Stratigraphic and chronological characteristics of Shidao Island within the Xisha Islands, South China Sea, and its response to sea‐level changes since the Late Pleistocene

Abstract

Sedimentological and chronological analyses of coastal dunes can determine their sedimentation processes and yield information that can reflect changes in local marine environments (e.g., information on climate, biology, and sea-level changes in tectonically stable areas). In this study, Late Quaternary deposits on Shidao Island, one of the Xisha Islands, South China Sea, were analysed using techniques such as U/Th dating to obtain the following results: (1) Four lithofacies associations and two unconformities were identified from the deposits on Shidao Island.On this basis, the Shidao Island sediments can be divided into three stages of aeolian sediments and one stage of beach rock sediments. (2) U/Th dating revealed that the aeolian deposits on Shidao Island formed during three periods, namely, marine isotope stages 5.2, 5.1, and 4, and that the beachrocks were formed in the Holocene when the sea level rose to its present height. (3) The aeolianites on Shidao Island all formed in an environment in which the sea level was relatively stable or slowly falling. This study determined for the first time the specific sedimentary ages of the aeolianites on Shidao Island, and reconstructed the sedimentation process of the deposits on Shidao Island based on palaeo-sealevel changes. These results can provide more reliable geochronology data for the future study of Late Quaternary marine environments across the East Asian region.