In the context of rising sea levels, wave-dominated coasts and deltas are among the most threatened of coastal landforms. The study of submerged deltas, in tandem with other drowned wave-dominated shoreline sequences, can shed light on the long-term coastal behaviour of these threatened shorelines when subject to high-end scenarios of relative sea-level rise. Using ultra high-resolution seismic reflection data and gravity core samples, this paper investigates the post-glacial stratigraphic development and architecture of the shelf off southern Mozambique. We document several well-preserved beachrock/aeolianite palaeo-shoreline complexes from water depths of −100, −75 and −60 m, interpreted as representing the positions of former sea-level slowstands or stillstands. These overlie the regional subaerial unconformity associated with the last glacial maximum and are linked to two phases of deltaic deposition. Pro-deltaic deposits on the outer shelf were linked with the period of sea-level stability attributed to the −100 m shoreline, while proximal delta front deposits on the inner- to mid-shelf are linked to a slowstand evident in the local sea level record at −40 m. Well-developed lower delta plain facies overlie both shoreline and delta front facies and show evidence of strong channelisation during normal regression of the delta. These are overlain across the shelf by isolated and stranded pieces of the now relict shoreface, trapped to seaward by the shoreline complexes. The more proximal parts of the shelf are in turn overlain by fluvial-derived muddy facies of the current prodeltas of the area.

The preservation of shoreline and delta deposits was enhanced by intervening rapid increments in sea-level rise associated with meltwater pulses 1A (−100 m) and 1B,(−60 m) though the preservation of the −75 shoreline feature, in spite of modest rates of Older Dryas base-level change, points toward other factors such as rapid cementation as dominant in this instance. The region's high sediment supply exerted a primary control on shelf preservation by dampening the erosive extent of wave-ravinement. Variations in antecedent gradient are responsible for much of the documented along-shelf and down-dip depositional variability: low-gradient settings promoted the development of broad coastal plains and strongly wave-dominated deltaic facies, while steeper areas of the shelf favoured the development of coastal landforms in relatively narrow complexes fronted by deep-water deltaic deposits. Steeper areas of the shelf also tend be characterised by an embayed along-coast profile that locally mitigates wave-energy, reinforcing the influence of inherited gradient.

Once preserved, drowned coastal barriers introduced an additional geological control as post-glacial sediment became trapped between these features on the outer shelf. The dispersal of modern sediments is strongly influenced by the hydrodynamic regime Delagoa Bight, under which fluvial muds are transported northeastward along the shelf by a persistent inner-mid shelf counter-current. A considerable proportion of the modern sediment budget is lost off-shelf where the shelf narrows.

This study shows that low antecedent gradients foster gentle coastal profiles predisposed to delta overstepping. Though local topographic knickpoints can aid in preserving the delta during submergence, they do not buffer the delta from the general effects of inundation which include drowning of the delta top. Once overstepped, the former delta can be overlain by distal deltaic sediments associated with the higher sea level and associated fluvial and oceanographic forcing quite different from earlier phases of delta construction.

在海平面上升的背景下，以波浪为主的海岸和三角洲是沿海地貌最受威胁的地区之一。与其他淹没的波浪主导的海岸线序列一起进行的淹没三角洲研究可以揭示这些受威胁海岸线在长期相对海平面上升情况下的长期沿海行为。本文使用超高分辨率地震反射数据和重力岩心样本，研究了莫桑比克南部冰川后的地层发育和构造。我们从-100，-75和-60m的水深中记录了几个保存完好的滩石/风成岩古海岸线复合体，这些复合体被解释为代表了以前的海平面缓坡或静水的位置。这些覆盖了与最后一次冰川最大值相关的区域性地下不整合，并与三角洲沉积的两个阶段相关。外层架上的前三角洲沉积物与归因于-100 m海岸线的海平面稳定期有关，而内层至中层的近端三角洲前缘沉积物与当地海平面上明显的慢速台积有关。记录在−40 m。发达的下三角洲平原相覆盖在海岸线和三角洲前缘相上，显示出在三角洲正常消退期间强通道化的证据。这些被搁置在现在的遗迹岸壁上的零散而零散的部分覆盖在架子上，被海岸线综合体困在海面。架子的更近端部分又被该地区当前三角洲的河流相泥质相覆盖。

尽管保留了适度的-75海岸线特征，但通过保留-75海岸线特征，通过介入与融水脉冲1A（−100 m）和1B，（−60 m）相关的海平面上升的快速增加，加强了对海岸线和三角洲沉积物的保护。较早的树蛙基本水平的变化率，指向其他因素，例如在这种情况下占主导地位的快速胶结。该地区大量的泥沙供应通过抑制波浪起伏的侵蚀程度，对架子的保存起到了主要控制作用。前期梯度的变化是造成大量记录的陆架和下倾沉积变化的原因：低梯度环境促进了宽阔的沿海平原和以波浪为主的三角洲相的发展，而较陡的陆架区域则有利于在较深的三角洲沉积物所面对的相对狭窄的综合体中发展沿海地貌。架子的更陡峭的区域也往往具有沿海岸轮廓的嵌套特征，该轮廓局部减轻了波能，从而增强了继承梯度的影响。

一旦被保存，淹没的沿海壁垒引入了额外的地质控制，因为冰期后的沉积物被困在外层架的这些特征之间。现代沉积物的扩散受到流体动力机制Delagoa Bight的强烈影响，在这种情况下，河流泥浆通过持续的中－中层架逆流沿架子向东北方向运输。在架子狭窄的地方，现代泥沙预算中有相当一部分流失在现成的地方。

这项研究表明，较低的前斜坡会促进平缓的沿海剖面，从而容易造成三角洲超采。尽管局部地形拐点可以在淹没期间帮助保留三角洲，但它们并不能从淹没包括淹没三角洲顶部的一般影响中缓冲三角洲。一旦被超越，先前的三角洲就可能被远端的三角洲沉积物所覆盖，这些沉积物与较高的​​海平面以及相关的河流和海洋学强迫作用与三角洲建设的早期阶段大不相同。