Abstract: The 3rd member of Yingcheng Formation was detailed studied by large scale mapping of lithology and lithofacies, 2D surveying of small lithology and lithofacies section and identifying rocks.The 3rd member of Yingcheng Formation contains 2 cycles which changed from intermediate-basic rocks to intermediate-acidic rocks: Cycle①changed upward from quartz-andesite, andesite, andesitic agglomeratic lava, andesitic agglomerate, andesitic breccia and andesitic breccia tuff, to sandy tuff, dacitic tuff lava. Cycle ② changed from basaltic andesite, basaltic agglomeratic lava to dacite, dacitic tuff lava, dacitic tuff. The upward vertical lithofacies succession of cycle ①is: lower subfacies of effusive facies, diatreme subfacies of volcanic conduit facies, airfall subfacies of explosive facies , reworked volcanogenic sediments sub-facies of volcanogenic sedimentary facies , pyroclastic flow subfacies of explosive face. The upward vertical lithofacies succession for cycle ②is: lower and upper subfacies of effusive facies, diatreme subfacies of volcanic conduit facies, lower subfacies of effusive facies, inner sufacies of intrusive facies, lower subfacies of effusive facies, pyroclastic flow subfacies of explosive facies, reworked volcanogenic sediment subfacies of volcanogenic sediment facies, lower subfacies of effusive facies. The lava in 3rd part of Yingcheng Formation erupted in the late period of fault subsidence and it is the important lithology record of the Songliao Basin’s transform from a fault subsidence basin to a sag basin.

Key words: Songliao Basin, Yingcheng Formation, volcanic rocks, lithological and lithofacies succession