The Geochemical Cycle Analysis For The Yaojia Formation-the Member 1 Of Nenjiang Formation Deposited In The Late Cretaceous From The Songliao Basin

Since the beginning of the 21 st century,the effect of greenhouse has become a worldwide problem facing humanity.The rapid rise of carbon dioxide concentration,the melting of bipolar glaciers,rising sea levels,and rising global temperatures are all challenges in the new century.The Cretaceous period is a typical greenhouse period,and there are no ice on both poles.Therefore,it is important to study the paleoclimate and paleoenvironment of the Cretaceous period and master the law of climate change.The Songliao Basin preserves the most complete strata of the Cretaceous continental facies.The Continental Scientific Drilling Project of the Songliao Basin aims to penetrate the Cretaceous basin and obtain a continuous and complete core,providing a high-resolution continental stratigraphic sedimentary record.This material selects the core of the Yaojia Formation(1128.17m-1285.91m)and the Member 1 of Nenjiang Formation(1025.13m-1128.17m)of the Late Cretaceous,and XRF scans the core to obtain the elemental content data of the core.Through the geochemical method Chome-Fischer treatment,the element stacking pattern of Yaojia formation and Member 1 of Nenjiang Formation was obtained;the lake level change of Yaojia formation and Member 1 of Nenjiang Formation was reconstructed by natural gamma(GR)curve.According to the significance of the element index and the lake plane obtained by the GR curve,the paleoenvironment and paleoclimate are analyzed.Through the analysis of the Yaojia Formation and Member 1 of Nenjiang Formation,it is initially obtained: The Yaojia Formation is mainly a change trend of water intake-water retreat-water intake.At the beginning of the deposition of Yao section,the cliate was humid and the rainfall increased.The surface runoff in the basin basin increased,the rivers were strong,the input of land-based materials increased,and the lake level rose.Then the lake level is lowered,the salinity is increased,the climate is changed from moist to semi-wet,and the oxidizing property is enhanced.The sediments are mainly gray-brown gray-red mudstone(Cretaceous red layer).Finally,the input of terrigenous clastic material increased,the hydrodynamic force was strong,and the lake level increased.The Member 1 of Nenjiang Formation is mainly a deep lake-semi-deep lake-deep lake transformation process.The lake level at the bottom of the Member 1 of Nenjiang Formation has been in a high water level.The lake water has expanded to the entire basin.The terrigenous debris,salinity and weathering indicators have not changed much.The paleoclimate is relatively stable.Then the lake level began to decline,the salinity increased,the weathering index decreased,and the lake changed from the deep lake to the semi-deep lake.In addition,the obtained Chemo-Fischer curve is subjected to CEEMD analysis,and the obtained result is subjected to spectrum analysis to obtain astronomical period in which the control element is stacked.In most elements and elements ratio,the signal of the Milankovic signal Eccentricity(E),Slope(O)and Precession(P)is recognized.The control factors of the astronomical cycle of the Yaojia Formation to the Nenjiang Formation have changed.The Yaojia Formation is mainly affected by the 1.2Ma long slope period,while the Member 1 of Nenjiang Formation can mainly find the 405 Ka long eccentricity period and the 124 Ka eccentricity period control.It shows that from the Yaojia formation to the Member 1 of Nenjiang Formation,the main controlling factors of the astronomical orbit changed from slope to eccentricity.