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上新世以来东阿拉伯海沉积物碎屑态来源及其对南亚季风的响应
蔡明江
学位类型硕士
导师于心科
2017-05-12
学位授予单位中国科学院大学
学位授予地点北京
学位专业海洋地质
关键词阿拉伯海 粘土矿物 印度河 德干高原 南亚季风
摘要为研究东阿拉伯海地区上新世以来岩芯沉积物碎屑态的来源及其古环境指示意义,本文对阿拉伯海东部IODP U1456站上新世以来陆源碎屑沉积物进行了粒度、粘土矿物各组分含量相对变化分析工作,查明了阿拉伯海东部地区陆源碎屑沉积物的来源。确定物源后与U1456站沉积物MS、NGR、TC、TN、TOC、TIC、TOC/TN、Bsi等指标进行了对比,获得了5.3 Ma以来U1456站粘土矿物指标与上述指标之间良好的对应关系,最后探讨了研究区碎屑物质来源变化的控制因素。结果显示:
U1456站岩芯陆源碎屑沉积物中粘土矿物主要包括为伊利石、蒙脱石、绿泥石、高岭石。主要组分为蒙脱石和伊利石(二者平均含量之和>80%),次要组分为绿泥石和高岭石(二者平均含量之和<20%)。
各阶段粘土矿物各组分相对含量的增多与减少呈现出明显的阶段性。依据粘土矿物中蒙脱石、伊利石、高岭石、绿泥石四种组分的相对含量及变化趋势,可以将上新世以来U1456站粘土矿物变化分为四个阶段:阶段1(早上新世至中上新世;5.3-3.2 Ma),阶段2(中上新世至早更新世;3.2-1.7 Ma)阶段3(早更新世;1.7-1.2 Ma),阶段4(早更新世至今;1.2-0 Ma)。
粘土矿物各组分相对含量变化显示, IODP U1456站陆源碎屑沉积物在5.3-3.2 Ma和1.7-1.2 Ma主要来源于印度河;在 3.2-1.7 Ma和1.2-0 Ma,则主要来自于印度河与德干高原。
上新世以来,陆源碎屑沉积物向阿拉伯海东部的输入在构造尺度上受南亚季风强度控制。南亚季风强度变化是触发IODP U1456站陆源碎屑沉积物在3.2 Ma、1.7 Ma、1.2 Ma发生转变的关键因素。在东阿拉伯海,由于德干高原对南亚季风强度的反应更加敏感,当南亚季风强度弱时,陆源碎屑沉积物主要来源于印度河;南亚季风强度强时,德干高原输入的陆源碎屑沉积物明显增多。
1.7-1.2 Ma,IODP U1456站陆源碎屑物质沉积速率明显增大可能是一个地区和全球性的叠加事件。部分原因是恒河在喜马拉雅山脉西部的一条支流改道成为印度河的支流;部分原因是由于气候偏移,从相对稳定的气候转为急剧波动的气候所引起的全球性事件。最终导致全球陆表风化剥蚀速率迅速增加两者共同导致更多的来自喜马拉雅地区的碎屑沉积物由印度河输入阿拉伯海。
在构造时间尺度上,上新世以来东阿拉伯海地区蒙脱石/(伊利石+绿泥石)表征的德干高原相对于印度河输入量的变化与南亚季风变化之间存在很好的耦合关系。蒙脱石/(伊利石+绿泥石)比值增大,南亚季风强度增强;蒙脱石/(伊利石+绿泥石)比值减小,南亚季风强度减弱。因此在构造时间尺度上,上新世以来东阿拉伯海地区陆源碎屑沉积物中的蒙脱石/(伊利石+绿泥石)可以做为南亚季风强度强弱变化的指标。
其他摘要Clay mineral and grain sizes of detrital sediments fraction samples for site U1456 based on the samples acquired during the International Ocean Discovery Program (IODP) Expedition 355 from the east Arabian sea were studied for reconstruction of sediments provenance and paleoenvironment since the Pliocene. There is a good correspondence between the clay mineral and MS, NGR, TC, TN, TOC, TIC, TOC / TN of site U1456 during the 5.3 Ma. Finally, the controlling factors of the source of detrital sediments in the the east Arabian sea were discussed. The results are as follows:
The results show that the main components of clay minerals in the terrigenous sediments of U1456 are composed of illite, montmorillonite, chlorite and kaolinite. The main components are montmorillonite and illite (the average content of montmorillonite and illite> 80%), the secondary components are chlorite and kaolinite (the average content of the chlorite and kaolinite <20%).
The variety of the clay minerals show obvious phase since the Pliocene in site U1456. Based on the variations of the montmorillonite, illite, kaolinite and chlorite in clay minerals compositions since the Pliocene, the site U1456 could be divided into five distinct depositional units. Zone 1(early to middle Pliocene; 5.3-3.2 Ma), Zone 2( middle Pliocene to early Pleistocene; 3.2-1.7 Ma), Zone 3 (middle Pleistocene; 1.7-1.2 Ma), Zone 4 (middle Pleistocene to Holocene; 1.2-0 Ma).
Clay mineral distribution show that the sediment in IODP Site U1456 are mainly from the Indus River during 5.3-3.2、1.7-1.2 Ma and a significant increasing of supply of Deccan Trap sediment have been observed during 3.2-2.39、1.2-0 Ma.
On tectonic scale, the input of terrigenous detrital sediments to the east Arabian Sea was dominated by the South Asian monsoon intensity since the Pliocene. The shift of the IODP U1456 station sediment sources around 3.2 Ma, 1.7 Ma, 1.2 Ma could be interpreted as the change of the South Asian monsoon intensity. The response of the South Asian monsoon intensity in Deccan Traps is more sensitive. The terrigenous detrital sediments in the east Arabian Sea were mainly derived from the Indus River when the South Asian monsoon was persistently weaker; however, the terrigenous detrital Sediment increased significantly when the South Asian monsoon was persistently stronger.
We propose that the change of mass accumulation rate in site U1456 was partly caused by a regional and global superposition event. And a large rivers in Punjap flowed into the Indus,which flowed into the Gunges river before that time is another reason. Part of the reason was due to climate shift caused by global events, which was from a relatively stable climate to a rapidly fluctuating climate. The two factors led to more detrital sediments from the Himalayan region into the Arabian Sea by the Indus.
On the tectonic time scale, there is a good coupling between the changes in the sediments input of the Indus and the South Asian monsoon in the Deccan Traps, characterized by montmorillonite/(illite/chlorite) in the Eastern Arabian Sea since the Pliocene. The ratio of montmorillonite/(illite/chlorite) decreases with the increase of South Asian monsoon intensity, and the decrease of South Asian monsoon intensity occurs simultaneously. Therefore, montmorillonite/(illite/chlorite) in the detrital sediments of the East Arabian Sea region can be used as an indicator of the intensity of the South Asian monsoon intensity on the tectonic time scale since the Pliocene.
学科领域海洋地质学
语种中文
文献类型学位论文
条目标识符http://ir.qdio.ac.cn/handle/337002/136646
专题海洋地质与环境重点实验室
作者单位中国科学院海洋研究所
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蔡明江. 上新世以来东阿拉伯海沉积物碎屑态来源及其对南亚季风的响应[D]. 北京. 中国科学院大学,2017.
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