The tectonic characteristics of southern Helan Mountain and their relationships with the Guyuan-Qingtongxia fault
ZHANG Jin~(1),MA Zong-jin~(1),REN Wen-jun~(2) (1.School of Earth and Space Sciences, Peking University, Beijing100871,China;2.The Department of Geophysical Survey, Changqing Oil Field Company, Wuzhong751104,China)
The duration and processes of deformations in the southern and the central/northern Helan Mountains differ apparently. The location where the Guyuan-Qingtongxia fault crosses the Helan Mountain is determined in light of structures and stratigraphy. After crossing the Mountain the strike of the fault changes into E-W trending gradually. The authors think that the E-W trending structures in the central Ningxia may be a part of the fold-thrust belts which were formed during the early Paleozoic and were modified by later deformation. The Guyuan-Qingtongxia fault and the Yellow River fault controlled the development of the structures in the southern Helan Mountain and the massif (the Weining Beishan) confined by the two faults was moving eastwards in Cenozoic. In the eastern toe of the Weining Beishan the thrusting occurs; the reasons for the uplift of several mountains may lies in the eastward movement of the Weining Beishan.