PRELIMINARY STUDY OF GEOLOGY AND GEOMORPHOLOGY OF LUONAN BASIN

Luonan Basin, formed during Neo\|tectonic movements, is one of the small block basins in East Qinling Mountain. Three faults, Tieluzi Fault, Dajing\|Guojiayuan Fault and Beisi Fault bound it. The west part of the basin is higher than the east part. The elevation, usually more than 1100meters in the west, decreases gradually to less than 800meters in the east. The Cenozoic deposit in Luonan Basin is thin in the west part and becomes increasingly thick towards the east part. The total thickness of both the Eogene and the Neogene is only more than 100meters at Dajing. At Duishan, a place close to Luonan county town, it is about 400meters, and at Gucheng, it becomes nearly 1750meters. The strata crop out in the west part of the basin, usually the Eogene and the Neogene, are older than those in the east part which are usually the Quaternary deposits. The pattern of the Cenozoic deposits in Luonan Basin is similar to that in Shangzhou Basin (Li Kaoshe, personal communication), a basin locating just to the south of Luonan Basin.