Development of the Ediacaran(Sinian) multicellular organisms and formation of the source rocks in the Yangtze area

The productivity of organisms and abundances of preserved organic matter are believed to be important conditions for the formation of source rocks.The multicellular organisms appeared in substantial amounts in the Yangtze shallow sea during the Doushantuoan(Ediacaran).The black mudstones(shales) were once deposited as the water-rich gruel sediments during the Doushantuoan.At that time,the oxidation-reduction interfaces were relatively shallower.The organic remains could be rapidly covered by the gruel sediments so as to form the source rocks.The Doushantuoan(Ediacaran) went through sharp changes in chemical,climatic and environmental aspects,and thus may be a key period for the life evolution,development of organic productivity and formation of the source rocks in the Yangtze area.