Molecular Biomarkers Characteristics of Source Rocks from Tanhai Sanma Area in the Huanghua Depression and Its Signification for Sedimentary Facies

Key words: 
• Huanghua depression /
• Sanma area /
• molecular biomarker /
• sedimentary facies /
• sedimentary environment

Abstract: Abundant molecular biomarkers，including nalkanes，isoprenoid，steranes and terpanes，are detected by GCMS in mudstone and sandstone samples from Tanhai Sanma area in the Huanghua Depression. Some typical biomarkers，such as Gammacerane and Oleanane，which can be used to determine the nature of organic matter，are also been founded in samples. The ratio of Pr/Ph is ranging from 0.54 to 3.03，the Ts/Tm is from 1.1 to 9.11，the O/C30H is from 0.005 to 1.48 and the G/C30H is from 0.03 to 1.03，the parameters of molecular biomarkers in Sanma area have distinct difference which reflected the depositional environment under weak oxidation or deoxidize，and are in close relationship with organic matter import and sedimentary environment. Especially，the parameters of biomarkers distributions in mudstone is different at the same section sequence. The results show that the sequence boundary characteristic between turbidite sediment and the mixed was obvious，and it is easy to see that there exists a close link between them. The whole process of the formation is a complete turbidite depositional sequence and a mixed layer that made up of terrestrial origin and algae import formed in the interval of turbidity event.