The purpose of this paper is to analyze the morphology of the Quaternary relict features and bedforms that characterize the outer zone of an extensive mesomareal system, which is part of the Bahía Blanca estuary (Argentina), and to estimate the prevailing hydro-sedimentological conditions on the continental shelf adjacent to the estuary. Surveys with a multibeam bathymetric system, side-scan sonar and a high-resolution seismic system (3.5 kHz) were carried out and bottom sediment samples were collected. In general, the seafloor presents a varied configuration, marked by changes in its physiography. The Quaternary relict features are composed of two terraces (12–14 m and 18–22 m deep), with steeply sloping escarpments, that are oriented approximately parallel to the current coastline. Associated with these terraces, wide abrasion platforms develop with irregular and plateau-like structures up to 4 m high, together with large rocky blocks up to 6 m in diameter. Here, the predominant sediment corresponds to a gravel-sized material composed of quartzite boulders, siltstone fragments of up to 7 cm, and biogenic remains with different degrees of fragmentation. These sedimentological data, together with the bathymetric and seismostratigraphic information, indicate that the terraces and abrasion platforms are ancient shorelines that originated in an environment with high wave energy, corresponding to periods of stabilization of sea level rise during the final stage of the last postglacial transgression (late Pleistocene-Early Holocene). On the other hand, asymmetric dunes of different sizes (0.5 m < height < 5 m, 5 m < wavelength < 200 m), sand ribbons (length > 300 m) and comet marks originated in equilibrium with the present-day hydro-sedimentological conditions. The availability of sandy material mobilized as bedload is the determining factor for the generation of the varied bedforms. Thus, sand ribbons and comet marks are generated especially in the northern sector of the area, with mobile sediment thicknesses ≤ 0.5 m. With larger thicknesses the formation of dunes occurs. Their size and asymmetry show an intense transport of sand as bedload towards the continental shelf, the southern sector of the area being the main route of the sediment that leaves the estuary. This sediment is the supply source of the sandy shoals that are part of the great ebb delta developed on the continental shelf in the external area of the Bahía Blanca estuary.

本文的目的是分析第四纪遗迹特征和床型的形态，这些特征和床型表征了一个广泛的中界系统的外部区域，该系统是 Bahía Blanca河口（阿根廷）的一部分，并估计了当时盛行的水文沉积条件。靠近河口的大陆架。使用多波束测深系统、侧扫声纳和高分辨率地震系统（3.5 kHz）进行了调查，并收集了底部沉积物样本。一般来说，海底呈现出多种多样的形态，其特点是其自然形态的变化。第四纪遗迹由两个阶地（12-14 m和18-22 m深）组成，坡度陡峭悬崖，其方向与当前海岸线大致平行。与这些阶地相关的宽磨损平台发育不规则的高原状结构，最高可达4 m，以及直径达6 m的大型岩石块。在这里，主要沉积物对应于砾石大小的物质，由石英岩巨石、长达 7 厘米的粉砂岩这些沉积学数据，连同测深和地震地层信息，表明阶地和磨损平台是古老的海岸线，起源于高波能环境，对应于海平面上升在最后一次冰河后海侵的最后阶段（更新世晚期-全新世早期）。另一方面，不同大小的不对称沙丘（0.5 m < 高度 < 5 m，5 m < 波长 < 200 m）、砂带（长度 > 300 m）和彗星痕迹起源于与现今水文沉积学的平衡。条件。作为床载动员的沙质材料的可用性是产生不同床形的决定因素。因此，沙带和彗星痕迹尤其在该地区的北部地区产生，移动沉积物厚度 ≤ 0.5 m。随着厚度的增加，会形成沙丘。它们的大小和不对称性表明沙子作为床载向大陆架的强烈运输，该地区的南部是离开河口的沉积物的主要路线。这种沉积物是沙质浅滩的供应来源，沙质浅滩是在 Bahía Blanca 河口外围大陆架上发育的大退潮三角洲的一部分。