Knowledge Resource Center for Ecological Environment in Arid Area
| 罗布泊Ls2孔沉积物近7.1Ma环境磁学研究 | |
| 其他题名 | The environmental magnetism study of 7.1Ma core Ls2 sediment in Lop Nur,Tarim |
| 常秋芳 | |
| 出版年 | 2012 |
| 学位类型 | 硕士 |
| 导师 | 常宏 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 新生代地球上发生了一系列重大地质事件，导致全球气候与环境发生了一系列巨变：全球变冷、北美和亚洲内陆干旱化、亚洲季风形成等。其中，亚洲内陆干旱化是新生代以来地球上相继发生的一系列重大地质事件之一，也是对人类生存环境影响最为深刻和广泛的一个重大科学问题，因此倍受国际社会的关注。揭示亚洲内陆干旱化的起始时间、演化过程和发展规律，探讨其原因，是目前急需解决的问题。前人在该区已从不同方面开展了大量工作，但是由于受到野外工作条件、资料及地球系统各子系统间相互作用机制等的复杂性等客观因素的限制，目前为止，人们对该区的研究仍十分有限，这无疑极大地制约了亚洲内陆干旱化过程的理解。 我国西北地区主要由大型内陆盆地与山脉相间排列组成的盆-山构造，盆地中堆积了巨厚的新生代沉积物，它们详细地记录了我国西北地区干旱化过程，而塔里木盆地就是典型干旱区的代表。它南邻青藏高原，北为天山山脉，自新生代以来一直处于沉积环境之中，对沉积物的系统研究有利于认识青藏高原的隆升过程和亚洲内陆古气候的演化历史。本文研究的罗布泊就是位于塔里木盆地东北部的一个约1050.6m的钻孔岩芯，进而展开对我国内陆干旱化过程及其可能的动力学机制的初步探讨。环境磁学是一门介于地球化学、环境科学和磁学之间的应用岩石磁学和矿物磁学技术去恢复环境过程、重塑环境演化历史的交叉学科。其原理是测量沉积物和岩石等自然物质和人类活动产生的物质在人工磁场中的磁性效应，提取地质-地理环境的信息。 通过对钻孔进行系统的岩石磁学测试，并结合前人已经取得的研究成果，初步探讨了晚新生代罗布泊地区的气候演化特征及其与亚洲内陆干旱化、青藏高原隆升、地中海退却和全球变冷的可能联系，得出以下几点初步结论： 1） 亚铁磁性磁铁矿和反铁磁性赤铁矿是沉积物中的主要的磁性矿物。磁铁矿以PSD和少量的SP 颗粒。 2） S-Ratio值在5.6Ma、3.6Ma和0.74Ma年发生急剧的变化，这一特征指示了同时段的气候变化。 罗布泊气候多磁学参数代用指标的变化，大致可以分为四大阶段： 7.1~5.6Ma期间，为相对湿润与相对干旱气候的交替出现。 5.6~3.6Ma期间，气候干旱化加剧。 3.6~0.74Ma期间，干旱化的趋势有所缓和。 0.74~0Ma干旱化最为剧烈，指示罗布泊地区从湿润到干旱方向演化的趋势。 3） 罗布泊地区早在晚上新世，干旱化步伐开始。磁化率的变化主要受降水强度的控制，磁化率增加反映古降水量增加，反之，则减小。磁化率在5.6~5.1Ma之后下降，说明塔里木盆地晚中新世/上新世分界干旱化趋势开始加重，之后的气候是在干旱环境下的波动。 4) 罗布泊7.1Ma以来的环境演化及其所反映的亚洲内陆干旱化过程与青藏高原的构造隆升过程和北极冰盖的形成、扩张等因素之间存在一定的联系，亚洲内陆干旱化的发展可能受到青藏高原隆升和北极冰盖扩张共同的影响。 |
| 英文摘要 | Since the late Cenozoic, the most important feature of the global environment is the global cooling, the remarkable expanding of arid areas in North America and Asia and the formation of the Asian monsoon et al. Among them, the Asian inland drying is one of the major geological events which has a profound and extensive impact on human survival environment, and has attracted so much international attention. To reveal the start time, evolution process and the law of development of Asian inland drying trendency is an urgent issue need to solve at present. A lot of work in different aspects in this area has carried out by predecessors, but due to objective factors such as working conditions and the limited data, complicated relationship in different spheres of the Earth, and so far, the understanding of the structure is still very limited which undoubtedly greatly restricted the of Asian inland drying processes. Northwest China mainly composed of large inland basins covered by thick Cenozoic sediments which record the drying processes of northwest and ranges which divided these basins. The Tarim basin is a typical representative area. Since Cenozoic it has been in sedimentary environment and deposit huge sediments which record the environmental change process, so it is helpful for understanding the Tibet Plateau uplift process and the evolution of the landlocked Asian paleoclimate history. Lop Nur is in the east of the Tarim Basin, a study on a 1050.6 m-depth core, will reveal some clue on our country inland drying process and its possible dynamics. Environmental magnetism is an edge discipline among geochemistry, environmental science, rock magnetism and mineral magnetism technology, which can be used to reshape the environment evolution history. Its principle is to measure the natural material such as soil, sediment and rock material and human activities in the artificial magnetic field effect to extract environment information of geological and geographical. The results are as follows: 1) Magnetite and hematite make great contribution to the magnetism. Magnetic of PSD was identified as the main magnetic carrier mineral by hysteresis parameters, belong with a small amounts of SP in the lower core. 2) The dramatic transformation of S-Ratio in 5.6Ma、3.6 Ma and 0.74Ma reflects that the climate strengthen the ancient climate magnetic carrier reformation.We infer that the aridity started in 5.6Ma. All magnetic indexes show that the aridification enhanced further in the Tarim Basin during 5.6~3.6Ma. The aridification has been enhanced intensively since 0.74Ma. 3) The drying trend pace had began as early as the late Pliocene . Magnetic in Lop nur susceptibility of the change is mainly controlled by rainfall intensity, magnetic susceptibility increases reflect ancient precipitation increase, on the other hand, is reduced. Magnetic susceptibility in 5.6 ~ 5.1 Ma is down, that reflects the drying trend became serious from late Miocene. 4) The development of the Asian inland aridification may has something with the Tibet Plateau uplift and the expansion of the arctic ice cap. |
| 中文关键词 | 罗布泊 ; 沉积物 ; 晚中新世 ; 岩石磁学 ; 干旱化 |
| 英文关键词 | Lop Nur sediment Late Miocene rock magnetism aridification |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 第四纪地质学 |
| 来源机构 | 中国科学院地球环境研究所 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/287028 |
| 推荐引用方式 GB/T 7714 | 常秋芳. 罗布泊Ls2孔沉积物近7.1Ma环境磁学研究[D]. 中国科学院大学,2012. |
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