Late Cretaceous To Early Paleocene Paleoclimate Change Of Datang Section In Nanxiong Basin

Global climate change has become the focus of human attention and research.Throughout the geological history of climate change,the Cretaceous paleotemperature is much higher than today.The Cretaceous-Paleogene period is the hottest and most typical greenhouse climate period since the Phanerozoic.Deeply exploring the climate change during this period is one of great significance for predicting future climate change and solving the current carbon dioxide concentration.The degree of greenhouse effect has increased dramatically,which is an important part of greenhouse effect.However,up to now,the study of continuous paleoclimate records in the Cretaceous-Paleogene period is still very scarce.Although some scholars have reconstructed the paleotemperature of this period through continental sedimentary materials,the high fraction and continuous climate records are limited to marine records,and the reconstructed continental paleoclimate records are still few,so it is impossible to make effective sea-land comparison.Therefore,it is particularly important to obtain continuous continental paleoclimate records for land-sea correlation.The Datang section of Nanxiong Basin is a set of Late Cretaceous-Early Paleocene strata dominated by red clastic rocks.The strata are loose in structure,continuous in sedimentation,rich in paleontological fossils and well exposed.It is a good material for studying paleoclimate change from Late Cretaceous to Early Paleocene.Therefore,many scholars have carried out a series of studies here,making it a non-marine Cretaceous.The criteria for stratigraphic division and correlation of the Cretaceous-Paleogene strata,paleontology,dinosaur extinction and K/T boundary are also the most delicate hot spots in China.Based on the work of predecessors,through systematic experimental tests of rock magnetism,element geochemistry and diffuse reflectance spectroscopy,this paper compares magnetic susceptibility,CIA with deep-sea oxygen isotope,soil-forming carbonate oxygen isotope,global sea level change and sea surface temperature data,and analyses the mechanism of magnetic susceptibility change in profile and its paleoclimatic significance,and compares it with South China in the same period.Comparing with other paleoclimate records in Nanxiong basin,we will discussed the higher resolution magnetic susceptibility change and paleoclimate evolution process.This paper draws the following conclusions:(1)The strata of Nanxiong Basin are mainly red,the sediments are mainly fine silt and fine sand,and there are also coarse gravel beds.But regardless of the size of the particle,the color is red.The depth of red varies,and the depth of red varies with bedding/stratification.Therefore,the red color of the stratum is formed at the same time as the bedding/stratification,which is the primary color.Hematite is the only magnetic-carrying mineral that can be detected.It reflects the geological environment of long-term high temperature oxidation and is formed during the oxidation process of long-term soil formation on the surface.Its high temperature oxidation environment is much hotter and less rainy than when the fifth layer of Paleosol was formed in the Quaternary on the Loess Plateau.(2)The magnetic susceptibility is consistent with the deep-sea oxygen isotope variation,so the change of magnetic susceptibility in Nanxiong Basin may record the global climate change,and the enhancement mechanism of magnetic susceptibility can still be explained by the "theory of soil formation";(3)Combining with magnetic susceptibility and elemental geochemical characteristics,the oxygen isotopes of carbonate in Nanxiong Basin and the crystallinity of illite in Nanxiong Basin are compared./ Weathering index and global sea level and sea surface temperature data show that the evolution of paleoclimate in Nanxiong Basin during 72-61.5 Ma is synchronized with global climate change,which can be divided into three stages: 1)The first stage is 72-71.5 Ma,when the climate is mainly hot and humid,there is a rapid change of climate around 71.5 Ma,and then gradually warming up after 71.5 Ma;2)The second stage is 71.5-66 Ma,during which the climate is generally warm and dry,and there is an obvious cooling event at about 70.7Ma,which may be related to the global record of 70.5 Ma climate cooling event,then the temperature rises after 70 Ma,because the samples in this section are incomplete,it can not be further compared;there is also a rapid cooling of climate at 66.75-66.25 Ma,until66 Ma gas.The location of K/T boundary is the same as that of other records,which may record the late Maastricht Warming Event(LME);3)The third stage is 66-61.5 Ma,which is mainly humid and hot,and there were many climate fluctuations.The climate of66-64.7 Ma gradually changed from warm-dry to humid-hot,except for 65.8-65.9 Ma,which had a short-term cooling,and also experienced two climate cooling periods.~ 62.6Ma,the climate is mainly hot and humid,and there were three significant cooling events during the period of 62.6-61.5 Ma,the temperature gradually increased,the climate was still relatively hot and humid,indicating that the paleoclimate was not unchanged from the Late Cretaceous to the Early Paleocene,and its climate change also has many cycles of cold and warm alternation.