Volcano-sedimentary evolution of the Walvis Ridge (IODP Expedition 391)

沿沃尔维斯海脊(WR)的IODP 391探险将提供一个独特的机会，重建几个海底火山建筑的地质演化，这些海底火山建筑被认为是由于缓慢移动的大洋板块上的热点火山作用而形成的。在之前的钻探中发现了大量的火山碎屑沉积，表明自晚白垩世以来火山岛的反复形成。然而，我们对它们的形成和演化的理解仍然受到非常有限的钻探的阻碍。同样，全球被淹没的热点岛屿的长期地质(构造和侵蚀)演变仍然知之甚少，因为难以了解和描述其顶峰地质特征；因此，现有的海洋岛屿形成模型是基于对有限的空中火山建筑物的观察，这些建筑物比被认为代表古代海洋岛屿的大量未研究的海山要年轻和(或)大得多。拟议的研究将通过对将在391次探险期间从WR Guyot顶部恢复的火山沉积序列的岩相和地球化学特征来帮助解决这种观测偏差。这将使我们能够测试海脊的演化是否伴随着短暂海洋岛屿的形成，以及这些可能的岛屿的演化是否类似于大西洋和太平洋其他现代和古代热点板内火山的演化。最终，这将有助于开发一种改进的板内大型海洋火山形成和演化模型。

IODP Expedition 391 along the Walvis Ridge (WR) will provide a unique opportunity to reconstruct the geological evolution of several submarine volcanic edifices considered to have formed due to hotspot volcanism on a slow-moving ocean plate. Previous drilling of the WR during DSDP Legs 39, 40, 74 and 75 recovered a large diversity of volcaniclastic deposits that suggest recurring formation of volcanic islands since the Late Cretaceous. However, our understanding of their formation and evolution remains hampered by very limited drilling. Similarly, the long-term geological (constructional and erosional) evolution of drown hotspot islands globally is still poorly understood due to difficulties to access and characterise their summit geology; consequently, existing models of oceanic island formation are based on observations from a limited selection of subaerial volcanic edifices that are much younger and/or unusually large compared to the vast population of unstudied seamounts thought to represent ancient oceanic islands. The proposed research will help address this observational bias through a lithofacies and geochemical characterisation of volcano-sedimentary sequences to be retrieved during Expedition 391 from the top of WR guyots. This will allow to test whether the evolution of the Ridge was accompanied by the formation of ephemeral oceanic islands, and whether the evolution of these possible islands was similar to that of other modern and ancient hotspot intraplate volcanoes in the Atlantic and Pacific Oceans. Ultimately, this will help develop an improved model of formation and evolution of large intraplate oceanic volcanoes.