Radiocarbon chronology of sediments with implications for climatic events in Lop Nur, NW China

Abstract

Radiocarbon dating has played a pivotal role in paleoclimate research, particularly in establishing chronological sequences for lake sediment. However, the persistent challenge of the radiocarbon reservoir effect has remained a notable concern when using 14C dating. While several methods have been developed address this issue, the spatiotemporal variability of the lake reservoir and their climatic implications on the occurrence of anomalous 14C dating results have frequently been overlooked in previous studies. Especially when dealing with lake sediments in arid regions of Central Asia, the impact of climate-induced sediment sources and watershed hydrology poses substantial challenges for 14C dating. In this study, we focused on sediment profile in the Lop Nur and established a reliable chronological framework for the late Holocene using a piecewise linear regression approach. By integrating climate data from the surrounding region and archaeological evidence, we reconstructed the hydrological and aeolian processes of Lop Nur spanning from 670 BCE to 1300 CE. Our findings suggest that the anomalies observed in dating results were closely associated with the presence of sand component with a reduced organic matter content. And the record reveals the occurrence of sandstorm events around 500 BCE and 300 BCE, with a significant increase in strength after 200 CE. This indicates a decrease in reservoir effects during the lake regression, due to increased aeolian inputs. Therefore, we proposed that the deposition of larger-sized sandstorm particles during lake regression is predominant reason for reduced absorption of surrounding aged organic matter, leading to the younger age observed.