Refinement of Miocene sea level and monsoon events from the sedimentary archive of the Maldives (Indian Ocean)
Refinement of Miocene sea level and monsoon events from the sedimentary archive of the Maldives (Indian Ocean)
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DOI：
10.1186/s40645-018-0165-x
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发表时间：
2018-01-22
影响因子：
3.9
通讯作者：
Yao, Z.
中科院分区：
文献类型：
--
作者：
Betzler, C.;Eberli, G. P.;Yao, Z.
国际海洋发现方案(IODP)359次探险对印度洋马尔代夫碳酸盐平台的八个钻孔位置的沉积物进行了取芯。考察队着手于揭示新近纪气候变化的时间，特别是南亚季风的演变和海平面的波动。通过测定沉积蚀变的年代来评估这些变化的时间，这些沉积蚀变标志着新近系马尔代夫地台系统的地层学转折点。早、中新世的前四个转折点与海平面变化有关。这些都被可靠地记录在碳酸盐层序的地层学中，其中的层序边界提供了海平面低位的年龄。沉积台地生长阶段给出了早中新世长期海平面高位和早中新世气候最佳时期的准确年龄区间，其年代为17-15.1 Ma。随后的中新世中期降温与南极东部冰盖扩张相一致，导致海平面长期下降，这反映在进积台地的生长上。从沉积到进积的地台结构变化标志着15.1 Ma的这一转折点。在12.9-13 Ma的层序界面上，整个群岛的沉积模式发生了突变。在这一转折点，当季风驱动的环流在印度洋开始时，平台沉积转变为洋流控制模式。整个群岛由季风驱动的环流造成的漂流沉积开始的时间相似，这表明印度洋的季风风突然开始。10个不整合面剖析了漂移序列，证明了洋流强度或方向的变化很可能是过去13 Ma季风强度变化和海平面波动的综合产物。漂移包的一次重大漂移发生在3.8 Ma，与台地阶段性溺水的结束和内海氧最小值带的降低相吻合。马尔代夫地台的地层详细记录了碳酸盐台地生长的外控因素随时间的变化。大洋钻探计划钻探的其他平台已经开发了碳酸盐平台测定新近纪气候和当前变化的潜力。例如，大巴哈马滩、昆士兰高原和马里恩高原上的地台显示出相似的历史，早期(早中新世)由海平面驱动的沉积结构被晚期(中新世晚期)由洋流驱动的溺水或部分溺水所取代。据报道，在这三个地台系统中，洋流对沉积的影响在11-13 Ma之间。
International Ocean Discovery Program (IODP) Expedition 359 cored sediments from eight borehole locations in the carbonate platform of the Maldives in the Indian Ocean. The expedition set out to unravel the timing of Neogene climate changes, in particular the evolution of the South Asian monsoon and fluctuations of the sea level. The timing of these changes are assessed by dating resultant sedimentary alterations that mark stratigraphic turning points in the Neogene Maldives platform system. The first four turning points during the early and middle Miocene are related to sea-level changes. These are reliably recorded in the stratigraphy of the carbonate sequences in which sequence boundaries provide the ages of the sea-level lowstand. Phases of aggradational platform growth give precise age brackets of long-term sea-level high stands during the early Miocene and the early to middle Miocene Climate Optimum that is dated here between 17 to 15.1 Ma. The subsequent middle Miocene cooling coincident with the eastern Antarctic ice sheet expansion resulted in a long-term lowering of sea level that is reflected by a progradational platform growth. The change in platform architecture from aggradation to progradation marks this turning point at 15.1 Ma.& para;& para;An abrupt change in sedimentation pattern is recognized across the entire archipelago at a sequence boundary dated as 12.9-13 Ma. At this turning point, the platform sedimentation switched to a current-controlled mode when the monsoon-wind-driven circulation started in the Indian Ocean. The similar age of the onset of drift deposition from monsoon-wind-driven circulation across the entire archipelago indicates an abrupt onset of monsoon winds in the Indian Ocean. Ten unconformities dissect the drift sequences, attesting changes in current strength or direction that are likely caused by the combined product of changes in the monsoon-wind intensity and sea level fluctuations in the last 13 Ma. A major shift in the drift packages is dated with 3.8 Ma that coincides with the end of stepwise platform drowning and a reduction of the oxygen minimum zone in the Inner Sea.& para;& para;The strata of the Maldives platform provides a detailed record of the extrinsic controlling factors on carbonate platform growth through time. This potential of carbonate platforms for dating the Neogene climate and current changes has been exploited in other platforms drilled by the Ocean Drilling Program. For example, Great Bahama Bank, the Queensland Plateau, and the platforms on the Marion Plateau show similar histories with sediment architectures driven by sea level in their early history (early to middle Miocene) replaced by current-driven drowning or partial drowning during their later history (Late Miocene). In all three platform systems, the influence of currents on sedimentations is reported between 11 and 13 Ma.