Geological Attributes and Formation Mechanism of T11 Boundary in Songliao Basin

Based on interpretation and analysis of seismic and well drilling data in Songliao Basin,the characteristics of T11 and the bottom boundary of Yaojia Formation are elaborately described and studied.The four fold belts(large-scale,broad,low-relief,north-east-north-trending) and thrust systems are distinguished through the analysis.It is indicated through these characteristics that the regional angular unconformity T11 was formed in a compressional regime during the post-rift thermal subsidence of Songliao Basin.T11 boundary was formed during the period of late Cretaceous(about 88.5Ma).This is in consistence with the time of a great reorganization of plate tectonic in the Mesozoic time.It is therefore argued that the T11 bottom boundary of Yaojia Formation in Songliao Basin is the responding surface to interaction between Pacific plate and Eurasian plate in late Mesozoic.