Reconstruction of Holocene coastal progradation on the east coast of Korea based on OSL dating and GPR surveys of beach-foredune ridges

Abstract

Coastal dunefields along the east coast of Korea have long been thought to have originated from beach ridges that prograded during the Holocene, but there has been little chronological evidence based on absolute dating. In this paper, we use optically stimulated luminescence (OSL) dating and ground-penetrating radar (GPR) surveys to reconstruct the coastal progradation of Anin dunefield in the Gangneung area on the east coast of Korea. GPR profiles and sedimentological analyses of four beach-foredune ridges reveal that the ridges are composed mainly of beach deposits showing seaward-dipping and horizontal laminae, capped by eolian sands with landward-dipping laminae. The beach deposits are, in places, underlain by fluvial sands with gravels. Coupled with data from OSL dating, we interpret these results to mean that the fluvial sands and rounded cobbles were deposited in the study area, during the last glacial period. Between the mid-Holocene (~6.5 kyr) and c. 3.5–3.0 kyr, the transgression rate of the sea decreased and coastal progradation occurred. Between c. 3.5 and 3.0 kyr, foreshore sediments, including granules and pebbles, accumulated over the older beach deposits, indicating erosional events. Progradation resumed at ~3.0 kyr and continues to the present. During the past 3 kyr, there has been an average rate of progradation of ~0.14 m/yr. The beach-foredune ridges in the Gangneung area represent the evolution of coastal progradation on the east coast of Korea during the Holocene.