PROGRESSIVE TRANSFORMATION——THE THIBD MODE OF CLOSURE OF GEOSYNCLINES

The author hold that the mode of closure of the Variscan geosyncline in northern Jilin is neither sudden transformation nor gradual transformation but progressive transformation.The Jilin-Heilongjiang fold system is composed of the Caledonian, Early variscan and Early Indosinian tectonic layers, covered by the platform-type sedimentary cover, formed in the stage of rejuvenation of the peripacific continental margins （unconformably again）, which is just the manifestation of the third mode of closure of geosynclines. This paper briefly describes its basic characteristics.