科尔沁沙地全新世风沙沉积物的石英单测片蓝光释光测年和风沙活动年代学

SAR dating of quartz and geochronology of Holocene sand dune activities in Horqin sandyfield, China

通过科尔沁沙地内部甘旗卡固定一半固定沙丘地带五个处于不同微地貌的全新世古风沙沉积地层剖面的观测和取样,对25个沙丘砂、古土壤和相关沼泽沉积物样品采用粗颗粒石英单测片蓝光释光测年技术和程序进行沉积年龄测定,并对5个沼泽沉积物和古土壤样品进行有机碳14C年龄测定。在此基础上提出了研究区全新世沙丘活动的年代学框架,即在10-7.5 ka B.P期间沙丘由活动转为固定;约7.5 kaB.P至约(2.0±0.2)ka B.P.期间沙丘广泛发育草原或疏林草原土壤;从约(2.0±0.2)ka B.P以来沙丘又重新进入活动或半活动状态, 并主要取决于人类活动的影响。

After detailed field work on the stabilized and semi-stabilized sand dunes of different micro-geomorphology in Horqin sandyfield, 25 OSL samples and 5 radiocarbon samples are collected for dating to reconstruct the eolian dune activities in the Holocene. Single-Aliquot Regenerative-dose (SAR) protocol was used to determine the equivalent dose (DE) for coarse quartz OSL dating. Based on OSL and 14C dates obtained from five sand dune-soil or swamp sediment profiles, a preliminary geochronology was presented for the sand dune activities in the Holocene. The results show that the sand dune activity was more and more weakly in the early Holocene and stabilized at around 7.5 ka B.P.. The Horqin sandyfield developed its grass soil and corresponding vegetation between 7.5 ka and (2.0±0.2) ka B.P. and the sand dunes were re-active after (2.0±0.2) ka B.P., possibly due to the human activities.