Soluble salt deposition of the Dunhuang yardang strata and its indication for sedimentary environment
The yardang strata is the material manifestation of the sedimentary system before the yardang land-form developed.It records a large amount of surface process information such as sedimentation processes,envi-ronmental evolution,and landform patterns.The physical and chemical analysis of sediments has become an im-portant prerequisite for interpreting its key information.As an important environmental proxy index,the charac-teristics of easily soluble salts have important significance in interpreting the sedimentary evolution process of the yardang Formation.This paper takes Dunhuang yardang landforms as the research object,and conducts an in-depth discussion on the soluble salt deposition characteristic,environmental proxy indicators and sedimentary en-vironment evolution of its exposed strata.The results indicated that:(1)The dominant ions'composition of solu-ble salts in yardang sediments is characterized by the combination of Mg2+-Na+-Ca2+-Cl--SO4-,and the corre-sponding ion types mainly include Cl-Na type and SO4-Ca-Mg type.(2)The main ions and the total salt content in the studied profiles have significant vertical cycle variation characteristics,mainly dominated by the alternat-ing changes of sulfate and chloride salts,both of which play a decisive role in controlling the deposition of yard-ang soluble salts.(3)Environmental proxies such as Mg2+/Ca2+and Cl-/SO42-have certain limitations in the differ-entiating of yardang environmental changes,indicating that yardang strata were not entirely developed from sta-ble lacustrine deposition.(4)The yardang formation is the result of alternate deposition of various materials formed under different sedimentary environments and dynamic mechanisms,which mainly includes stable lacus-trine,lakefront,fluvial,aeolian and alluvial fan's mud flat materials.Among them,lakefront,fluvial and aeoli-an sediments have similar physical and chemical properties,making it difficult to distinguish in detail and need further study.
NETL
NSTL
万方数据
