The Relationship between Environmental Changesand Human Activities Duringthe Medieval Warm Periodandthe Little Ice Agein Otindag Sandlandby Osl Dating
详细信息
- 责任者：Zhang Xiaoyan(College of Tourism and Environment ; Shaanxi Normal University ; Xi’ an 710062) ; Zhou Yali
- 刊名：Quaternary Sciences
- 出版年：2012
- 卷期：32(3)
- 页码：p.535-546
- issnNo：ISSN1001-7410
- isbnNo：CN11-2708/P
摘要
Otindag sandland is located in the middle of Inner Mongolia Plateau(112°22’~117°57’N,41°56’~44°24’E),with its present environment is arid to semiarid.The climate is mainly controlled by the East Asian monsoon atmospheric circulation in this region.The earth surface processes,such as dune systems,are sensitive to both climatic changes and human impacts.In order to better understand the interaction of these factors in Otindag sandland during the Medieval Warm Period and the Little Ice Age, optically stimulated luminescence dating(OSL)has been used to obtain ages of five typical dune sediment sequences,which are LQD(42.26°N,116.13°E),S308-132km(42.39°N,115.39°E),HSZN(42.08°N,116.44°E),DLGES(43.56°N,115.68°E) and JPW-A(43.24°N,117.45°E),with the thickness as 2.0m,1.4m,3.0m,2.2m and 0.8m,respectively.OSL dating on quartz grains at the size of 90~150μm were carried out by using the single aliquot regenerative-dose(SAR)protocol.
Combined with the characteristics of grain-size distribution, magnetic susceptibility,ignition loss from the sediment and the pottery sherds which were found in LQD and JPW-A sediment sequences,paleoenvironmental changes were reconstructed since 2ka in Otindag sandland.Sandy soil with greater value of silt and clay content,magnetic susceptibility,and loss on ignition were developed in the episode of 1.45~1.10ka and 0.83~0.58ka,while yellow sand layer with more coarse grain,less silt and clay and magnetic susceptibility as well as loss on ignition were developed at 1.10~0.83ka and 0.58~0.20ka.The development of sandy soil represents wetter and warmer conditions,leading to the increase of vegetation coverage and much less aeolian activity.These phases were the warming periods of Tang Dynasty and the Yuan Dynasty in Chinese history correlating with the Medieval Warming Period in Europe.In that time,the ideal natural environment helped the great development of the culture of dry fanning agriculture.The activation of dunes with sand deposit indicates colder and drier climate,resulting in the lower vegetation coverage and the desertification.These periods are consistent with Song Dynasty and Qing Dynasty,respectively,in China history.Especially,the range of 0.58~0.20ka is corresponding to the Little Ice Age when nomadic culture was developed in this region.Since 2ka,human activity such as living and cultivation depended greatly on natural environmental changes.During warming periods,dry farming culture was developed with flourishing civilization.In cold and dry periods,nomadic culture was dominant and the lack of production could trigger off famine and drought,as well as the war between northern and southern flocks,leading to social upset.
Combined with the characteristics of grain-size distribution, magnetic susceptibility,ignition loss from the sediment and the pottery sherds which were found in LQD and JPW-A sediment sequences,paleoenvironmental changes were reconstructed since 2ka in Otindag sandland.Sandy soil with greater value of silt and clay content,magnetic susceptibility,and loss on ignition were developed in the episode of 1.45~1.10ka and 0.83~0.58ka,while yellow sand layer with more coarse grain,less silt and clay and magnetic susceptibility as well as loss on ignition were developed at 1.10~0.83ka and 0.58~0.20ka.The development of sandy soil represents wetter and warmer conditions,leading to the increase of vegetation coverage and much less aeolian activity.These phases were the warming periods of Tang Dynasty and the Yuan Dynasty in Chinese history correlating with the Medieval Warming Period in Europe.In that time,the ideal natural environment helped the great development of the culture of dry fanning agriculture.The activation of dunes with sand deposit indicates colder and drier climate,resulting in the lower vegetation coverage and the desertification.These periods are consistent with Song Dynasty and Qing Dynasty,respectively,in China history.Especially,the range of 0.58~0.20ka is corresponding to the Little Ice Age when nomadic culture was developed in this region.Since 2ka,human activity such as living and cultivation depended greatly on natural environmental changes.During warming periods,dry farming culture was developed with flourishing civilization.In cold and dry periods,nomadic culture was dominant and the lack of production could trigger off famine and drought,as well as the war between northern and southern flocks,leading to social upset.