High temperature and high pressure hydrous pyrolysis experiments were conducted on type Ⅲ source rocks from Well Tao 10 in Liaohe Basin under various conditions to investigate the role of biomarker maturity parameters at different thermal evolution stages.The expelled oils collected from these experiments were separated into saturated hydrocarbons

aromatic hydrocarbons

non-hydrocarbons and asphaltene

and the saturated fractions were analyzed by GC/MS.Taking the simulation temperature as the scales of maturity

the biomarkers that are indicative of thermal maturity evolution were detected from n-alkane

isoprenoid alkane

tricyclic terpane

tetracyclic terpane

hopane and sterane

and their parameter index were also calculated.Based on the different sensitivities of different biomarkers to thermal action

the ratio of different biomarkers may reflect different thermal stages.With the simulation temperature increasing

the hopanes may be turned into tricyclic terpanes

Tm may be turned into Ts

and the configurations of isomers will be transformed from 22R to 22S

thus the ∑tricyclic terpane/∑hopane

Ts/Tm and C

31

-hopanes 22S/(22S+22R) may be good indicators of thermal stages.But in the stage of maturity to over-maturity

the C

24

-tetracyclic terpane/∑hopanes

C

30

βα-moretane / C

30

αβ-hopane and C

29

-sterane ββ/(αα+ββ) are more suitable indicators.Therefore

samples at different thermal evolution stages have their own optimal biomarker assemblages providing a theoretical basis for determining thermal evolution stage of source rocks by using maturity parameters in the study area.