Late Pleistocene to Holocene sedimentary history in the Pearl River Delta revealed by OSL and radiocarbon dating

Abstract

A reliable chronology is essential to understand deltaic sedimentation processes in response to sea-level fluctuations and climatic changes. In the Pearl River Delta (PRD), high-resolution chronostratigraphy is still limited which hinders the detailed interpretation of sedimentary history. In this study, optically stimulated luminescence (OSL) dating and radiocarbon (14C) dating were applied to establish a chronological framework of core P5-4 (30 m depth) in the southern PRD. Fifteen OSL and four 14C samples produced ages ranging from c. 8 ka to 0.5 ka, and two older OSL samples produced minimum ages of 75 and 62 ka. 14C ages are generally older (up to c. 1 ka) than the corresponding OSL ages and the discrepancy increases with depth. The ages and sedimentary data of sixteen published cores have been compiled to correlate the regional stratigraphy and reconstruct the late Pleistocene to Holocene deltaic process. It is concluded that: (1) The bottom subaerially-exposed deposits of core P5-4 were dated to marine isotope stage (MIS) 5, which is consistent with similar OSL-based records in the PRD. The laterally correlation shows that a depositional hiatus during c. 70–8 ka prevailed in the PRD and may attribute to strong erosion due to weathering and fluvial scouring. (2) Due to the relatively high altitude of bedrock, the post-glacial marine deposition of the PRD started at c. 8 ka, postdating other megadeltas by at least 2–4 ka. During 8–0.5 ka, a three-stage sedimentary process that is common in the PRD occurred in P5-4, i.e., early-Holocene (8–6 ka) rapid accumulation rate (5.44 m/ka) associated with rapid sea level rise, followed by mid-Holocene (6–3 ka) decelerated sedimentation rate (1.17 m/ka) in response to reduced sediment supply and strong tidal forces and late-Holocene (3–0.5 ka) accelerated sedimentation rate (2.28 m/ka) due to enhanced human activity.