# Study on Sedimentary Evolution of the Hanjiang River Delta during the Late Quaternary
###### Abstract  
In recent years, coastal areas have been threatened by many potential hazards due to global warming, glacier melting and sea level rise. Understanding their evolutionary history and development trends can help predict disasters and further reduce the corresponding losses. The Hanjiang River delta in the southeastern part of China is the second largest delta in Guangdong Province and has such challenges. Studying the sedimentary evolution and delta initiation of the Hanjiang Delta is beneficial for understanding the response of the Hanjiang Delta to present and future sea level and climate changes. In this research, we drilled a series of cores from the Hanjiang subaqueous delta, which contains information on the sedimentary environment, climate change and sea level change during the late Quaternary. Combined with previous research results and under the constraint of high-precision and high-resolution AMS\({}^{4}\)C and OSL, we carried out a multi-proxy analysis that included micropleaontology and grain size to obtain information on the sedimentary environment, sea level change and climate change. We then further discussed the initiation of the Hanjiang delta and its primary factors. The Quaternary sediments began depositing in the early Late Pleistocene (MIS5), and three sedimentary cycles can be recognized from bottom to top. The dating results also indicate that the first two cycles were formed during the late Pleistocene, while the last cycle was formed during the Holocene. The initiation of the Hanjiang Delta was indicated by a programation in the process of a transition from estuary to a typical delta. At this time, the rate of delta degradation seaward was fast, and increasing amounts of sediments moved through the third line of islands into the sea. The barrier-lagoon system began to develop in the estuary of Hanjiang during this period. With the sequential construction of the delta, the lagoon was filled and covered by delta deposition, and the barrier bar moved to the sea; thus, the barrier-coast delta depositional model was established in the study area. Since the last glacial period (LGM), the Hanjiang River Delta and other river deltas in the region seem to have experienced similar evolutionary histories, including the filling of incised paleo-valleys and estuaries in the Early Holocene and deltaic degradation in the Middle to Late Holocene, controlled by sea level change. H 2023 2  
River, Yangtze River, Pearl River, Red River and Mekong River, have been comprehensively studied. However, the small- and medium-sized river deltas in this area have received less attention. The Hanjiang River Delta is a typical representative of the medium-sized river delta in East Asia. Therefore, an analysis of the late Quaternary sedimentary evolution process of the Hanjiang River Delta can provide representative geological information as a reference for the study of late Quaternary sedimentary records, sea level and climate change in small- and medium-sized estuary deltas and their adjacent continental shelf areas. The study of deltas can be traced back to the end of the 19 th century. [PERSON] (1975) divided the world's major river deltas into three categories: the Mississippi River Delta, which represents river-dominated deltas; the San Francisco River delta in Brazil and the Senegal River Delta in Africa, which represent wave-dominated deltas; and the Ganges Delta and the Basheng-Langa River Delta in Malaysia, which represent tidal-dominated deltas [4]. Since the middle and late 20 th century, the concepts of chronology and sequence stratigraphy have been widely used and developed in geology. With the deepening of human research on Earth system science, the stratigraphic structure and sedimentary evolution of postglacial river deltas have become the focus attention of scholars [1]. The latest research suggests that global climate and sea level changes have a certain unity, though regional characteristics can be found [5].