Stratigraphic Response to Tectonic Evolution of the Cretaceous Gyeongsang Basin, Korea: An Example of Tectonically Controlled Lake Basin in Active Margin Setting

Ryu, In-Chang¹, Seon-Gyu Choi², Soo-Meen Wee³, Tae-Hoon Kim⁴, Chang-Yoon Lee⁵ (1) Kyungpook National University, Daegu, South Korea (2) Korea University, Seoul, South Korea (3) Korea National University of Education, Cheongju, (4) Kyungpook National University, Department of Geology, Daegu, South Korea (5) Kyungpook National University, Department of Geology, Daegu, Korea, South Korea

The Cretaceous Gyeongsang Basin, onshore southeastern Korea, comprises more than 9,000 m of siliciclastic and volcanic strata that were deposited in a lake basin in active continental margin setting. Detailed stratigraphic, sedimentologic, and paleontologic data are integrated to make a coherent stratigraphic framework in the basin. A newly proposed integrated stratigraphic framework indicates that strata in the basin can be subdivided into five distinct stratigraphic units that represent pre-rifting, syn-rifting, inversion I, II, and III stages. The Gyeongsang Basin was formed as a lake basin during the Early Cretaceous. In the Late Cretaceous, however, the basin was deformed by three-staged sequential deformation of north-south, northwest-southeast, and east-west compressions. The formation and deformation of the basin has been largely controlled by the change of motion of the Izanagi Plate from north to northwest during the Cretaceous. In the early Cretaceous, the Izanagi Plate began to subduct northward beneath the Eurasian Plate and caused the left-lateral strike-slip fault systems in the southeastern part of the Korean Peninsula. The left-lateral wrenching of these fault systems was causally linked to development of lake basins in the southeastern part of the peninsula. However, northwestward movement of the Izanagi Plate during the Late Cretaceous probably led to the extensive volcanism and sequential deformations in the basin. Together with the spatial and temporal correlation of the Cretaceous basins in adjacent areas, this stratigraphic and tectonic model of the Gyeongsang Basin provides a new geologic paradigm to delineate the sophisticated tectonic history of East Asia during the Cretaceous.