Abstract: Background, aim, and Scope Chronology is vital for studying the Late Quaternary coastal geomorphology and the land-sea interaction. In this study, we aimed to analyze the chronological characteristics of sediments in the Yangtze River delta based on the dataset of collections from our previous two cores’ sedimentary records and from other cores’ records recently reported in the adjacent areas. We attempt to illustrate the spatiotemporal features of the Yangtze River delta sedimentary evolution since MIS3 in the scope of chronostratigraphic investigations. Materials and methods In current study, we synthesized several chronological sequences according to the dataset of 50 ages from our previous published two cores (YZ07 and EGQD14) in the Yangtze River delta together with a few ages from other cores in the adjacent areas. Each age determined by quartz OSL dating techniques in the dataset is re-examined through the critical items, including characteristics of OSL signals, the IR-OSL depletion ratios, as well as the dose rates. Results Combing our recent studies with the relevant archives from the adjacent cores, we re-analyzed its sedimentary environment changes and coast dynamics since MIS3. It tended to show that a terrestrial-dominated environment happened at MIS3, a depositional hiatus occurred in LGM and variable patterns existed in the Holocene. Discussion Finer quartz grains, e.g., 4—11μm or 63—100 μm, would be much better than that of 100—200 μm in routine OSL dating, as the later might suffer from feldspar inclusions and resulted in OSL ages underestimation. Fortunately, the problem could be resolved by using the pulsed OSL dating technique. Comparison of the chronologies between OSL and radiocarbon dating, it shows that 14C ages are severe inversion against with the stratigraphic sequence while OSL ages display a well correlation with the strata. Therefore, we suggest to combining the two dating techniques for coastal-deltaic deposits. Conclusions New chronological evidence of core EGQD14 reveals that a fluvial dominated sedimentary environment happened during MIS3 (30—50 ka). Similar conclusions were set up on the records from the adjacent cores. A deposition hiatus occurred due to the decline of sea level and the formation of the incised valley during the LGM. In the Holocene, the incised-valley underwent stacking with the accommodation variation as sea level changes. In these processes, the Yangtze River delta initiated and gradually developed seaward. The accumulation rate is characterized with three periods, namely to be fast deposition in the early Holocene and in the late Holocene (~2 ka to 0 ka) but relative slow sedimentation during the mid-to-late Holocene. Recommendations and perspectivesHowever, the chronological framework of the strata in the Yangtze River delta beyond MIS3 is still poor so far. In the future, we should pay more attention to the sedimentary stratigraphy of the last glaciation using more newfangled luminescence dating techniques (e.g., K-feldspar and/or polymineral post-IR IRSL dating).
Keywords: Late Quaternary; Yangtze River delta; land-sea interaction; quartz OSL dating