Radiocarbon is the most common method used for dating sediment chronology, especially for lacustrine sediment. However, the ubiquitous Radiocarbon Reservoir Effect hinders the accuracy of lacustrine sediment chronology. Although massive research have studied the Radiocarbon Reservoir Effect in temporal and spatial, fewer studies focus on the Radiocarbon Reservoir Effect and the depositional process. Here we gave particular attention on the Lop Nur, which is the largest playas Located in Central Asia. And the climatic evolutionary process of Lop Nur is tightly bounded up with the Asian inland drying evolution and human activities along the ancient Silk Road. Previous studies have given an ambiguous chronology and large lake reservoir age from different drill due to the complex sediment process. Here, a 1.3m long pits at the top of the Big Ear area was sampled to conduct sedimentological and high-precision chronology studies. We found that grain size changes in Lop Nur sediment correlated with the fluctuation of the radiocarbon age. Taking the apparent sedimentary phase transition at 58cm as the boundary, the coarser particles contain less TOC, and have younger age. Our results suggest that the Radiocarbon reservoir effect of Lop Nur, as the convergence center of rivers in Tarim Basin, is mainly affected by exogenous organic carbon input. In the wetting stage, lacustrine clay adsorbed more old organic matter from the erosion area in upstream of the river. On the contrary, the organic matter carried by aeolian sand in the drought period is limited, resulting in 14C age anomalies.

radiocarbon,Lacustrine sediments,reservoir effects,organic matter