Holocene environmental evolution history based on sporopollenin and micropaleontological reconstruction of KY-01 in the Yellow River Delta

The Yellow River Delta adjacent to the Bohai Sea is located in the monsoon region of northern China, which is sensitive to global climate change. The core data of KY-01 borehole in the Yellow River Delta and the published records were used to reconstruct the climate environment. Based on the analysis of carbonate content, magnetic susceptibility, Ostracoda, foraminifera, sporopollenin and AMS C-14 dating on the KY-01 borehole sediment core, the evolution of both the climate and sedimentary environment has been discussed. The results show that: 7656-4145 cal.aBP, seawater moved toward the land surface and the climate was generally warm and humid, when there were small-scale extreme climate fluctuations; 4145-2544 cal.aBP, transgression and recession occurred, the climate changed from warm-wet to dry-cold and there were small-scale extreme climatic events; and 2544 cal.aBP-1855 AD, the sea level was relatively low, transgression and retreat alternately occurred, the climate was drier and colder than the previous stage and the warming and cooling alternated. During the middle Holocene, cold-dry events occurred between 5737-5422 and 4451-4081 cal.aBP, which is consistent with both Chinese and worldwide climate records.