Sedimentary environmental evolution of the Dalinghe Estuary area since the Late Middle Pleistocene

The comprehensive studies of sedimentology, micropaleontology and chronology of borehole LZK06 at 40m depth and combined with the data of boreholes LZK02-04 in the Dalinghe estuary area revealed that the study area experienced two transgression-regressions since the Late Middle Pleistocene, and the Late Middle Pleistocene lacustrine/fluvial Late Pleistocene marine lacustrine/fluvial Holocene marine fluvial stratums were sequentially formed. In the Early and Middle Holocene, due to the lower source supply, the study area was in a 10 ka long phase of starving deposition environment with an average sedimentary rate of 0.02~0.05 cm/a. In the Late Holocene, about 1500 years ago, due to the human activities leading to soil erosion and increased sediment transport in the river, the study area began a rapid accretion process with an average sedimentary rate of 0.9~1.2 cm/a, and the lower Liaohe plain was quickly filled. Compared with the tempo-spatial pattern of global sea level change, it is speculated that the marine bed II was formed in MIS 5-early MIS 3 and marine bed I was formed in MIS 1. Frequent sea level change is the main controlling factor for stratigraphic and environmental evolution in the muddy coast of Liaodong Bay since the Late Pleistocene. © 2020, Science Press. All right reserved.