High-precision radiocarbon dating and carbon reservoir effect of a maar lake in South China

Abstract

High-resolution maar lake records with robust age control provide an ideal foundation for investigating paleoclimate change. However, in tropical-subtropical South China, the carbon reservoir effect of lake sediments is poorly understood, resulting in a lack of high precision records, hindering the comprehensive understanding of regional climate change and its forcing mechanism. In this study, based on a newly drilled core from the Tianyang (TY) maar lake located in South China, we conducted detailed radiocarbon dating of various materials to assess the reservoir effect and establish a reliable high-resolution chronology of the maar lake. Comparing radiocarbon ages of different grainsize and different fractions, the ages of bulk samples were closest to those of plant remains or charcoals which we consider as the reliable dating materials. Pairs of bulk samples and plant remain or charcoal ages indicate a limited but variable reservoir effect in TY maar lake. The reservoir effect is negligible from the surface to 623 cm (0–30.95 ka) and then gradually increased from negligible to approximately 700 years between the depth of 623–747 cm (30.95–37.15 ka). We hypothesize that the reservoir effect in the deeper part of the lake results from a combination of longer mean residence time due to lower sedimentation rates and increased groundwater level, which is linked to higher sea levels during the marine isotope stage 3 (MIS3). After reservoir correction, Bayesian age-depth modelling was performed based on 53 reliable radiocarbon ages, achieving a high-resolution chronology of TY maar lake covering the past ∼37 ka period with a mean age model uncertainty of 357 years, providing a reliable dating framework for paleoclimate reconstruction.