The Age Study Of The Xujiayao Site Based On The History Of Regional Volcanic Activity

The origin and evolution of ancient human history has always been one of the important research contents of international ancient anthropology and Quaternary geology.As a typical and representative Quaternary ancient human cultural sites in China,since the ruins of the Xujiayao site.Many archaeologists and geomorphologists have developed a number of dating studies.Because the thickness of the cultural layer of the site is large and the stratigraphic structure is more complicated.the research methods and the means of dating and the judgment of the characteristics of the sampling horizon adopted by different scholars are different.So there are different conclusions of its age from less than twenty thousand years to four or five hundred thousand years.On the basis of combing the predecessors’ research work,this paper finds that the Datong basin,which is located in the ruins of the Xujia kiln,is characterized by frequent volcanic activity under the tectonic movement of the Shan-shan graben.And the Datong volcanic group was composed of 31 volcanic trenches.The same underground magma room provides material sources for volcanic activity.All volcanoes on the surface have some synchronization in eruption time and intensity and comprehensive show the regional volcanic activity of the active and calm period.Volcanic activity in each active period will result in a large amount of volcanic material.And the small particles of volcanic ash have corresponding deposition records in the regional loess-paleosol and lacustrine layers.Chinese Datong volcano activities include Xu Jiayao site.And there must be a sedimentary record corresponding to the regional volcanic active period.The coarse volcanic material can be deposited as a visible volcanic debris layer.In the sedimentary layer of small particles of volcanic ash must be experimental means.In this paper,two complete lacustrine sedimentary facies sections with distance of about1 km were selected in the area of the site.The samples were subjected to the determination of the series parameters,and some samples were subjected to paleomagnetic testing.It was found that the magnetic susceptibility curve of section 1showed four significant positive peaks,corresponding to the Fe and Ti contents in the peak layer of the magnetic susceptibility.the magnetic susceptibility curve of section2 showed only a significant positive peak.The Rb/Sr curve has two opposing valleys at the horizon.The four magnetic susceptibility peaks of section 1 show the fouractive periods of the corresponding volcanic activity in the region.And the peak of the magnetic susceptibility of section 2 corresponds to an active period of the volcanic activity of the region.The numerical relationship between the peak value of the first magnetic susceptibility and the peak value of the profile 2 is similar to the curve,corresponding to the same active period of the volcanic activity of the region.Based on the investigation of the active period of regional volcanic activity,it is found that the Quaternary regional sedimentary records reflect the five active periods of Datong volcanic activity,which are about 0.90 MaB.P(first active period),0.51 MaB.P.(Second active period),0.32 MaB.P.(third active period),0.19 MaB.P.(fourth active period)and 0.09 MaB.P.(fifth active period).Thus,from the perspective of regional volcanic activity stage history,The age scale of the regional volcanic activity was established.The geomagnetism test of the site profile 1 did not exceed0.73 Ma.and the four magnetic susceptibility peaks of section 1 correspond to the last four active periods of the regional volcanic activity.the first magnetic susceptibility peak of section 1 and the peak value of profile 2 magnetic susceptibility peak correspond to the fifth active period of the regional volcanic activity.In addition to recording the volcanic activity of the fifth active period,until the bottom of the section did not find the earlier record of the fourth active period.the cultural age of the site was between the fifth active period to the fourth active period.that is,the cultural age of the site is framed between 0.09 Ma and 0.19 Ma.