Application Of Elements Analysis To The Study Of Paleosedimentary Environments In The Liujiang Basin

In the Liujiang basin,the stratigraphy is well developed and records various important geological events and geological phenomena such as crustal movement,magmatic activity,sedimentary environment,climate evolution and biological evolution and development from the Tertiary to the Cenozoic,which provides relatively comprehensive basic geological information for studying the evolution of palaeoenvironment in different stages of geological history.Elemental analysis method is one of the important tools for palaeoenvironmental recovery,but there are many indicators in the current analysis method,and there are large differences in the criteria classified by various scholars,which make the analysis results have certain deviations,so it is important to explore the role of elements in the palaeoenvironmental analysis method and establish a perfect indicator system.Through the analysis of water samples and water sediments in different modern environments,and the analysis of weathering of rocks,migration and enrichment of elements and geochemical behavior of elements in different environments,the facies elements of water salinity,climate and redox environment were selected.A database of ancient sedimentary environments was established by collecting raw data from geochemical analyses of mudstones in different regions,and a palaeoenvironmental logistic regression evaluation model was established using cluster analysis and logistic regression with the selected facies elements as "influence factors".The training results of the model shows that the prediction accuracy is more than 90%,which verified the reliability of the model.The model is tested by using the test samples and the sample data of modern sedimentation system,and the judgment results match with the actual results above 80%,which shows that the model has good effect and can be used to distinguish the palaeoenvironment.Through intensive sampling of strata from different eras in the Liujiang basin and whole-element determination,the characteristics of elemental abundance changes in the longitudinal direction were analyzed,and the palaeoenvironment was recovered by using the palaeoenvironmental logistic regression judgment model.During the Upper Paleozoic period,the Jingeryu Formation of the Qingbaikou System,the study area was in an arid and hot climate with a shallow coastal marine environment.The climate was hot and arid during the Early Paleozoic Mantou and Maozhuang Formations,and increased in humidity during the Xuzhuang Formation,turning into a warm and humid climate,with an obvious sea retreat in the Late Cambrian,and a warm and humid coastal oxidation environment during the Kushan Formation.In the early Ordovician Yeli Formation,the sea advance expanded again and the climate remained warm and humid.From the late Early Paleozoic to the early Late Paleozoic,the basin was in the period of denudation.After the Late Carboniferous,the Central Dynasty platform began to slowly subsidence,the sedimentary datum slowly rose,and became the intersection of land and sea.At the end of the Late Carboniferous,the area was slowly uplifted and the seawater retreated,and the area was completely separated from the marine environment in the Early Permian.By the Late Permian period,the climate became relatively arid.In the late Triassic,the climate became warm and wet again in the Heishangyao Formation.With the intensification of the Indochina movement,the Lower Jurassic Xiahuayuan Formation was in a humid temperate climate.