楚纯洁^1,2,,
赵景波^2,,,
周金风³
1. 平顶山学院资源与环境科学学院, 河南 平顶山 467000
2. 陕西师范大学旅游与环境学院, 陕西 西安 710119
3. 平顶山学院化学与环境工程学院, 河南 平顶山 467000

基金项目: 国家自然科学基金国际合作项目（批准号：41210002）、河南省高校青年骨干教师资助计划项目（批准号：2014GGJS-141）平顶山学院高层次人才资助项目（批准号：2016GR06）共同资助


详细信息

作者简介: 楚纯洁, 男, 40岁, 副教授, 自然地理、生态环境演变研究, E-mail:zzfccj@163.com

通讯作者: 赵景波, E-mail:zhaojb@snnu.edu.cn

中图分类号: P534.63;P941.73;P597⁺.3

收稿日期:2017-05-09
修回日期:2017-12-06
刊出日期:2018-05-30

Sedimentary characteristics and stratigraphic division of the loess-paleosol section in Wushen County, the central Mu Us dune field in North China

Chu Chunjie^1,2,,
Zhao Jingbo^2,,,
Zhou Jinfeng³
1. College of Resources and Environmental Science, Pingdingshan University, Pingdingshan 467000, Henan
2. College of Tourism and Environment, Shaanxi Normal University, Xi'an 710119, Shaanxi
3. College of Chemistry and Environmental Engineering, Pingdingshan University, Pingdingshan 467000, Henan


More Information

Corresponding author: Zhao Jingbo,E-mail:zhaojb@snnu.edu.cn

MSC: P534.63;P941.73;P597⁺.3

--> Received Date: 09 May 2017
Revised Date: 06 December 2017
Publish Date: 30 May 2018


摘要
摘要:毛乌素沙地保存着晚第四纪以来的多种沉积序列，记录了过去数十万年以来的古气候变化信息。文章通过地层对比与OSL测年相结合，建立了毛乌素沙地中部乌审旗地区发育厚11.6 m的MLL黄土剖面245 ka B.P.以来的年代框架，并对地层划分、沉积特征及其古环境指示意义进行了分析。结果表明：MLL地层剖面是与黄土高原地区相似但又具有特殊性的黄土-古土壤序列，同时也明显不同于沙漠-黄土过渡带常见的古风成砂-古土壤序列。该剖面出露了L₃以上连续稳定的黄土-古土壤沉积层以及地表风沙层FS。L₁的上下砂黄土层之间夹有一个弱发育古土壤层，S₁和S₂分别具有两个古土壤复合层，紧接S₁、S_2a、S_2b及L_1b底部发育有连续稳定的钙结核淀积层。地表风沙层下部有薄层弱发育砂质土层，未见明显的全新世中期古土壤（S₀）发育。L₁、S₁与S₂具有与典型黄土相似的一般特征，可作为MLL剖面地层划分以及年龄控制的标志层。MLL剖面黄土层和古土壤层中的砂质成分含量均较高，>63 μm砂粒含量分别达到了57.11%和44.77%，但在全剖面未见埋藏古风成砂层存在。MLL剖面CaCO₃含量的旋回变化与黄土高原地区一致，黄土层CaCO₃含量显著高于古土壤层，发育较好的S_1b、S_2b中CaCO₃含量分别只有0.13%、1.31%。MLL剖面不同层次之间的磁化率对比不明显，黄土磁化率值与古土壤相差极小。245 ka B.P.以来强劲的冬季风作用和风尘堆积，使毛乌素沙地中部一直处于鄂尔多斯高原"风沙高原"的控制之下，即使在暖湿气候条件下的间冰期，粘化层风化淋滤作用也相对较弱。
关键词: 毛乌素沙地/
黄土-古土壤/
沉积特征/
地层划分/
古环境

Abstract:The Mu Us dune field accumulated a sedimentary sequence since the Late Quaternary, and recorded paleoclimate change information over the past hundreds of thousands of years. Through a field investigation of the Mu Us dune field from November, 2013 to July, 2014, the author found a continuous and complete sedimentary loess-paleosol sequence section(MLL section) with high-resolution stratigraphy and intact preservation in a sand-covered loess region of the central Mu Us dune field. The section is located in a loess ridge, about 15.8 km from southeastern Wushen County, at 38°28'21″N and 108°45'55″E, and with an average thickness of 12 m, but the thickness of the section studied in this paper is 11.6 m. Based on OSL dating and the age comparisons of standard loess strata in the Loess Plateau, the chronological framework of the MLL section was established as 245 ka B.P., and the stratigraphic divisions, sedimentary characteristics, and paleoenvironmental significance were analyzed. The results of this analysis show that the MLL section is a loess-paleosol sequence which is substantially similar to the Loess Plateau. At the same time, the MLL section is significantly different from the eolian sand-paleosol sequences often found in desert-loess transitional zones. The section is an outcrop of stable loess paleosol deposits above L₃ and the surface aeolian sand layer FS. L₁ has three sub-layers in which a weakly developed paleosol layer is situated between the upper L_1a and lower L_1c loess layer. S₁ and S₂ paleosols contain two composite layers. In addition, clear calcium illuvial horizons are followed by the bottoms of the S₁, S_2a, S_2b and L_1b horizons. A thin sandy soil developed in the lower part of the surface sand soil layer, FS, but there was no obvious development of an S₀ paleosol in the Middle Holocene. L₁, S₁, and S₂ possess the general characteristics of typical loess, and can be used as the marker beds of stratigraphic division and age control for the MLL section. The unique feature of the profile is manifested mainly in the higher content of sand in loess and paleosol layers. The sand(>63 μm) contents of loess and paleosol layers reach 57.11% and 44.77%, respectively, but no eolian sand is buried in the loess-paleosol layers. The cyclic variation of CaCO₃ in the loess and the paleosol layers of the MLL section was consistent with the Loess Plateau region, but opposite to that of arid desert regions. The CaCO₃ content in loess layers was significantly higher than that of the paleosol layers. Specifically, CaCO₃ contents in the well-developed S_2b and S_1b paleosol layers were only 0.13% and 1.31%, respectively. There were no obvious differences in magnetic susceptibilities between loess and paleosol, which reflected the relatively weak chemical weathering, but strong physical weathering, at the MLL loess-paleosol section. Strong winter monsoons, combined with eolian deposits, have caused the central Mu Us dune field to always behave as a sand plateau at Ordos Plateau since 245 ka B.P. Even in the warm-wet interglacial period, the intensity of summer monsoons was weak, as was the weathering and leaching of clay layers. This provides a new scientific basis for further research on environmental evolution of the central region in Mu Us dune field since the penultimate interglacial period.
Key words:Mu Us dune field/
loess-paleosol/
sedimentary characteristics/
stratigraphic division/
paleoenvironment



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