How the Yangtze delta responds to riverine sediment decline has become a hot research topic and an urgent issue to be addressed, especially after the impoundment of the Three Gorges Dam in 2003. This study investigated sedimentary features through the sediment granularity of surficial samples and short cores over the entire Yangtze subaqueous delta, aiming to better understand the spatial response of the subaqueous delta to sediment supply decline and local hydrodynamic adjustment of the estuary. The results show that four sedimentary zones of estuarine sand bar (Zone I), prodelta (Zone II), delta-shelf transition zone (Zone III) and residual sand (Zone IV) are distributed from the estuary to the shelf, characterised by first fining from zone I to zone II, and then coarsening from zone II to zone IV on grain size of surficial sediments. In the past few hundred years, the subaqueous delta has been generally prograded seaward following this sedimentary system spatially, manifested by generally fining upwards in the cores of the main subaqueous delta. However, sediment coarsening occurs on the top of the cores in the delta-shelf transition zone (Zone III), implying a recent retrogradation process. Based on the results of ²¹⁰Pb and ¹³⁷Cs, the sedimentary transition from progradation to retrogradation occurred since 1950s and was intensified after 1980s in the north part of Zone III, mainly caused by channel shrinking of the North Branch and riverine sediment decline. Comparatively, such a sedimentary transition is not significant in the south part of Zone III. But it is worth noting that surficial coarsening in the core (of the south part of Zone III) is probably related to drastic sediment decline since 2003 when the Three-Gorges Dam closed, which means that the Yangtze subaqueous delta has probably been in a full sedimentary transition. The sedimentary transition of the north subaqueous delta can provide an insightful reference for the sedimentary response of the Yangtze delta to further decline of sediment supply in the future.

长江三角洲对河流沉积物减少的响应已成为研究的热点和紧迫问题，尤其是在2003年三峡大坝蓄水之后。该研究通过地表样品和短岩心的沉积粒度研究了沉积特征。旨在更好地了解整个长江水下三角洲对沉积物供应下降和河口局部水动力调整的空间响应。结果表明，河口沙洲（Ⅰ区），三角洲（Ⅱ区），三角洲-陆架过渡带（Ⅲ区）和残留砂（Ⅳ区）四个沉积区从河口分布到陆架，其特征为：从I区到II区进行细化，然后从II区到IV区对表层沉积物的粒度进行粗化。在过去的几百年中，水下三角洲通常在空间上跟随该沉积系统向海推进，表现为在主要水下三角洲的岩心中总体向上细化。但是，在三角洲-陆架过渡带（III区）的岩心顶部会发生沉积物粗化，这意味着最近的回生过程。根据结果²¹⁰ Pb和¹³⁷Cs，沉积物从渐进到退化的过渡始于1950年代，并在1980年代后在III区北部加剧，这主要是由于北分支的河道收缩和河流沉积物减少所致。相比之下，这种沉积过渡在III区的南部并不重要。但是，值得注意的是，自2003年三峡大坝关闭以来，（III区南部）地心的表面粗化可能与沉积物的急剧减少有关，这意味着长江水下三角洲可能已经处于一个完整的时期。沉积过渡。北部水下三角洲的沉积过渡可以为长江三角洲未来对沉积物供应的进一步减少的沉积响应提供深刻的参考。