Considerations in Epimerization of Sterane and Triterpane as Indicators of Thermal History of Sedimentrary Rocks

概要

論文の詳細を見る
24 mudstone samples from Shinjo Oil Field and Nishiyama Oil Field (Neogene Tertiary, Japan) were examined by gas chromatography-mass spectrometry to investigate the extent of configurational isomerization (epimerization) of the so-called biological marker compounds (steranes and triterpanes).The increases of the ratios of 20S/20R-24-ethyl-5α(H), 14α(H), 17α(H)-cholestane and of 22S/22R-17α(H), 21β(H)-bishomohopane (C32) with maturation were recognized clearly. However, it was also recognized that the rate of epimerization of sterane was relatively higher than of triterpane in two sedimentary Basin in Japan in comparison with Paris Basin (France), Uinta Basin (U. S. A.) and Bohai Bay Basin (China). It was considered that the effect of the difference of heating rate among the sedimentary Basins appeared. That is, higher rates of epimerization of sterane than of triterpane in Japanese two Basins are possiblly due to relatively higher heating rates which are attributable to high geothermal gradients and high rates of burial.In addition, the evaluation of the level of maturation by the equivalent reaction temperature and equivalent reaction time, which would be determined by the two kinetic parameters such as the extent of epimerization of sterane and triterpane, was proposed based on the kinetic considerations in this paper.
日本堆積学会の論文