Drowning unconformities are surfaces characterized on seismic data by high amplitude contrast between deepwater and shallow water facies. Such surfaces are created by the covering of the platform by onlapping siliciclastic sediments or other non-platform material. The key aspect of this paper is the application of the drowning unconformity concept, commonly used in marine settings, to a more restrictive one: the coquinas of the Itapema Formation, in the pre-salt succession of the Santos Basin (Brazil). In the studied area the sequence boundaries of the deposits related to the Itapema Formation are often associated with high reflectivity seismic horizons, which are tied to radioactive peaks of low-energy sedimentary facies in the gamma ray logs and also to the siliciclastic supply rate increase. However, the stratigraphic significance of these reflectors still lacks further investigation and an adequate description. In this way, it is proposed that the space-time filling of the Itapema Formation occurred by the successive migration of proximal facies towards the structural highs, under continuous accommodation space generation conditions and high carbonate production rate, with the depocenters limited by rapid expansions of the basin. The results presented here, therefore, suggest that the sedimentary record of this section was punctuated by instantaneous transgressive surfaces that altered the ecological accommodation, forcing the backstepping of the coquina deposits and the development of a drowning unconformity in the final stage of the Itapema Formation deposition. This configuration produced at the top of this unit a specific facies association characterized by packstones and mudstones composed of micritized grains, which increase in volume and thickness towards the structural lows and tend to be thinner on the way up to the structural highs, where they may be eroded by the Pre-Alagoas Unconformity. The correct identification of such surfaces is essential for understanding the sedimentary filling of the studied area. Depending on which surface is mapped, they may be related to different processes and occur in opposite positions in the base-level cycles. Thus, we propose the existence of two surfaces at the end of the deposition of the Itapema Formation. The first limits the top of the coquinas and is represented by the contrast of low-energy sediments (packstones and micritized mudstones) and the coquinas deposits, configuring the platform drowning itself. The second one, in turn, is understood here as the Pre-Alagoas Unconformity, a subaerial unconformity associated with the regional platform exposure, developed after the drowning events recognized here.

淹没不整合面是在地震数据上以深水相和浅水相之间的高振幅对比为特征的表面。这种表面是通过覆盖硅质碎屑沉积物或其他非平台材料而形成的平台。本文的关键方面是将海洋环境中常用的淹没不整合面概念应用于更具限制性的概念：Itapema 组的 coquinas，位于桑托斯盆地（巴西）的盐下层序中。在研究区域，与 Itapema 组相关的沉积物的层序边界通常与高反射率地震层相关，这与伽马射线测井中低能沉积相的放射性峰值以及硅质碎屑供应率增加有关。然而，这些反射体的地层意义仍然缺乏进一步的调查和充分的描述。这样，在连续的容纳空间生成条件和高碳酸盐产量条件下，Itapema 组的时空充填是由于近相连续向构造高位迁移而发生的，沉积中心受到快速扩张的限制。盆地。因此，此处提供的结果表明，该部分的沉积记录被瞬时海侵表面打断，改变了生态适应，迫使 coquina 沉积物后退，并在 Itapema 组沉积的最后阶段发展了淹没不整合面. 这种构造在该单元的顶部产生了一种特定的相组合，其特征是由微晶化颗粒组成的泥岩和泥岩，它们的体积和厚度向构造低处增加，在上升到构造高处时趋于变薄，在那里它们可能被前阿拉戈斯不整合面侵蚀。正确识别此类表面对于了解研究区域的沉积充填至关重要。根据映射的表面，它们可能与不同的过程有关，并发生在基础水平循环中的相反位置。因此，我们提出在 Itapema 组沉积结束时存在两个表面。第一个限制了 coquinas 的顶部，以低能量沉积物（灰岩和微晶化泥岩）和 coquinas 沉积物的对比为代表，构成了平台自沉。反过来，第二个在这里被理解为前阿拉戈斯不整合面，这是一种与区域平台暴露相关的地下不整合面，是在此处确认的溺水事件之后形成的。