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

该提案的总体目标是解开马尔代夫新近纪古海洋学、海平面和古环境档案。检验的假设是，古海洋变化是碳酸盐岩台地相和地层的主要控制因素。因此，马尔代夫碳酸盐岩台地的开发将成为海平面和古海洋变化对台地开发双重控制的一个参考案例。这一目标将通过分析IODP 359考察期间获得的岩心、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。马尔代夫碳酸盐岩台地的地层演化被几个反映台地结构变化的关键间隔所打断。不同的事件是：（A）渐新世台地的淹没和后来中新世早期局限环境的发展（“淹没1”），（B）中新世中期台地边缘从岸缘到具有悬肩的台地的重新配置（悬肩），以及（C）中新世中期台地到漂流沉积的转换（"淹没2“）。这些事件与全球海平面之间的联系是模糊的，这表明海平面波动不是这种模式的唯一驱动因素。第一次淹没中断了渐新世台地的生长，但在中新世期间允许台地在更边缘的位置恢复。这次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升高有关。溺水2与印度洋季风开始引起的强洋流有关。大部分银行的消亡是逐步和永久的。另一个重大事件，从一个平台与银行边缘的平台与悬肩在中新世中期的变化是与中新世气候最佳的开始。一个主要的重新配置在盆地发生coeval到这个平台的边缘和斜坡的几何形状的变化，这是记录在沉积物中的遗迹组构和微相的急剧变化。通过对遗迹组构、微相、X射线荧光光谱数据、电缆测井和地震剖面的综合研究，可以区分环境条件，并将其与影响碳酸盐岩台地的过程联系起来。我们的目标也是证明有不同类型的溺水影响碳酸盐岩台地;其中一些以可逆的方式中断台地的发展，允许沉积环境的再生，其中一些是完全不可逆的，永久改变沉积环境。工作的假设是，不仅营养输入，而且电流的强度有助于这些平台的重新配置。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.