Acta Geographica Sinica ›› 2017, Vol. 72 ›› Issue (2): 279-291.doi: 10.11821/dlxb201702008

• Land Use and Environmental Change • Previous Articles     Next Articles

Chemical weathering characteristics and regional comparative study of the loess deposits in the upper Hanjiang River

Peini MAO(), Jiangli PANG(), Chunchang HUANG, Xiaochun ZHA, Yali ZHOU, Yongqiang GUO, Hui HU, Tao LIU   

  1. College of Tourism and Environmental Sciences, Shaanxi Normal University, Xi'an 710119, China
  • Received:2016-06-17 Revised:2016-10-12 Online:2017-02-15 Published:2017-02-15
  • Supported by:
    National Natural Science Foundation of China, No.41271108, No.41371029, No.41471071;National Social Science Foundation of China, No.14BZS070;The Fundamental Research Funds for the Central Universities, No.GK201704014

Abstract:

Field investigations were carried out along the upper reaches of the Hanjiang River, a major tributary of the Yangtze River in China. Three loess profiles on the first river terrace were selected for a detailed study. The characteristics of major elements and chemical weathering were analyzed systematically. Results are shown as follows. (1) The major elements are dominated by SiO2, Al2O3 and Fe2O3, the total average content of which is 767. 3 g/kg, in the loess profiles of the region. The contents of the major elements are ranked in the following order: SiO2>Al2O3>Fe2O3>K2O>MgO>Na2O>CaO. The elements Na, Ca, Mg and Si are leached to different degrees and Fe, Al and K relatively enriched in the chemical weathering processes. (2) The weathering and pedogenic intensity was the weakest in the Malan loess L1, increased slightly in the transition loess Lt, became the strongest in the paleosol S0, and decreased again in recent loess L0. The results reveal that the climate was cold-dry in the Last Glacial (55.0-15.0 ka BP), turned into warm-wet gradually in the Early Holocene (15.0-8.5 ka BP), became the warmest and wettest in the Mid-Holocene Climate Optimum (8.5-3.1 ka BP), and turned into cool and dry in the Late Holocene (3.1-0.0 ka BP). (3) Based on the comparison with Luochuan, Wushan and Xiashu loess, we can find that the major elemental compositions and the UCC-normalized patterns of the loess are similar with those of Luochuan, Wushan and Xiashu loess to a higher degree, suggesting a similar sedimentary background of aeolian loess. But the chemical weathering intensity of these loess deposits changes significantly in different parts of China, with the sequence?of Luochuan loess < loess in the Hanjiang River < Wushan loess

Key words: loess, major element, chemical weathering degree, upper Hanjiang River, regional comparison