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| 黄河中游沙丘活化和古水文事件的光释光测年研究 | |
| 其他题名 | Optically Stimulated Luminescence dating of dune activation and the hydrological events in the middle reaches of the Yellow River |
| 杜金花 | |
| 出版年 | 2014 |
| 学位类型 | 博士 |
| 导师 | 孙有斌 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 黄河为我国的第二大河流，流经我国的西北干旱区，因此黄河中游地区研究我国干旱半干旱区气候事件（如沙地活化事件或古水文事件）理想区域。准确的测定年轻（小于1000年）的风成沙丘砂年龄一直困扰着实际测年方法本身及其该时段的气候变化研究。本文选取黄河中游大荔沙苑（下洼地剖面）的粗颗粒石英样品为研究对象，针对年轻沙丘沉积物中石英光释光信号量普遍不足的问题开展了年轻沉积物光释光测年方法学研究，并且将其应用到黄河中游的毛乌素和大荔沙苑沙地沙丘砂定年。同时，对沙苑所在的渭河流域的王店剖面和湘桥剖面的开展了光释光年代学及其多种环境代用指标的研究，获得的主要结论和认识如下： 1、针对国际通用的单片再生法较难测定年轻沉积物中暗石英光释光年龄的问题，即低的光释光信号量，导致低的信号噪音比，无法可靠地建立单片的生长曲线，提出加热型单片再生法。利用大荔沙苑沙丘的下洼地剖面沙丘砂石英样品进行了通用型和加热型单片再生法研究结果表明，对于下洼地剖面较老样品IEE3565，加热至500度可提高光释光信号量一个数量级，但通用型和加热型单片再生法的年龄测定结果在误差范围内是一致的。对于年轻的样品IEE3534而言，国际通用的单片再生法很难在单一测片上建立可靠的生长曲线，进而难以进行单片再生法测年。加热型单片再生法通过加热提高光释光信号量后可以建立可靠的生长曲线，其剂量恢复实验的结果也表明能够进行年轻石英样品光释光测年。 2、将加热型单片再生法运用于黄河中游毛乌素和大荔沙苑沙地沙丘风成砂光释光定年，结果表明毛乌素沙地记录了LGM、YD和LIA时期的3次沙丘活化事件；大荔沙苑记录了LGM和LIA时期2次沙丘活化事件；进一步分析结果表明不仅毛乌素和大荔沙苑沙地最近的流动沙丘形成年龄为小冰期，整个北方沙漠最近一次的沙丘也是发育于小冰期，且与历史文献记载的断代年龄相符合，证明了加热型单片再生法可测定小于1000年的年轻石英颗粒的光释光年龄，从而为我国北方干旱半干旱区域年轻的碎屑沉积物测年提供了新的技术。 3、对黄河中游沙苑沙地的王店剖面（WD）和湘桥剖面（XQ）的粒度、磁化率、TOC和色度环境代用指标结合光释光年龄分析的结果表明，末次冰期以来研究区域内记录了38-45kaBP、LGM及其14.2-15.5 kaBP时期三次重要的古水文事件。全新世以来记载了3次重要的古水文事件事件，分别发生于9.47±0.17 kaBP，7.43±0.19 kaBP和4.54±0.11 kaBP。 4、探讨黄河中游区域气候对全球气候事件的响应。毛乌素和大荔沙苑沙地明确地记录了末次冰盛期、末次冰期向全新世过渡期间的Younger Dryas 事件以及小冰期事件。王店剖面和湘桥剖面光释光测年结果显示末次冰期的古水文事件发育时期对应太阳辐射的低值，而全新世古洪水事件发生时期对应其黑子活动的低值。这一结果揭示黄河中游干旱半干旱区域气候变化对其全球气候变化产生灵敏的响应，但是对其驱动过程仍然不清楚。 |
| 英文摘要 | It is an ideal region to investigate the characteristics of sand dunes activities and hydrological events in the middle reach of the Yellow River, the second longest river. There is no reliable dating method for young sand dune (e.g. <1000 years), which limited the understanding the sand dune acitivity. Optically stimulated Luminescence dating is one of the promising ways to solve this problem. In this study, we selected coarse quartz grains extracted from the Xiawadi section in the Dali dune field as the research object. It was found that the quartz OSL signal is dim. Here we report some attempts to overcome the problems that result from the low signal/noise ratio when using the OSL dating. We will apply a modification OSL dating method to young sand dunes Mu us and Shayuan sandy lands in central China. Meanwhile, the OSL dating and various environment indexes were carried out at the Wangdian and Xiangqiao sections where were lie in the region between the Luo River and the Wei River, first-order tributaries of the Yellow River. The primary conclusions are drawn as follows: 1. Quartz with low OSL sensitivity has limited the OSL dating of late Holocene sediments, especially with ages of less than 1,000 years, when the classic SAR protocol was applied, because low OSL sensitivity leads to a low signal/noise ratio, failure to construct a dose response curve. Here we come up with a modified SAR protocol in which annealing to 500 oC is used to increase the OSL sensitivity prior to construction of the dose response curve. Two samples (IEE3534 and IEE3565, with depths of 0.5 and 11 m, respectively) from Dali sand dunes, central China, were used for experiments to investigate the effect of annealing. The SAR protocol was used to determine De values without and with annealing at 500 oC of sample IEE3565, the result show that such annealing seems to have little influence on the OSL dating results for the older sample. For the younger sample, it is difficult to construct a sufficiently precise dose response curve for De determination on a single aliquot, thus it is concluded that additional annealing in the SAR protocol is helpful for constructing a reliable dose response curve, even when using only a single aliquot. 2. The SAR protocol with annealing was applied quartz-grain from the Mu Us and Shayuan sandy lands. The OSL results show that three periods of sand dunes activities occurred in Mu Us sand field, they are the Last Glaciation Maximum (LGM), the Younger Drays and the Little Ice Age. In Shayuan, sand dune developed during the LGM and LIA periods. It is found that the last sand dune activities happened during the LIA periods, not only in Mu Us and Dali sand fields, but also in other deserts in North China. This fact is also confirmed by the historical documents. 3. The hydrological events were recovered from Weihe basin (Wangdian and Xiangqiao sections). The OSL dating results, combined with climate proxies (e.g. grain size, magnetic susceptibility, TOC and color) proved that there have three paleo-hydrological events, developing in the 38-45 kaBP、LGM and 14.2-15.5 kaBP during the past 50kaBP. In the Holocene three flood events occurred in the period of 9.47±0.17 kaBP，7.43±0.19 kaBP and 4.54±0.11 kaBP. 4. Both sand dune acitities and hydrological events were used to interprate the regional climate response to the global changes. It is confirmed that sand dune activation happens at cold and dry climate condition, which are the LGM, YD and LIA in the middle reach of the Yellow River. The glacial hydrological events happen at the low values of solar radiation, and the Holocene hydrological events may be linked to the Sunspot Activity. These results imply that the climate change of the study area was more responsive to the global climate events, but it remains unclear whether driving mechanism was same. |
| 中文关键词 | 黄河中游 ; 光释光测年 ; 沙丘活化 ; 古水文 |
| 英文关键词 | Middle reaches of the Yellow River OSL dating Dune activation Hydrological events |
| 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/2XILL650/287365 |
| 推荐引用方式 GB/T 7714 | 杜金花. 黄河中游沙丘活化和古水文事件的光释光测年研究[D]. 中国科学院大学,2014. |
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