Analysis Of River Sedimentary Facies In Hetao Plain Of Inner Mongolia And Its Application In Quaternary Geological Survey

The Hetao Plain in the Inner Mongolia is located in the tectonic subsidence area.The river sedimentation is extensive and the sediments are well preserved since the Quaternary.So the Hetao Plain is a good district for studying the sedimentary environment.Due to the flat terrain and the strong influence of human beings,there are deficiencies in the Quaternary geological survey such as suitable theories,methods,processes and innovation expressions.The geologists face the problems of what can we do,how can we do and how to express for the Quaternary geological survey.We extracted the geomorphological information through the remote sensing of the study area.And the characteristics of shallow sediments,sedimentary combination and sedimentary structures were obtained through the shallow drilling(groove drilling and impact drilling).Combining with the age dating data,we determine the different sedimentary subfacies and microfacies.The method of sedimentary facies division is introduced into the Quaternary geological survey in the coved area,which provides theoretical support and innovative expression.After the study above,we got the following conclusions:1?Based on the study of sediment and sedimentary combination from drilling,we determined the fluvial subfacies,embankments subfacies(natural dike microfacies),and flood plain subfacies of rivers in different periods since the Holocene.We set up the river sedimentary model which can guide the Quaternary geological survey in the next period.Through the summary of the sedimentary facies judgment,the criterion of sedimentary facies is put forward which is special to the study area.The criterion can also provide a basis to the geological unit determination.2?We got different results based on the OSL and the 14 C age test about the samples from the drill cores FX1 A and FX2 A.The age for the sediments at the depth of1-2m was 3.920 ± 0.03 ka.The age for the sediments at the depth of 7.14-7.5m was 7.99 ± 0.29 ka.The age for the sediments at the depth of 7.79-7.99 m was10.79 ± 0.73 ka.These results provide an accurate time constraints for determination of the sedimentary facies and the geological survey.3?Through remote sensing interpretation,geological survey route,and shallow drilling,we obtained the 1:50,000 Quaternary geological mapping units combining with the division of sedimentary facies.The geological boundary is determined by the principle of "step by step approximation".We choose the way of “ages + causes + sedimentary facies” as the expression of the mapping unit.The typical borehole histogram is expressed in the corresponding mapping unit.This way can express the geological information accurately and increase the richness of the geological map.The method can be served as a guideline for Quaternary geological survey to the plane area with similar geological conditions.Meanwhile,this method indicated a new direction for different types of basin.