The inner shelf of Namibia’s southwestern coastline comprises the submerged extension of the world’s largest diamond placer deposit. The onshore raised beach deposits, which are constrained by wave-cut cliffs and platforms, bevelled into the schist bedrock during palaeo-sea level stillstands, are largely mined out. As land-based operations near their practical limit, spatially accurate resource estimation of the inner shelf becomes increasingly critical to extend the life of mine of this extensive but low-grade resource. This study analyses a comprehensive seismic-reflection dataset, to produce a 50-m cell size bedrock morphology surface for the inner shelf. The data reinforce previous results and show that inherited structural influence exerts the overarching control on bedrock morphology at the scale of the study area. However, within this framework, the detailed data have now facilitated the zonation of the study area into discrete structural zones from which subtle coast-parallel bedrock gradient changes, that we interpret to represent submerged palaeo-shoreline morphologies (i.e. bedrock gradient changes associated with wave-cut cliffs and platforms), have been extracted. These bedrock gradient variations are contextualised within areas of similar glacial isostatic adjustment (GIA) response, which lends weight to the GIS-based palaeo-shoreline interpretation. Although these may be considered composite features that are the product of 42 million years of shoreline transgression and regression, the more recent occupation of the shoreline at these depth intervals, during the late Pleistocene/Holocene, forms a critical upgrading component to the offshore resource. Our study proposes a − 20 msl shoreline, the most recent occupation of which we link to the peak of marine isotope stage (MIS) 5c, and a − 30 msl shoreline that is linked to the time shortly after MIS 5c and the peak of MIS 5a. The most recent period of shoreline occupation for the deepest shoreline at − 40 msl is attributed to slowly rising sea level between 10.8 and 10.6 ka. This information is critical to the development of the resource estimation philosophy for the offshore extension of mining operations.

纳米比亚西南海岸线的内陆架包括世界上最大的钻石砂矿床的水下延伸部分。陆上凸起的海滩沉积物受到波浪切割悬崖和平台的限制，在古海平面静止期间倾斜到片岩基岩中，大部分被开采出来。随着陆上作业接近其实际极限，内陆架的空间精确资源估计对于延长这种广泛但低品位资源的矿山寿命变得越来越重要。本研究分析了一个综合的地震反射数据集，为内陆架生成了一个 50 米单元大小的基岩形态表面。数据加强了先前的结果，并表明继承的结构影响对研究区规模的基岩形态施加了总体控制。然而，在这个框架内，详细的数据现在有助于将研究区划分为离散的结构带，从中微妙的海岸平行基岩梯度变化，我们解释为代表淹没的古海岸线形态（即与波切相关的基岩梯度变化）悬崖和平台），已被提取。这些基岩梯度变化与类似冰川均衡调整 (GIA) 响应的区域有关，这增加了基于 GIS 的古海岸线解释的权重。虽然这些可能被认为是 4200 万年海岸线海侵和回归的产物的复合特征，但在更新世晚期/全新世期间这些深度间隔的海岸线最近被占领，形成了近海资源的关键升级组成部分。我们的研究提出了 - 20 msl 海岸线，我们将其最近占用与海洋同位素阶段 (MIS) 5c 的峰值相关联，以及 - 30 msl 海岸线与 MIS 5c 和 MIS 峰值之后不久的时间相关联5a. 最深海岸线在 − 40 msl 处的最近海岸线占领归因于海平面在 10.8 至 10.6 ka 之间缓慢上升。该信息对于开发用于采矿作业的海上扩展的资源估计原理至关重要。最深海岸线在 − 40 msl 处的最近海岸线占领归因于海平面在 10.8 至 10.6 ka 之间缓慢上升。该信息对于开发用于采矿作业的海上扩展的资源估计原理至关重要。最深海岸线在 − 40 msl 处的最近海岸线占领归因于海平面在 10.8 至 10.6 ka 之间缓慢上升。该信息对于开发用于采矿作业的海上扩展的资源估计原理至关重要。