Paleoclimate Changes Of Holocene In The Daling River Basin

The Liaohe River Delta is a multi-river delta in northeastern China,among which the Daling River has the largest sediment transport capacity.However,its contribution to the Liaohe River Delta is often underestimated.It is of great significance to explore the evolution of sedimentary environment of the Daling River Estuary since the Holocene.Exploring the paleoclimate change and sedimentary facies evolution of the Daling River Basin during Holocene is helpful to improve the research on the sedimentary rate and paleoclimate of the Daling River Basin.In this paper,through the OSL and 14 C dating,grain size,clay minerals and geochemical methods,the sediment samples of Daling River were comprehensively analyzed,and the discriminant index of clay minerals and elements ratio suitable for this area was extracted.On this basis,the paleoclimate change of Daling River Basin since Holocene is analyzed,and the deposition rate is discussed.The main understandings are as follows:1.NQ-1 hole is divided into three sedimentary sections of U1-U3 from bottom to top,namely U1 fluvial facies channel subfacies,U2 estuarine facies and U3 delta facies,and U3 section is further divided into three sedimentary layers of U31,U32 and U33 from bottom to top,which correspond to the pre-delta facies,delta front facies and delta plain facies respectively.2.The average sedimentation rate of NQ-1 hole sediments in Daling River is 0.6cm/a in the past 3000 years,of which the sedimentation rate is 0.8cm/a in the past 2000a?1000a,and 0.53cm/a in the past 1000-500a,and the maximum deposition rate has reached lcm/a in the past 1000 years.The sedimentation rate of Late Holocene is higher than that of Pre-Middle Holocene.3.Through the use of two different climatic proxy indicators,clay minerals and macro-element geochemistry,the vertical changes and environmental significance of the Holocene indicators in hole NQ-1 were comprehensively analyzed.There were two alternations of cold and warm at the end of late Pleistocene,and the climate became warmer in the early and middle Holocene.During the period of 2500?1000 years ago,there were roughly 6 climate changes with alternating cold and warm.4.The ratio of Fe/Mn and the crystallinity of illite have a good indication of climate change in the Daling River area,while the ratio of(illite+chlorite)/(montmorillonite+kaolinite)has a weak impact on the environment in this region,and the relative content of montmorillonite and the ratio of kaolinite/montmorillonite have a lagging response to climate change.