Kim Chaek University of Technology Pyongyang 999093 Korea;
School of Earth Sciences China University of Geosciences(Wuhan) Wuhan 430074 ChinaState Key Laboratory of Biogeology and Environmental Geology China University of Geosciences(Wuhan) Wuhan 430074 China;
Kim Chaek University of Technology Pyongyang 999093 Korea;
clay minerals; crystallinity; loess-palaeosol; origin; polytype;