Turbidity currents can be characterized as net-erosive, net-depositional or net-bypassing. Whether a flow is erosive, depositional or bypasses depends on the flow velocity, concentration and size but these can also be impacted by external controls such as the degree of confinement, slope gradient and substrate type and erodibility. Our understanding of the relative importance of these controls comes from laboratory experiments and numerical modelling, as well as from field data due to the proliferation of high-resolution 3D seismic and bathymetric data, as well as the outcrop and rock record. In this study, based on extensive multibeam and seismic reflection surveys in combination with International Ocean Discovery Program cores from the South China Sea, we document a new mechanism of turbidity current transformation from depositional to erosive resulting in channel incision. We show how confinement by seamounts and bedrock highs of previously unconfined turbidity currents has resulted in the development of seafloor channels. These channels are inferred to be the result of confinement of flows, which have traversed the abyssal plain, leading to flow acceleration allowing them to erode the seafloor substrate. This interpretation is further supported by the coarsening of flow deposits within the area of the seamounts, indicating that confinement has increased flow competency, allowing turbidity currents to carry larger volumes of coarse sediment which has been deposited in this region. This basin-scale depositional pattern suggests that pre-established basin topography can have an important control on sedimentation which can impact characteristics such as potential hydrocarbon storage.

浊流可以表征为净侵蚀性、净沉积性或净旁路。流动是侵蚀性、沉积性还是旁路取决于流速、浓度和大小，但这些也可能受到外部控制的影响，例如限制程度、坡度梯度和基质类型和可蚀性。我们对这些控制的相对重要性的理解来自实验室实验和数值建模，以及由于高分辨率 3D 地震和测深数据以及露头和岩石记录的激增而产生的现场数据。在这项研究中，基于广泛的多波束和地震反射勘测，并结合来自南海的国际海洋发现计划核心，我们记录了从沉积到侵蚀导致通道切口的浊流转换的新机制。我们展示了海山和基岩高处对以前不受限制的浊流的限制如何导致海底通道的发展。这些通道被推断是流动限制的结果，这些流动已经穿过深海平原，导致流动加速，使它们能够侵蚀海底基底。海山区域内流动沉积物的粗化进一步支持了这一解释，这表明限制增加了流动能力，允许浊流携带大量沉积在该地区的粗沉积物。