are ca. 2.6 - ca. 1.6 Ma, ca. 1.6 - ca. 0.14 Ma and ca. 0.14–0 Ma, respectively. The slope was characterized by a gentle ramp, deltas and contourites from stage 1–3 respectively. The along-strike morphological variation of the northern slope of the Baiyun Sag was predominantly influenced by the interplays between the deltas, pre-existing morphology, and oceanographic regimes. The localization of the lobate-form deltas with respect to the pre-existing submarine canyons on the ramp exerted a great influence on the along-strike variation of these canyons within stage 2. The interplay between the delta morphology (i.e., delta position and delta-front gradients) and the oceanographic regimes (i.e. contour currents and internal waves) controlled the along-strike variation in contourite processes during the stage 3. This study provides a new insight into the combination of controls responsible for along-strike morphological variation of post-rift continental margins evolving from a ramp. The underlying depositional processes revealed by this study would be helpful for understanding the lateral variability of sequence architectures and the deep-water sands deposition, which are important basis for guiding future deep-water hydrocarbon exploration on such continental margins elsewhere.

中文翻译：

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南海白云凹陷沿走第四纪形态变化：三角洲、先存形态和海洋过程之间的相互作用

摘要 大陆边缘通常表现出沿走向的形态变化，在世界范围内具有不同的潜在控制。基于南海北部白云凹陷的 3D 地震数据，这项工作提供了一个新的案例研究，以了解短走向距离内沿走向形态变化的综合控制。白云凹陷北坡在第四纪初期以缓倾斜坡为特征，该区第四纪沿走向形态变化主要表现在三角洲、海底峡谷和等高岩沉积体系中。三角洲呈叶状，主要分布在西部，西部和东部海岸线分别与斜坡走向平行和倾斜。三角洲和相关的海底峡谷的规模向东减小。东部抹灰等高岩流域面积大于西部，前者为阶地。第四纪斜坡演化发生在三个阶段（阶段 1-3），其中的时间间隔约为 2.6 - 约 1.6 马，约 1.6 - 约 0.14 毫安和大约 分别为 0.14–0 Ma。斜坡的特点是缓坡、三角洲和等高岩分别来自第 1-3 阶段。白云凹陷北坡沿走向形态变化主要受三角洲、先存形态和海洋状况相互作用的影响。叶状三角洲相对于斜坡上原有海底峡谷的定位对这些峡谷在第二阶段的沿走向变化产生了很大影响。 三角洲形态（即三角洲位置和三角洲）之间的相互作用-前沿梯度）和海洋状况（即等高线流和内波）控制了第 3 阶段等高线过程的沿走向变化。这项研究提供了对负责后沿走向形态变化的控制组合的新见解-从斜坡演变而来的裂谷大陆边缘。本研究揭示的潜在沉积过程将有助于理解层序构造的横向变异性和深水砂岩沉积，