The Xiamen Symposium on Marine Environmental Sciences (XMAS 2025)

Holocene relative sea-level (RSL) data from the South China coast, a far-field location relative to polar ice sheets, have been used to infer ice-equivalent sea-level changes. However, there are notable misfits between geological RSL data and current glacial-isostatic adjustment (GIA) model predictions in the timing and amplitude of the mid-Holocene highstand and temporal variation of RSL over the Holocene. These misfits bring into question: 1) the interpretation and accuracy of proxies; and 2) whether other local- to regional-scale processes may have significantly influenced RSL.

Here, we present an updated, standardized Holocene RSL database with improved quality control. The dataset includes 227 index points and 342 limiting points, covering a geographical range from 119.19°E (Shantou, Guangdong Province) to 105.90°E (Red River Delta, Vietnam) and from 23.63°N (Chaozhou, Guangdong Province) to 16.45°N (Paracel Islands). Sedimentary (mangrove, tidal flat, lagoon), geomorphic (beach ridge, beach rock), fixed biological (oyster), and coral indicators comprise the majority of RSL data in the compilation for the last 12 ka. The database is divided into 10 sub-regions to investigate the influence of tectonics, sediment compaction, and GIA on RSL.

We apply a spatio-temporal empirical hierarchical model to the database to estimate magnitudes and rates of RSL and compare these results with GIA models using ICE-6G_C and ANU-ICE paired with the 3D earth model HetML140. Our findings reveal sub-regional variability on shorter spatial scales than the long-wavelength GIA signal throughout the Holocene. This spatial pattern suggests that some of the misfit with GIA model predictions stem from local- to regional-scale processes influencing RSL. Our analysis lays the foundation for assessing the potential influence of local factors such as sediment compaction and tidal range changes, as well as regional effects from tectonic vertical motion.
 

Holocene,Relative sea level,Sea-level change,Database