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。要验证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，马尔代夫碳酸盐岩台地将作为海平面和古海洋变化双重控制台地发展的参考案例。这一目标将通过分析岩心、沉积物样本和IODP远征359期间获得的电缆测井数据来实现，并将这些数据与地震地层学联系起来。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层段打断。不同的事件分别是：(A)渐新世台地的淹没和中新世早期有限环境的后期发育（“淹没1”），(B)中新世中台地边缘从岸缘到悬肩的重构（“悬肩”），(C)中新世中台地的翻转到漂移沉积（“淹没2”）。这些事件与全球海平面之间的联系是模棱两可的，这表明海平面波动并不是这种模式的唯一驱动因素。淹没1中断了渐新世台地的生长，但在中新世期间，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。溺死与印度洋季风的爆发导致的强流有关。大部分银行的倒闭是逐步而永久性的。另一个重大事件是中新世中期从一个有河岸边缘的台地到一个有悬肩的台地的变化，这与中新世气候最佳期的开始有关。与此同时，沉积记录了台地边缘和斜坡几何形状的变化，其沉积结构和微相也发生了剧烈变化。对技术结构、微相、XRF数据、电缆测井和地震剖面的综合研究将有助于区分环境条件，并将其与影响碳酸盐岩台地的过程联系起来。我们的目的还在于证明存在不同类型的淹水影响碳酸盐台地；其中一些以可逆的方式中断了台地的发育，使沉积环境得以再生，而另一些则是完全不可逆的，永久地改变了沉积环境。目前的假设是，不仅营养物的输入，电流的强度也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认识，并对一般的碳酸盐沉积学模式产生影响。

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.