Vitrinite reflectance of the PermoCarboniferous in the north of Songliao Basin is generally high

usually more than 30%

and varies greatly in different tectonic units.The curve of vitrinite reflectance(Ro)depth(H)of the PermoCarboniferous basement in Songliao Basin has two types

which means that they have different thermal history.One is a twosection type.Vitrinite reflectance values change abruptly across the unconformity on top of the PermoCarboniferous.The Ro values and paleotemperature of the PermoCarboniferous strata under the unconformity are obviously higher than that of the overlying strata

indicating that the maximum paleotemperature of PermoCarboniferous strata had been reached before the deposition of the Early Cretaceous Denglouku Formation.The sedimentary strata deposited since the Cretaceous have no influences on the improvement of the PermoCarboniferous paleotemperature and thermal maturity.The other is a pseudolinear type.The Ro values and paleotemperature vary successively across the unconformity on top of the PermoCarboniferous strata

which shows that maximum paleotemperature of the PermoCarboniferous strata had been reached betwen the Late Cretaceous and Oligocene.The sedimentary strata since the Cretaceous contribute to the improvement of PermoCarboniferous paleotemperature and thermal maturity.Based on comprehensive analysis on vitrinite reflectance

fluid inclusion

fissiontrack age and so on

paleotemperature and thermal history of Songliao Basin is restored

and the relation between basin thermal history and hydrocarbon generation is analyzed.