内蒙古中部全新统沉积特征与地层划分

Sedimentary characteristics and division of Holocene strata in central Inner Mongolia

文章对内蒙古中部辉腾锡勒湖相沉积剖面及好鲁库风成砂-古土壤剖面全新世地层的沉积特征及^(14)C、OSL测年结果进行了综合论述,根据岩性特征及测年结果确定了全新统的底界。对内蒙古中部全新统沉积序列进行了系统分析,并将其划分为3段:全新统下部(开始于12.5~11.4 ka,结束于8.2~7.0 ka)辉腾锡勒为灰黑色黏土、粉砂质黏土,沉积特征指示由冲积相转变为湖相沉积,湖面开始上升;好鲁库沙丘主要为中粗砂,为风成砂堆积。全新统中部(开始于8.2~7.0 ka,结束于4.5~2.3 ka)辉腾锡勒为灰褐色粉砂质黏土,富含有机质及双壳和螺类化石,为典型湖泊相发育阶段;好鲁库沙丘发育黑色砂质古土壤,气候温暖湿润。全新统上部(开始于4.5~2.3 ka)辉腾锡勒为黏土质粉砂,含植物碎屑,为湖滨相沉积,指示湖泊开始退缩;好鲁库沙丘为灰黄色中粗砂,沙丘重新活化,气候干旱。

The Holocene strata of central Inner Mongolia were investigated using sedimentological features and^(14)C\OSL dating data.The authors present two Holocene profiles that illustrate different sediments from a sand dune in Haoluku, and a lake in Huitengxile.Holocene stratigraphic boundaries are defined by lithological indicators and dating results. The Holocene sequences can be divided into three units. In Huitengxile Lake, the beginning(11.4 ka) of the Holocene was associated with a lake level rise, which led to lithological succession from fluvial clastic sedimentation to lacustrine organic deposition. Sand dune was formed during this period(about 12.5 ka). During the middle Holocene, typical limnological facies(8.2 to 4.5 ka) appeared in Huitengxile Lake, and theclimate turned to be warmer and more humid with the occurrence of thick palaeosoil layers(7.0-2.3 ka) in the dune. Evolution of lacustrine environment followed by nearshore environment was evident from 4.5 ka in late Holocene in Huitengxile Lake, and the period(2.3 ka~) of sand dune reactivation during the drought stage was recorded.