Study on Characteristics and Its Stratigraphic Classification and Correlation of Ordovician in Shunan area of Sichuan Basin

By analysis and study of bulk of wells and outcropping,on the base of generalized various structures and stratigraphic classifications of Ordovician of different periods in Shunan and adjacent areas of Sichuan Basin,in terms of lithostratigraphy characteristics and comprehensive analysis of its Paleontologic characteristics and rock resistivity,the Ordovician in south Sichuan basin could be divided into six formations:Tongzi,Honghuayuan and Meitan Formation of Lower Ordovician,Shizipu and Baota Formation of Middle Ordovician and Wufeng Formation of Upper Ordovician.Study on the stratigraphic characteristics and distribution indicates that Lower Ordovician mainly develops clastic rock and clip carbonate rock.Middle Ordovician develops marine carbonate.Lower part of Upper Ordovician develops marine carbonate and it's upper part develops clastic.The thickness of each Formation of Ordovician in the studied area gradually reduces from southeast to northwest.