Indian Ocean Carbonate Platform Evolution: Currents, Monsoon, and Sea Level (IndoCarb)

这项提议的首要目标是解锁马尔代夫的新近系古海洋、海平面和古环境档案。需要检验的假设是，古海洋变化是碳酸盐台地相和地层的主要控制因素。因此，马尔代夫碳酸盐台地将被开发为根据海平面和古海洋学变化对台地开发进行双重控制的参考案例。这一目标将通过分析IODP探险359期间获得的岩心、沉积物样品和电缆测井，并将这些数据与地震地层学联系起来来实现。马尔代夫碳酸盐平台的地层演化被几个反映平台架构变化的关键区间所打断。不同的事件是(A)渐新世台地的淹没和后来在中新世的受限环境的发展(溺水1)，(B)中中新世台地边缘从岸缘到具有悬肩的台地的重组(悬肩)和(C)中中新世从台地到漂流沉积的周转(溺水2)。这些事件与全球海平面之间的联系是模棱两可的，表明海平面波动并不是这种模式的唯一驱动因素。溺水1中断了渐新世台地的生长，但使台地在中新世恢复到更边缘的位置。这一溺水事件的控制因素尚不清楚，但可能与海平面波动和有机物含量上升有关。溺水2与印度洋季风爆发导致的强流发生有关。大部分银行的倒闭是循序渐进的，也是永久性的。另一个重大事件是，中中新世从岸边台地到悬肩台地的变化与中新世气候最佳时期的开始有关。与台地边缘和斜坡几何学的变化同步，盆地发生了重大的重构，记录在沉积物中，遗迹组构和微相发生了剧烈变化。对遗迹组构、微相、XRF数据、电缆测井和地震剖面的综合研究将能够区分环境条件，并将它们与影响碳酸盐台地的过程联系起来。我们的目标还是证明，存在影响碳酸盐平台的不同类型的溺水；其中一些以一种可逆的方式中断了平台的发展，使沉积环境得以再生，而另一些则是完全不可逆转的，永久地改变了沉积环境。工作假说是，不仅营养物质的输入，而且洋流的强度对平台的重新配置也有贡献。这些结果远远落后于对区域沉积学的理解，并对碳酸盐沉积学模型产生了总体影响。

The overarching objective of this proposal is to unlock the Neogene paleoceanographic, sea-level and paleoenvironmental archive of the Maldives. The hypothesis to test is that paleoceanographical changes are a major controlling factor of carbonate platform facies and stratigraphy. Therefore the Maldives carbonate platform will be developed as a reference case of a dual control on platform development by sea-level and paleoceanographical changes. This goal will be achieved by analyzing cores, sediment samples, and wireline logs acquired during IODP Expedition 359, and linking these data to the seismic stratigraphy. The stratigraphic evolution of the Maldives carbonate platform is punctuated by several key intervals which reflect changes in the platform architecture. The different events are (A) the drowning of the Oligocene platform and later development of a restricted environment in the Early Miocene ("Drowning 1), (B) the platform edge reconfiguration from bank margins to platform with hanging shoulders in the Middle Miocene (Hanging shoulders) and (C) the turnover from platform to drift deposition in the Middle Miocene (Drowing 2). The link of these events and global sea level is equivocal and indicates that sea-level fluctuations were not the only drivers of this pattern. Drowning 1 interrupted the Oligocene platform growth, but allowed a later recovery of the platform in a more marginal position during the Miocene. The controlling factor of this drowning episode is yet unclear but may be related to sea-level fluctuations and elevated organic content. Drowning 2 has been related to the occurrence of strong currents due to the onset of the Indian Ocean Monsoon. The demise of large parts of the banks was stepwise and permanent. The other major event, the change from a platform with bank margins to a platform with hanging shoulders in the Middle Miocene is linked to the onset of the Miocene Climate Optimum. A major reconfiguration in the basin occurred coeval to this change in platform edge and slope geometry which is recorded in the sediment with drastic changes in the ichnofabrics and the microfacies. The integrated study of ichnofabrics, microfacies, XRF data, wireline logs and seismic profiles will allow discriminating environmental conditions and relating them to the processes affecting the carbonate platform. Our objective is also to prove that there are different types of drowning affecting carbonate platforms; Some of them interrupt the development of the platform in a reversible way that allow a regeneration of the sedimentary environment, and some of them are completely irreversible and permanently change the sedimentary environment. The working hypothesis is that not only the nutrient input, but also the strength of the currents contribute to these platform reconfigurations. These are results which go far behind the understanding of the regional sedimentology and which have impact for carbonate sedimentological models in general.