The Middle to Late Miocene “Carbonate Crash” in the Equatorial Indian Ocean
The Middle to Late Miocene “Carbonate Crash” in the Equatorial Indian Ocean
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DOI：
10.1029/2018pa003482
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发表时间：
2019-05
影响因子：
3.5
通讯作者：
J. Lübbers;W. Kuhnt;A. Holbourn;C. Bolton;E. Gray;Y. Usui;K. Kochhann;S. Beil;N. Andersen
中科院分区：
文献类型：
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作者：
J. Lübbers;W. Kuhnt;A. Holbourn;C. Bolton;E. Gray;Y. Usui;K. Kochhann;S. Beil;N. Andersen
我们将底栖有孔虫稳定同位素，X射线荧光元素比率和碳酸盐累积估计值整合在国际海洋发现计划站点U1443（印度洋Ninetyeast Ridge）恢复的连续沉积档案中，以重建1350万至820万年前碳酸盐沉积和气候演变的变化。在~13.2 Ma之后，碳酸盐百分比的下降以及碳酸盐累积速率的显著降低标志着碳酸盐沉积减少的长期事件的开始。这一扩展阶段持续到~8.7 Ma，与中新世中晚期碳酸盐崩溃相吻合，最初在赤道东太平洋和加勒比海发现。跨洋比较表明，在站点U1443（~11.5 ~~10 Ma）的强烈碳酸盐剥蚀与所有主要热带海洋盆地的碳酸盐沉积减少的长期事件相吻合。这意味着全球化学风化强度的变化以及河流向海洋水库中输入的钙和碳酸盐离子有助于推动碳酸盐崩溃。U1443 Log（Ba/Ti）的增加以及沉积物颜色从红色到绿色的变化表明，在~11.2 Ma之后，有机输出通量增加到海底，这早于全球生物水华的发生。生物生产的输出通量的这种早期上升可能与营养物质平流的增加和上层海洋混合的加剧有关，这与印度季风的季节性和强度的变化有关。
We integrate benthic foraminiferal stable isotopes, X‐ray fluorescence elemental ratios, and carbonate accumulation estimates in a continuous sedimentary archive recovered at International Ocean Discovery Program Site U1443 (Ninetyeast Ridge, Indian Ocean) to reconstruct changes in carbonate deposition and climate evolution over the interval 13.5 to 8.2 million years ago. Declining carbonate percentages together with a marked decrease in carbonate accumulation rates after ~13.2 Ma signal the onset of a prolonged episode of reduced carbonate deposition. This extended phase, which lasted until ~8.7 Ma, coincides with the middle to late Miocene carbonate crash, originally identified in the eastern equatorial Pacific Ocean and the Caribbean Sea. Interocean comparison reveals that intense carbonate impoverishment at Site U1443 (~11.5 to ~10 Ma) coincides with prolonged episodes of reduced carbonate deposition in all major tropical ocean basins. This implies that global changes in the intensity of chemical weathering and riverine input of calcium and carbonate ions into the ocean reservoir were instrumental in driving the carbonate crash. An increase in U1443 Log (Ba/Ti) together with a change in sediment color from red to green indicate a rise in organic export flux to the sea floor after ~11.2 Ma, which predates the global onset of the biogenic bloom. This early rise in export flux from biological production may have been linked to increased advection of nutrients and intensification of upper ocean mixing, associated with changes in the seasonality and intensity of the Indian Monsoon.