Abstract:
Based on the systematic analysis with the Yan'an forma-tion in Rujigou area of the remnants stratum distribution,coal formation characteristics,strata sequence classification and correlation,sedimentary environment,material sources and Palaeo-flow direction,stress pattern and so on,com-bined with the basic geological features in north of western margin of Ordos basin,the relationship between Rujigou are-a and Ordos basin has been discussed in this paper. At the same time,the presence of alluvial fan sediments in Rujigou region indicated that the area had been close to the north-western edge of the ancient Ordos basin. There is no obvious geological split between Rujigou area and Ordos basin in Yan 'an age of Mid-Jurassic. The comprehensive analysis showed that Rujigou area is a part of Ordos Basin near to the northern margin and topography declined slowly from west to east,the western margin fault of Helan Mountain is the northwest sedimentary boundary of Ordos basin in Yan'an age.