Organic maturity indexes, statistical thermal alteration index (stTAI) and vitrinite reflectance (Ro) were applied to geological phenomena, namely diagenesis, unconformity, faulting and contact metamorphism. As diagenesis of sedimentary rocks progresses, generally stTAI decreases but Ro increases. The effects of unconformity and faulting appear in stTAI more than in Ro. The values of Ro regularly increase with decreasing distance from the igneous dyke, but those of stTAI have no decreasing trend. It is concluded from these measurements that stTAI is more sensitive to heating time and Ro is more sensitive to heating temperature. The studies by means of these organic maturity indexes combined with inorganic mineral indexes might be able to clarify various geological phenomena.

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C₁₄ to C₂₈ n-alkan-1-ols, together with C₁₄-C₃₁ n-alkan-2-ols, C₁₄-C₂₉ n-alkan-3-ols, C₂₀-C₂₉ n-alkan-4-ols, C₁₄-C₂₇ n-alkan-5-ols and C₁₄-C₂₄ n-alkan-6-ols were identified in Neogene sediments from Shinjo basin, Yamagata Prefecture, Japan. Total amounts of n-alkan-1-ols tended to decrease from 50μg/gC in the uppermost section to 13μg/gC in the lower sections, whereas those of 2-ols and 3-ols slightly increased in the middle and then decreased in the lower sections. On the contrary, n-alkan-4-ols, n-alkan-5-ols and n-alkan-6-ols were absent or negligibly small in the upper sections and detectable only in the middle to lower sections. Primary alkanols, n-alkan-1-ols, had a peak maximum at C₁₆ or C₁₈ and showed a small but evident even carbon-number preference particularly in the range of C₁₄-C₂₀. On the other hand, secondary alkanols, exemplified by n-alkan-2-ols had no significant even-odd preference and the peak maximum, being at C₁₃-C₁₅ in the upper sections appeared to shift gradually to longer chain homologues. Since it is known that the middle to lower sections of this sedimentary sequence correspond to the hydrocarbon expulsion stage, those secondary alkanols are considered to be the intermediate by-products of the isomerization and hydration of alkenes generated by thermal cleavage of long-chain moieties incorporated within kerogen matrix.

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Biomarker compositions in authigenic carbonate crust and surrounding muddy sediment associated with cold-seep communities on the sea floor of Soya Channel off Wakkanai were analysed. These samples were collected from the trawlnet of local fisherman, and were previously well-studied using paleontological methods (Majima et al., 2000). They mentioned shells encased in carbonate crusts as chemosynthesis-based communities.
Both samples contain irregular isoprenoid hydrocarbon, tail to tail linked acyclic C₂₀ isoprenoid 2,6,11,15-tetramethylhexadecane (crocetane), its C₂₅ homologue 2,6,10,15,19-pentamethyleicosane (PME) and several unsaturated derivatives. Their δ¹³C values were depleted between the range of -131.7‰ to -90.9‰PDB. In contrast, the δ¹³C values of n-alkanes were relatively high, ranging from -31.8‰ to -26.2‰. Other specific biomarkers, head to head linked ether-bound acyclic and cyclic biphytanes, were released after HI/LiAlH_4 treatment. Carbon isotopic compositions of these biphytanes were strongly depleted in ¹³C ranging between -127.0‰ to -115.3‰.
The characteristics of biomarkers isolated from carbonate the crust and muddy sediment were quite similar and both showed the existence of methane oxidizing Archaea.
The newly discovered biomarkers in this study, which have a potential for identification of methane oxidizing Archaea, were C₁₃ and C₁₈ isoprenoid ketones. They had also low δ¹³C values ranging from -119.9‰ to -70.6‰.
These results suggest that precipitation of Ca carbonate below sediment-water interface is induced by the anaerobic oxidation of methane (AOM).

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