Steranes in sedimentary rocks and petroleums are believed to be largely deribed from the biologically abundant sterols, such as cholesterol and sitosterol. Sterols in recent sediments and biological sources have been well studied, and it has been known that sterol composition in sediment is relatable to ecological system of the sedimentary environment. If sterane composition in the sedimentary rock is a relic of former sterol composition, we cah estimate the paleoenvironment of the sedimentary rock based on the sterane composition.
In this article, distribution patterns of selected steranes (5α-C_27, C_28, C_29 steranes) in 44 marine and non-marine mudstones (from Quaternary to Cretaceous) in Japan were investigated by GC-MS (gas chromatography and mass spectrometry) method for possible application in paleoenvironmental analysis of sedimentary rocks. Consequently, it becomes clear that there is a close relation between 5α-sterane composition and paleoenvironment, and that is generally consistent with the relation between sterol compositions in recent sediments and their present environments with some exceptions of non-marine mudstones. It is concluded that sedimentary 5α-steranes are the possible indicators to estimate the paleoenvironment of sedimentary rock.