Organic Matter Source And Paleoclimate Significance In Ningjinbo Area Of Xingtai City,Hebei Province Since Late Pleistocene

The Ningjinbo Area of Xingtai City is in a key position in the Hebei Plain,with the Taihang Mountains in the west and the plain area in the east.It is a typical area with paleoclimatic changes.The lake sediments in the Ningjinbo area are extensively developed,and the lake strata are large and continuous.Better sedimentary characteristics are the key to revealing the Quaternary climate.At the same time,as the research focus of lacustrine sediments,the study of the source of organic matter in sediments is of great significance.The source of organic matter can be used to infer the input problems of lakes in different periods and then to infer the paleoclimate environment in that period.In this paper,the organic carbon isotope(?₁₃C_org),carbonto-nitrogen ratio?C/N?,and total organic carbon?TOC?in lacustrine sediments are combined with chromatic significance analysis to analyze the organic matter source and lake productivity in Ningjinbo Area.The preservation status of the lake reflects the ecological environment of the lake area and the sedimentary environment of the sediment,and finally analyzes the evolution of the paleoclimate since the late Pleistocene.Through the measurement and analysis of the organic carbon isotope(?₁₃C_org),carbon-to-nitrogen ratio?C/N?,total organic carbon?TOC?,and chromaticity?L *,a *,b *?of the depositional profile,the following are discussed and obtained understanding:?1?The organic carbon isotope(?₁₃C_org)value in the sediments of Ningjinbo area is generally negative.It is speculated that organic matter originates from terrestrial higher plants,and the carbon to nitrogen ratio?C/N?value is between 2.5 and 13,The total organic carbon?TOC?value is relatively small.It is speculated that the early sedimentation process will slightly affect the C/N value.The source of organic matter in its sediment is divided into six stages according to the stratum from old to new: ? ?terrestrial higher plants as the main body,? Decreased organic matter content is mainly imported from terrestrial C3 plants,? increased organic matter content and algae plants,? decreased organic matter content is mainly imported from terrestrial C3 plants,? increased organic matter content,a slight increase in aquatic plants and C4 plants,?input of various and diverse sources of organic matter Happening.?2?According to the sources of organic matter and chromaticity index,the climate from the late Pleistocene to 73 ka is generally cold and dry,interspersed with warm and humid periods.The climate is: ? warm and humid,? cold and dry,? warm and humid,? cold and dry,? climate is warm-cold-warm Mild drought,? warm and humid.The lake area increased during the warm and humid period;the lake area contracted and the water depth became shallow during the cold and dry period.?3?Through comparison with solar radiation,ice volume,and stalagmite oxygen isotopes,the correlation between the climate of Ningjinbo area and solar radiation and the East Asian monsoon was discovered.Ningjinbo area exhibited an ice age under the influence of solar radiation on the ten thousand years scale-Cycles in the interglacial period are affected by the East Asian monsoon on a short-term scale,making the cold period cold,dry and less rainy;the warm period warmer,humid and rainier.