Establishment of Quaternary Section and Its Environmental Significance in Yanji City

摘要

According to the landform location, lithology and lithofacies features, special interlayer, geological age and pollen analysis of sediment distribution, this paper ensured the deposition sequence and formation age of Quaternary deposition in Yanji basin, and explored the evaluation progress of the regional paleogeography environment. Results showed that: (1) After analyzing the shear wave velocity and section of both HDBZK-2 and HDBZK-3 respectively, it was found that vse of Cretaceous was far bigger than vse of Quaternary; (2) The Quaternary section of Yanji basin was divided into two segments. Holocene deposit (0-4m): it was typical river sediment. Late Pleistocene deposit (4-13.5m): it was typical river sediment, which was equivalent to the sediments in the last glaciation; (3) According to field geological investigation, the late period of Holocene deposit was mainly distributed in floodplain and riverbed, and the lithology was mainly gravel, sand and clay. The middle Pleistocene deposit was mainly distributed at the third terrace of Buerhatong River and its branches. The bottom was gravel layer and the top was sand and clay layer; (4) Since the late period of the late Pleistocene, the regional climate has experienced a cycle of relatively cold, dry cold, relatively cold, dry cold, relatively cold and wet humid.