Optically Stimulated Luminescence Chronology Ofhole EGQD14 In Yangtze River Delta And The Paleoenvironment Change

As a cradle of act as a important“bridge”which ties among lithosphere,biosphere and hydrosphere.China is backed by the world's largest Eurasian continent and faces the largest ocean.The huge difference in the nature of land and sea determines the particularity of China's climate evolution and the advantage of paleoclimate research.The history of material,energy and information exchanged between continents and oceans has been faithfully recorded in the land-sea interaction strata and their evolution process in the delta region formed by rivers flowing into the sea in China.The Yangtze river delta is the largest delta in China,and the strata have preserved a large amount of information about the ancient environment and human activities.Optically stimulated luminescence?OSL?was studied by means of a long drill hole in the lower chegu river valley of the Yangtze river delta in this paper.In terms of paleoclimate evolution,the quaternary stratigraphic time frame since late pleistocene in the Yangtze delta was established to invert the paleoclimate change process.For the dating of quaternary strata in the Yangtze river delta,geologists usually use the ¹⁴C method in the past.However,due to the high deposition rate in the delta area and the strong transformation of rivers and oceans,it is often difficult to find dating materials,and the dating results are not ideal due to the carbon pool effect.After years of development,photoluminescence dating method has been widely used in quaternary sediments with accuracy and precision up to 100 years.In this paper,14 coarse quartz samples in the hole of EGQD14 were collected for photoluminescence dating based on single slice regenerative dose method?SAR?.The acceptability of the results is verified from two aspects of internal principle control and external method constraint.In the end,the"bad films"with large errors are eliminated to form reliable dating results.This thesis argues that:1.The sediment type of drilling hole EGQD14 is dominated by fine-grained silty clay and clayey silty sand.Based on the characteristics of core sedimentary facies and biological evidence as well as the analysis of shallow strata data in the Yangtze river delta,the sedimentary layer recorded the sedimentary environment changes since the late Pleistocene.2.The photoluminescence age was found to be reliable by selecting appropriate preheating temperature and examining feldspar pollution,sensible change,heat transfer effect and residual dose.3.The age of photoluminescence was consistent with the change of depth.4.Before the last deglaciation?¹1.8 ka?,the sea level was lower and the delta was only a transport channel.During the great warm period of middle holocene,the sea level dropped from high sea level and the delta began to form.In the late holocene?2.0-0 ka?,the deposition rate reached a peak,and the sea-pushing rate of the delta accelerated.In this period,human activities became the main external driving force for shoreline propulsion.