Based on statistical analysis of vitrinite reflectance (Ro) data of 23 mudstone samples from five wells in Hefei basin

the thermal evolution characteristics of the basin during Mesozoic and Cenozoic are comprehensively studied by sieve correlating the slope of vitrinite reflectance vs. depth profile (Ro H ) and the corresponding geothermal gradients. TheRo values of the Permian

Lower Jurassic and Lower Cretaceous in different blocks of the basin vary significantly and range from 0.82% to 2.70%

while the slopes of the correspondingRo H profiles are remarkably larger than that of the Upper Cretaceous and Lower Tertiary

indicating an obvious hiatus between the Lower and Upper Cretaceous. The geothermal gradient in the Lower Cretaceous ranges between 70.80℃/km and 130.90℃/km

and that in relatively stable area is near 70.80℃/km

which indicate that there have been a relatively large regional tectonic thermal event during the Early Cretaceous. TheRo of the Upper Cretaceous and Lower Tertiary distribute narrowly between 0.40% and 0.74% and the geothermal gradient is 38.30℃/km. The basin has been uplifted

as a whole

and cooled down since Late Tertiary

lowering the geothermal gradient to the current 27.50℃/km.