Filling Characteristics And Evolution Of Mesozoic In Liuhe Basin

Liuhe basin belongs to the eastern basin group in the Northeast China.The basin is located on the east side of the Dun-Mi fault zone and controlled by two NE faults,it is a NE-trending narrow basin.The Mesozoic strata comprise Middle Jurassic Houjiatun Formation,Lower Cretaceous Guosong Formation,Yingzuilazi Formation,Linzitou Formation,Xiahuadianzi Formation and Hengtongshan Formation.Combining core description,seismic interpretation,and indoor comprehensive analysis,the sedimentary facies is identified,the filling sequence is divided,the Mesozoic tectonic evolution of the basin is discussed.After the exact and careful research,this paper comes to the following conclusions:1.Types of rock and sedimentary faciesThe rock types in Liuhe basin are divided into 4 classes and 11 subclasses.Clastic rocks include conglomerate,sandstone,siltstone and mudstone,and pyroclastic sedimentary rocks include tuff conglomerate,tuff sandstone,tuff siltstone and tuff mudstone,and pyroclastic rocks include tuff,lava and intrusive rocks.The sedimentary facies include fan delta facies,lacustrine facies and hybrid facies.2.Filling sequence and filling typesBased on lithologic changes and facies assemblages,the Lower Cretaceous strata is divided into 14 third-order sequences,and there are 8 filling types.There are 5 clastic rocks filling types,i.e.,positive-reverse cycle,reverse-positive cycle,reverse cycle,positive cycle and positive-reverse cycle interaction.There are 3 hybrid filling types,i.e.,lowstand systems tract volcanic rock,transgressive – highstand systems tract volcanic rock and highstand systems tract volcanic rocks.3.Basin evolutionBy structural and stratigraphic analysis,the structure framework of Mesozoic in Liuhe basin was established.Liuhe basin is a strike-slip double-fault graben basin,controlled by the left-lateral strike-slip movement of the Dun-Mi fault in the Early Cretaceous,and the tectonic setting is the NW subduction of the paleo-Pacific plate to the Eurasian plate.Liuhe basin underwent six stage in Mesozoic,including initial subsidence stage in Middle Jurassic,uplift denudation stage in Late Jurassic and four volcanic eruptions-subsidence stage in Early Cretaceous.