Evolution of the Mesozoic Yuljeon Basin in South Korea and its tectonic implication

Abstract

The Mesozoic Yuljeon Basin (YB) is a small scale non–marine sedimentary basin in the northeastern part of the Gyeonggi Massif in the Korean Peninsula. The YB consists of two lithostratigraphic units, the Munamdong and Yuljeon formations. Based on an integrated study of stratigraphy, structural geology, geochronology, and geochemistry, major episodes of the YB have been investigated. In the late Triassic (after 227 Ma), the YB was formed in a tectonic setting, wherein crust was extended and uplifted, which resulted in deposition of the Munamdong Formation. In the latest early Jurassic (circa 180 Ma), the Yuljeon Formation was deposited in association with volcanic activity in a continental magmatic arc setting. On entering the middle Jurassic (circa 174 Ma), extension in the YB stopped and then basin inversion occurred due to contractional deformation. The middle Jurassic thermal pulse in the area generated various scale igneous rocks and induced hydrothermal circulations, which created suitable conditions for fault activity with help of fluid pressure. This study demonstrates that the YB formed with sedimentation in a post–collisional extensional setting related to the Songrim Orogeny, and then it was enlarged with volcanic–related sedimentation in a continental arc setting related to the Daebo Orogeny, and lastly it was followed by basin inversion with arc magmatism in the same continental arc setting, reflecting the temporal and spatial changes in regional tectonics. Moreover, the general provenance characteristics for the early Mesozoic strata in the eastern North China Block, Gyeonggi Massif of South Korea, and southwest Japan, can be geochronologically correlated. The sedimentary rocks record the distinctive tectonothermal histories of East Asia such as the middle Paleoproterozoic orogens in the eastern North China Block, the Permo–Triassic continental collision between North and South China Blocks, and the subduction of Paleo–Pacific plate during the Mesozoic.