Keywords: 
• Upper-Sinian /
• Dengying formation /
• cyanobacteria dolostone /
• hydrocarbon source

Abstract: Dengying formations 2 and 3 members of upper-Sinian is one of major nature gas reservior in Sichuang basin. In light colour dolostone abound with carbonification blackly non-stromatolite ecologic system cyanobacteria dolostone. It's developed not also in depositional and cementational stage,but also in hypergene diagenetic stage.At the depositional stage, it occure in laminae or surounded the grain growth in all sides.The singel bed thickness of these cyanobacteria dolostones from 1 mm to over 10 cm. And total thickness occupy about 10 percent in 2 and 3 members of Denging formation. Sometimes it show up incontinual small blackly points developed in whitely stromatolite ecologic system cyanobacteria dolostones,suck as stromatalolates, oncolite and others.At the hypergene diagenetic stage,the blackly non-stromatolite ecologic system cyanobactria mainly occurred in many generations linely laminae interbeded with wihite coloure fiber texture dolostone laminae filling the karstic cavity and channel, even in enlargeie dissolived crack.The major sharps of non-stromatolite ecalogic system cyanobactria are sphere,ellipsod and cudgel,occasionally are mushroom,monkhat and others.The colongs presented sharp are string bead,grass cluster,croteh and like the valcanic eruption,etc. All of these sharps show palaeocology of upword groweh or toword the centre of karstic cavity and channel. Degradation in test of modern cyanobactria evidenced that non-stromatolite ecologic system cyanobacteria dolostones is one of hydrocarbon source rock in Dengying formation.