Characteristics of Biomarker Compounds and Its Implication of Middle Jurassic Oil Shale Seguence in Shuanghu Area,Northern Tibet Plateau

LIN Jin hui; YI Hai sheng; LI Yong; WANG Cheng shan; PENG Ping an

Abundant hiomarkcrs, including n-alkancs, isoprcnoid, stcrancs and tcrpancs, have been detected by GC-MS from the middle Jurassic oil shalcs in the Shuanghu area northern Tibet plateau.N-alkancs contain carbon number nC₁₂-nC₃₅ with a rclativclv wide range,nC₁₅,nC₁₆ or nC₁₇ as the highest peak.Examination of the relative abundance show a dominancc of low carbon molecular components in the n-alkanc.Pr/Ph ratio in oil shalcs range from 0.77 to 1.59, and it fluetuatcs in the vertical section.The upper and lower part of the oil shalcs have slight predominance of pristanc, whereas phytune dominates in the middle part of the oil shale sequence.C₃₀-hopanc is the most abundant in the hopanc series.According to the rclativclv abundance, pcntacvclic tritcrpanc>tricvclic tcrpanc>quartcvclic tcrpanc.Stcranc ∑C₂₇/C₂₉ ratio ranges from 0.79 to 1.20} and ∑(C₂₇+C₂₈)>∑C₂₉.The carbon number distribution of the stcrancs show a slight predominance of C₂₇ components over C₂₉ in the lower part of the oil shalcs and a slight dominance of C₂₉ component over C₂₇ in the upper part of the oil shalcs sequence.C₂₇-diastcranc/ C₂₇-stcranc ratio range from 0.51 to 3.63,which also fluctuate in the vertical section.It indicates organic matter of algacl origin with proper ratio contribution from terrestrial sources.The organic matter in the oil shalcs is mature.Different Pr/Ph and C₂₇-diastcrancs/C₂₇-stcrancs proved cspcciallv useful in asscssing variation in dcpositional environment and recognizing preservation potential of the organic matter.

1 Testing and Analyzing Centre, Chengdu University of Technology, Chengdu 610059;

2 Institute of Sedimentology, Chengdu University of Technology,Chengdu 610059

Received Date: 2000-05-09

Key words:

Abstract: Abundant hiomarkcrs, including n-alkancs, isoprcnoid, stcrancs and tcrpancs, have been detected by GC-MS from the middle Jurassic oil shalcs in the Shuanghu area northern Tibet plateau.N-alkancs contain carbon number nC₁₂-nC₃₅ with a rclativclv wide range,nC₁₅,nC₁₆ or nC₁₇ as the highest peak.Examination of the relative abundance show a dominancc of low carbon molecular components in the n-alkanc.Pr/Ph ratio in oil shalcs range from 0.77 to 1.59, and it fluetuatcs in the vertical section.The upper and lower part of the oil shalcs have slight predominance of pristanc, whereas phytune dominates in the middle part of the oil shale sequence.C₃₀-hopanc is the most abundant in the hopanc series.According to the rclativclv abundance, pcntacvclic tritcrpanc>tricvclic tcrpanc>quartcvclic tcrpanc.Stcranc ∑C₂₇/C₂₉ ratio ranges from 0.79 to 1.20} and ∑(C₂₇+C₂₈)>∑C₂₉.The carbon number distribution of the stcrancs show a slight predominance of C₂₇ components over C₂₉ in the lower part of the oil shalcs and a slight dominance of C₂₉ component over C₂₇ in the upper part of the oil shalcs sequence.C₂₇-diastcranc/ C₂₇-stcranc ratio range from 0.51 to 3.63,which also fluctuate in the vertical section.It indicates organic matter of algacl origin with proper ratio contribution from terrestrial sources.The organic matter in the oil shalcs is mature.Different Pr/Ph and C₂₇-diastcrancs/C₂₇-stcrancs proved cspcciallv useful in asscssing variation in dcpositional environment and recognizing preservation potential of the organic matter.

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Characteristics of Biomarker Compounds and Its Implication of Middle Jurassic Oil Shale Seguence in Shuanghu Area,Northern Tibet Plateau

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