Age and relative uplift of marine terraces controlled by fault activities along the eastern coast of Korea

A comprehensive examination of uplifted mid-late Pleistocene marine terraces along the eastern coast of Korea offers valuable insights into the temporal and spatial variability of uplift rates spanning ∼200 ka. Focusing on the Gangneung–Samcheok region of the Korean peninsula’s east coast, the study area is delineated into three distinct areas (i.e., Anin, Jeongdongjin–Donghae, and Samcheok) by two NNE-SSW to NE-SE-striking faults. Three flights of marine terraces are developed in each area, with terraces typically observed at elevations of 10 to 20 m and 20 to 35 m across all three areas. Conversely, upper terraces exceeding these elevations are mainly observed at 50 to 60 m or 60 to 80 m, with regional variations noted. Quartz optically stimulated luminescence dating (OSL) was used for dating marine terrace deposits. However, it could not be applied to older deposits beyond the upper limit of quartz OSL. Therefore, IRSL and post IR-IRSL dating using K-rich feldspar, which has a higher upper limit than quartz OSL, were applied in this study. The results indicate that marine terraces at elevations of 10 to 20 m and 20 to 35 m formed during MIS 5a and MIS 5e. Depositional ages of MIS 7 were obtained from terraces ranging from 50 to 60 m or 60 to 80 m, exhibiting elevation differences across regions. Consequently, the estimated temporal variation in uplift rates revealed an average uplift rate of 0.52–0.79 m/ka from MIS 7 to MIS 5e, followed by 0.2–0.3 m/ka after MIS 5e. Spatial variation in uplift rates was observed from MIS 7 to MIS 5e. Specifically, the uplift rate in the Jeongdongjin–Donghae area, located in the middle part of the study area, was 0.79 m/ka (Min. 0.68 m/ka, Max. 0.90 m/ka), whereas the uplift rate in the other study areas was 0.52 m/ka (Min. 0.41 m/ka, Max. 0.62 m/ka). This discrepancy is probably attributed to the influence of the two faults that subdivide the study area.