Chronostratigraphic implication of the Yucheon Group in Gyeongsang basin, Korea

Based on the reliable absolute chronological data measured in the Yucheon Group, Gyeongsang Basin, the chronostratigraphic implication for the lithostratigraphy was investigated. The Yucheon Group can be largely divided into the Jusasan, Unmunsa, Yokji and Saryang subgroups by lithostratigraphy, which can be correlated with chronostratigraphic implication from the age ranges of each subgroup by zircon age data. In the central and southern parts of the Yucheon Subbasin, the eruption age of the Jusasan Subgroup ranges from 94.4 to 88.8 Ma, which correspond to the Turonian. And the eruption age of the Unmunsa Subgroup in the same areas show a range of 88.9 to 80.4 Ma, which corresponds to the Coniacian to the early Campanian. Meanwhile, the activity period of the Yokji Subgroup ranges from 78.4 Ma to 73.0 Ma, corresponding to late Campanian, if the U-Pb age of 78.40 Ma measured in the central part and 73.01 Ma in the southern part of the Yucheon Subbasin are regarded as the lower and upper limits, respectively. The active period of the Saryang Subgroup, from 71.7 to 60.1 Ma age, which corresponds to the Maastrichtian to Selandian, based on the combined data in the southern part of the Yucheon Subbasin, and in Uiseong and Yeongyang subbasins. It is expected that the classification of subgroups based on the chronostratigraphy can be utilized for stratigraphic correlation in the Yucheon Group.