STRATIGRAPHIC SEQUENCE AND AGE OF THE CONGLOMERATIC LIMESTONE AND ITS RELATION WITH THE ADJACENT STRATA ON THE NORTHERN SLOPE OF THE EASTERN QINLING
东秦岭北坡含砾灰岩层位、时代、沉积环境及其与陶湾群等地层的关系

This paper deals with stratigraphic sequence and age of the conglomeratic limestone and its sedimentary environment on the northern slope of the eastern Qinling (Shangxian, Luonan, Lushi and Luanchuan), and discusses the relationship between the conglomeratic limestone and adjacent strata. The conclusions are as follows:1. The conglomeratic limesotne of the Sanchakou Formation lies conformably on the Dazhuang Formation and unconformably under the Luoquan Formation, and therefore, the Sanchakou Formation is older than the Luoquan Formation. 2. Because the conglomeratic limestone lies unconformably on the different Strata of the Taowan Group, it can not be considered as part of the Taowan Group. 3. The conglomeratic limestone was deposited in a trough of the inner side of the Qinling island arc, and therefore, the pebbles of this formation came from the island arc in stead of the Sino-Korean palaeocontinent. According to the distribution of the pebbles, this arc stretched discontinuously 200 km long and was one of the marginal arcs along the palaeo-continent. The conglomeratic limestone intercalated in the Dazhuang Formation settled in the inner side of the Qinling island arc too. 4. According to the analysis of deformational periods, the conglomeratic limestone of Shanchakou Formation in Shangxian district is older than the Cambrian strata around. 5. The Dazhuang Formation is dated 562 + 31 m. y. (Rb-Sr whole rock isochron). 6. The Dazhuang Formation and Sanchakou Formation are considered to be the lower formation of the Luanchuan Group,which may be part of the Sinian system on the northern slope of the eastern Qinling.