Rhodoliths from the Cape Verde Archipelago: insights into climate change and megatsunami sediment dynamics

珊瑚红藻（红藻门）是整个新生代常见的碳酸盐生产者，特别是在非礁环境中，如佛得角群岛。与大多数其他藻类不同，珊瑚也能够在软或硬的地面上形成独立的结节，称为红柱石。这些蔷薇辉石在波浪和风暴的作用下被改造成离岸的其他环境，甚至在岸上的海滩上，在那里它们可以形成显著的堆积。在佛得角群岛，这样的红柱石积累沿着海岸线是已知的，从至少三个时间间隔，即（1）间冰期MIS 5e（约。距今12万年;（2）末次冰期。距今73000年，以及（3）现代海滩沉积。这些堆积物形成的一个关键时期是第二个时期，因为它与佛得角群岛之一福戈火山侧翼坍塌形成的海啸沉积物有关。拟议项目将研究这三个区间的红柱石以及相关的海洋阶地和海啸沉积物。中心目标是利用佛得角较新的地质记录，提高我们对冰川期和间冰期期间无礁热带岛屿大陆架环境中的红层及其物种组成的科学认识。该项目的另一个目的是调查海啸事件期间的红柱石迁移和沉积，作为正在进行的海啸研究的一个补充、非重叠的组成部分。首先，我们将在野外研究红柱石形成的沉积学背景，并采取代表性样品进行实验室分析。我们将制作岩石薄片，以便识别藻类类群和相关生物群，以及研究生长形式，埋藏学和相关沉积物的微相分析。有了这些知识，我们就可以重建红柱石体的形成过程以及相关的海啸沉积物。

Coralline red algae (Rhodophyta) are common carbonate producers throughout the Cenozoic time, especially in non-reefal environments, such as the Cape Verde Islands. Unlike most other algae, corallines are also capable of forming unattached nodules lying on soft or hard grounds, known as rhodoliths. These rhodoliths are reworked by wave and storm action into other environments offshore, or even onshore onto the beach, where they can form remarkable accumulations. On the Cape Verde Islands, such rhodolith accumulations along the coastline are known from at least three time intervals, namely (1) the interglacial MIS5e (ca. 120.000 years before present), (2) the last glacial period at ca. 73.000 years b.p., as well as (3) present-day beach deposits. A crucial interval for the formation of these accumulations is the second mentioned, because it is related to tsunami deposits formed by a flank collapse of Fogo volcano, one of the Cape Verde Islands. Rhodoliths from these three intervals as well as the associated marine terraces and tsunami deposits will be studied in the proposed project. The central aim is to use the younger geological record of Cape Verde to improve our scientific understanding of rhodolith beds and their species composition in a non-reefal tropical island shelf environment, both during a glacial and an interglacial period. The project also aims to investigate rhodolith transport and deposition during tsunami events, as a complementary, non-overlapping component of ongoing tsunami research. First of all, we will study the sedimentological background of rhodolith formation in the field and take representative samples that will be analyzed in the lab. We will make petrographic thin sections that allow the identification of algal taxa and associated biota, as well as the study of growth-forms, taphonomy, and the microfacies analysis of associated sediments. With this knowledge, we can reconstruct the formation of the rhodolith bodies as well as the associated tsunami deposits.