摘要
利用光释光测年技术,获得了覆盖科尔沁沙地内部及外围的20个风成沙-砂质古土壤沉积序列的年代。在分析前人研究的基础上,结合地层和气候代用指标重建了末次盛冰期以来科尔沁沙地的演化过程。结果表明:科尔沁沙地的气候变化和沙丘的固定与活化主要经历了4个阶段,即:26~12ka,气候极端干冷,沙地大面积活化;12.0~9.5ka,气候趋于暖湿,但仍比较干冷,沙地由大规模沙化向固定成壤过渡;9.5~2.5ka,气候暖湿,沙地基本固定;2.5ka以来,气候呈干冷与暖湿交替状态,沙地亦存在多次固定与活化,其中,从1.5ka开始,沙丘活化明显。基于风沙沉积序列的空间分布和光释光测年结果,末次盛冰期科尔沁沙地同时向南和北扩展:南至翁牛特-库伦旗一线,至少扩张了26km;北至霍林河一带,至少扩张了30km;东界受东辽河限制,与现代边界几乎一致。沙地面积较现代扩张了至少2.05×10~4km^2,扩大了37.7%。全新世大暖期,沙丘大面积固定。研究表明,科尔沁沙地气候与环境演变受东亚季风影响,也是全球气候变化的区域响应。
The Horqin dunefield, which is located in margin of the region dominated by East Asian monsoon circulation,is sensitive to climatic changes. However, paleoclimatic and the border changes of Horqin dunefield during Late Quaternary remain poorly understood, partly due to lacking high quality age controls. In this study, optical stimulated luminescence （OSL）technique and multi-proxy analysis of the sediment sequence from Horqin dunefield,including sedimentary facies, magnetic susceptibility and grain size distribution, was used to document the changes of paleoclimate and the borders of the dunefield since Last Glacial Maximum （LGM）. 20 typical dune sand sections were dated by OSL technique and 85 luminescence ages at the LGM have been obtained. It suggests that the dunes were mobilized with cold and dry climate during 26 ~ 12ka. Subsequently, the dunes changed from large-scale active to local stabilized with relatively warm and wet climate during 12.0 - 9.5ka. After that,the dunes were completely stabilized during 9.5 - 2.5ka with the climate was the warmest and most humid. After that, several mobilization/stabilization cycles of the dunes which were associated with dry-cold/ wet-warm variations occurred since 2.5ka, the dunes have been activated within the entire region after 1.5ka. On the basis of these dating results and the spatial- and temporal- distribution of the sand deposit, we conclude that the Horqin dunefield expanded at least 26km to south and 30km to north during the Last Glacial Maximum, at the same time,the eastern border was limited by the East Liao River as that of the present. The Horqin dunefield expanded around 2.05× 104km2 in the Last Glacial Maximum, 37.7% larger than that of the present area. During the Holocene climatic Optimum, the mobile dunes were fully stabilized in the Horqin dunefield. These climate and environment changes in Horqin dunefield can be regarded as a regional response to the global climate changes.
出处
《第四纪研究》
CAS
CSCD
北大核心
2013年第2期206-217,共12页
Quaternary Sciences
基金
国家自然科学基金项目(批准号:40930103
40902045和41021002)
全球变化研究国家重大科学研究计划项目(批准号:2010CB950203)共同资助
关键词
末次盛冰期
全新世大暖期
科尔沁沙地
气候变化
沙地边界重建
Last Glacial Maximum, Holocene Optimum, Horqin dunefield, climate change, reconstructionof the dunefield border
