Detrital zircon geochronology of the Cretaceous Sindong Group, Gyeongsang Basin, Korea and its implications for paleodrainage systems

The Lower Cretaceous Sindong Group in southeastern Korea is a fluvio-lacustrine sedimentary package deposited in an elongated basin formed by extension in an active continental margin setting. To characterize its changes in paleodrainage system, we analyzed U-Pb ages of detrital zircons in sandstones from each stratigraphic units in northern, central, and southern parts of the Sindong Group. Detrital zircons show a wide range of ages from 106 Ma to 3494 Ma with spatiotemporal variations in age population. Detrital zircon age spectra and paleocurrent data reveal that at least three drainage basins sourced to the Early Cretaceous river system in the Yeongnam Massif. The drainage system for the central portion of the basin was consistent with time, whereas those for the northern and southern portions shifted between the Nakdong Formation and Hasandong Formation. The strong influences resulting from the confluence of dispersal path draining Jurassic granitoids, possibly aided by faulting activity, likely caused the replacement of paleodrainage system in the northern portion. The drainage system of the southern portion was changed by extension of the drainage basin to the source terrane having similar geology to or shared the source terrane for the paleoflow system for the central portion.