基于区域火山活动历史的许家窑遗址年代研究

发布时间：2018-05-19 20:05

本文选题：许家窑遗址 + 火山活动　；参考：《上海师范大学》2017年硕士论文

【摘要】：古人类起源和演化历史一直是国际古人类学和第四纪地质学重要的研究内容之一。作为我国具有典型性和代表性的第四纪古人类文化遗址,许家窑遗址自发现以来,有关遗址文化层即古人类化石所在层位的年代,许多考古学家和地质地貌学家开展了大量的测年研究。由于遗址文化层厚度大、地层结构较复杂,不同学者采用的研究方法、测年手段以及对取样层位的特征判断存在差异,因而关于其年代的结论从不到二万年到四五十万年,分歧很大。本文在梳理前人研究工作的基础上,发现许家窑遗址所处的大同盆地在山陕地堑系构造运动的影响下,火山活动频繁,形成了由31个火山锥组成的大同火山群,为火山活动提供物质来源的为同一个地下岩浆房,地表的所有火山在喷发时间和强度上具有一定的同步性,并综合表现出区域火山活动的活跃期和平静期。每个活跃期内火山活动会带来大量的火山物质,颗粒细小的火山灰物质在区域黄土-古土壤层和湖相层都有相应的沉积记录。许家窑遗址处在我国大同火山活动的影响范围内,必然存在与区域火山活跃期对应的沉积记录,颗粒较粗的火山物质可沉积形成为肉眼可见的火山碎屑层,而夹杂在沉积层中颗粒细小的火山灰物质须通过实验手段来显示。本文在遗址范围内选取了两个相距1km左右的完整湖相沉积层剖面进行采样,并对样品进行了沉积系列参数的测定和部分样品的古地磁测试。结果发现剖面1的磁化率曲线呈现四个显著正异常的峰值,对应于磁化率峰值层位处Fe、Ti含量也很高,剖面2的磁化率曲线仅呈现一个显著正异常的峰值,在该层位处Rb/Sr曲线存在两个相对的低谷。显示剖面1的四个磁化率峰值对应区域火山活动的四个活跃期,剖面2的磁化率峰值对应区域火山活动的一个活跃期。剖面1第一个磁化率峰值和剖面2磁化率峰值的数值关系和曲线形状相似,对应区域火山活动的同一个活跃期。基于区域火山活动活跃期年代的调查研究,发现第四纪区域沉积记录反映大同火山活动有五个活跃期,其形成年代大约分别为早于0.90MaB.P.(第一活跃期)、0.51MaB.P.(第二活跃期)、0.32MaB.P.(第三活跃期)、0.19MaB.P.(第四活跃期)和0.09MaB.P.(第五活跃期)。由此,从区域火山活动阶段性历史的角度,建立了区域火山活动的年代标尺。遗址剖面1的古地磁测试其年代未超过0.73Ma,因而剖面1四个磁化率峰值对应了区域火山活动的后四个活跃期,剖面1第一个磁化率峰值和剖面2磁化率峰值均对应区域火山活动的第五活跃期。遗址剖面2除了记录火山活动的第五活跃期外,直至剖面底部未发现更早的第四活跃期沉积记录,遗址文化层年代在第五活跃期至第四活跃期之间,即遗址文化层年代被框定在距今0.09Ma至0.19Ma之间。
[Abstract]:The origin and evolution history of paleoanthropology has been one of the important contents of international paleoanthropology and Quaternary geology. As a typical and representative Quaternary ancient human cultural site, Xujiayao site has been discovered since its discovery. Many archaeologists and geomorphologists have carried out a lot of dating studies. Due to the large thickness of the cultural layer and the complicated stratigraphic structure of the site, there are differences in the research methods, dating methods and the characteristics of the sampling horizon adopted by different scholars. Therefore, the conclusion on the age of the site ranges from less than 20,000 years to 4.5 million years. The difference is wide. On the basis of previous research work, this paper finds that the Datong basin, which is located at Xujiayao site, is under the influence of the tectonic movement of the Shanshan graben system, and the volcanic activity is frequent, forming the Datong volcanic group, which is composed of 31 volcanic cones. The same underground magma chamber is the source of material for volcanic activity. All the volcanoes on the surface have a certain synchronism in eruption time and intensity, and show the active period and quiet period of regional volcanic activity synthetically. During each active period volcanic activity brings a great deal of volcanic material and the fine particles of volcanic ash are recorded in the regional loess paleosol layer and lacustrine facies. Xujiayao site is located within the influence of Datong volcanic activity in China, and there must be sedimentary records corresponding to the regional volcanic active period. The coarse volcanic material can be deposited into a visible volcanic clastic layer. The pozzolanic material mixed with fine particles in the sediment must be shown experimentally. In this paper, two intact lacustrine sedimentary sections about 1km are selected for sampling, and the parameters of sedimentary series and paleomagnetic test of some samples are measured. The results show that the magnetic susceptibility curve of section 1 shows four peaks of significant positive anomalies, corresponding to the high content of Feti at the peak layer of magnetic susceptibility, and the susceptibility curve of section 2 shows only one peak value of significant positive anomalies. There are two relative lows in the Rb/Sr curve at this layer. It is shown that the four peaks of magnetic susceptibility of section 1 correspond to four active periods of regional volcanic activity, and the peak of magnetic susceptibility of section 2 corresponds to an active period of regional volcanic activity. The numerical relationship between the first susceptibility peak of section 1 and the peak value of magnetic susceptibility in section 2 is similar to the shape of the curve, which corresponds to the same active period of regional volcanic activity. Based on the investigation and study of the active periods of regional volcanic activity, it is found that the Quaternary regional sedimentary records show that there are five active periods in Datong volcanic activity, which are formed earlier than 0.90 MaB.Prespectively. (the first active period: 0.51MaB.P. (the second active period is 0.32 MaB.P. (the third active period is 0.19 MaB.P. (fourth active period) and 0.09 MaB.P. The fifth active period. Therefore, the chronological scale of regional volcanic activity is established from the point of view of regional volcanic activity stage history. The paleomagnetism of site section 1 is less than 0.73 Ma, so the 14 peaks of magnetic susceptibility of section 1 correspond to the last four active periods of regional volcanic activity. The first susceptibility peak in section 1 and the magnetic susceptibility peak in section 2 correspond to the fifth active period of regional volcanic activity. Site section 2 except for the fifth active period of volcanic activity, until no earlier sedimentary records of the fourth active period were found at the bottom of the section, the age of the site cultural layer was between the fifth active period and the fourth active period. In other words, the time of the cultural layer of the site was framed between 0.09Ma and 0.19Ma.
【学位授予单位】：上海师范大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：K878;P317

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