Through comprehensive seismic, stratigraphic, and sedimentological analysis, this paper describes the stratigraphic architecture of the late Quaternary sediments and depositional dynamics in a region ~ 3.5 km offshore of the current south-west Namibian coastline. The landscape evolution model of this area is based on 2D seismic reflection profiles calibrated to approximately 500 boreholes, which yielded sedimentary and seismic facies data of exceptionally high resolution. The data permitted the characterization of four sedimentary facies units and the reconstruction of the submerged landscape dominated by a barrier complex. We compare this barrier complex with the sediment bodies preserved along the adjacent coastline, and account for their geological evolution in response to late Quaternary relative sea-level fluctuations along the West Coast. The most noteworthy depositional units in the study area are the normal regressive coarse gravel beaches trending shore parallel, with the primary gravel barrier and its preserved coeval back-barrier deposits that exceed 7 km in length along the coast. Based on the radiocarbon dates from the rarely preserved early flooding facies (14.0 and 13.3 ka BP), the primary barrier complex formed during a stage of slowing rising relative sea-level subsequent to Meltwater Pulse 1A. Moreover, the barrier beach complex formed on a low-gradient palaeo-bathymetry slope that is punctuated by a break on its landward side (i.e., a regional knick point), which promoted the local accommodation of sediments. The preservation of the barrier beach complex and back-barrier deposits is attributed to rapid relative sea-level rise, linked to the early Holocene Meltwater Pulse 1B between ~ 11.5 and 11.2 ka BP, and an increase in back-barrier accommodation facilitated by the antecedent topography.

中文翻译：

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纳米比亚南部水下砾石屏障海滩复合体的晚第四纪沉积学历史

通过综合地震、地层学和沉积学分析，本文描述了纳米比亚当前西南海岸线近海约 3.5 公里区域晚第四纪沉积物的地层结构和沉积动力学。该地区的景观演化模型基于校准到约 500 个钻孔的二维地震反射剖面，产生了分辨率异常高的沉积和地震相数据。数据允许表征四个沉积相单元和重建由屏障复合体主导的水下景观。我们将这个屏障复合体与沿相邻海岸线保存的沉积体进行比较，并解释了它们响应西海岸晚第四纪相对海平面波动的地质演化。研究区最值得注意的沉积单元是与海岸平行的正常退行粗砾石滩，其主要砾石屏障及其沿海岸长度超过 7 公里的同时代后屏障沉积物保存完好。根据很少保存的早期洪水相（14.0 和 13.3 ka BP）的放射性碳数据，主要屏障复合体是在 Meltwater Pulse 1A 之后相对海平面上升减缓阶段形成的。此外，障滩复合体形成在一个低梯度的古测深斜坡上，在其陆地一侧（即区域性的裂缝点）被打断，这促进了沉积物的局部容纳。屏障海滩复合体和后屏障沉积物的保存归因于相对海平面的快速上升，