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Arid Land Geography ›› 2023, Vol. 46 ›› Issue (11): 1826-1835.doi: 10.12118/j.issn.1000-6060.2023.083

• Earth Surface Process • Previous Articles     Next Articles

Characteristics of grain size and geochemical elements composition of surface sediments of megaripple stripes in the Qaidam Basin

WANG Lijie(),XIAO Fengjun(),DONG Zhibao,MA Huirong,CHEN Hao   

  1. School of Geography and Tourism, Shaanxi Normal University, Xi’an 710119, Shaanxi, China
  • Received:2023-02-25 Revised:2023-04-21 Online:2023-11-25 Published:2023-12-05

Abstract:

Megaripple stripes (MRS) are an enigmatic eolian bedform pattern characterized by alternating megaripples corridor (MRC) and smaller bedform corridor (SBC), oriented crosswise to the prevailing wind direction. MRCs have taller bedforms, longer wavelengths, and coarser surface sediments compared with the intervening SBCs. MRSs are widely distributed across the middle and southern margins of the Qaidam Basin, Qinghai Province of China, but their comprehensive study remains limited. Analyzing MRS surface sediments can provide a reference for the subsequent study on its formation and evolution, along with the erosion and deposition processes of eolian sand. Herein, 112 surface sediment samples were collected from the middle and southern margins of the Qaidam Basin. The physical (grain size characteristics) and chemical properties (major and trace elements) of these sediment samples were analyzed. The results of this study are as follows: (1) MRCs primarily consist of gravel and very fine sand, with gravel and very fine sand contents ranging from 44.24% to 50.19% and 15.91% to 20.42%. The grain size frequency curve of MRCs shows a bimodal distribution. Conversely, SBCs are primarily composed of very coarse and fine sands, varying from 26.00% to 35.90% and 14.80% to 20.47%. The grain size frequency curve of SBCs shows a trimodal distribution. (2) MRS sorting parameters are poor and exhibit positive and negative skewness but primarily positive skewness. MRS kurtosis is relatively wide to very wide. (3) There are no considerable differences in the content of chemical elements between MRCs and SBCs. The major elements of MRS primarily consist of SiO2 and Al2O3, with the highest SiO2 content of ~63% and Al2O3 content hovering at ~10%. The trace elements, such as Cr, Co, Mo, and Ba, play a dominant role compared to the upper continental crust, Cr and Mo elements show an enriched state, while other elements show signs of leaching. (4) MRS sedimentary environment in the middle and southern margin of the Qaidam Basin is cold and dry. These areas have experienced low chemical weathering, with relatively stable chemical weathering. Compositionally, they closely resemble the upper continental crust and are in the early stage of continental weathering.

Key words: megaripple stripes, Qaidam Basin, sediments, grain size, chemical elements