AGE ASSIGNMENT OF THE "SANSHANZI LIMESTONE" IN WESTERN AND NORTHERN HENAN AND ITS GENETIC IMPLICATIONS

The "Sanshanzi limestone" is widely distributed in northern and western Henan. Its thickness is highly variable: it is the thinnest in Xinji, Lushan county, being only 28 m in thickness, while it is the thickest to the north in Rencun, Mianchi county, being 360 m thick. It is a complex geological body of dolomite. Its age varies from place to place, from the early Changxiaian age of the Middle Cambrian to the late Liangjiashanian age of the Early Ordovician. As a diachronous lithostratigraphic unit, it is an inclining mass of sedimentary rocks that formed in the process of marine regression during the Late Cambrian to Early Ordovician.