OGIHARA, Shigenori

Assistant Professor
Geosphere and Biosphere Science Group

Office: Sci.Bldg.No.1-533
TEL: +81-3-5841-4524
FAX: +81-3-5841-4555

Research Field

Organic Geochemistry , minaralogy

Current Research

Biological markers (biomarkers) are complex molecular fossils preserved in the sedimentary environment which are derived from once living organisms. Our efforts in biomarker research are directed towards earth science as well as organic analytical chemistry. The aim of biomarker research is twofold: (1) to establish analytical methods suitable for the determination of the molecular distributions and (2)to explain the significance of the observed distributions within a geological framework. Important information which is obtained from our recent research includes the elucidation of the origin of the organic matter preserved in the source rock, environmental conditions which prevailed during the depositional process, changes which the organic matter experiences as a result of increased burial (a process termed diagenesis), the extent of thermal maturity experienced by a rock, the degree of biodegradation, aspects of source rock mineralogy(lithology) as well as estimation of the age. Furthermore, application of biomarker technology is useful not only in geology but also in the environmental sciences, since anthropogenic activities such as burning of fossil fuels and discharge of sewage into natural water bodies can be monitored as well.
Some of our applications of biomarker research has been involved in the determination of specific molecules suitable for identifying bacteria thriving in hostile environments such as those characterized by highly acidic or alkaline media, unusually highly saline waters, or in high-temperature or high-pressure environments. Biomarkers identified in this work can have important applications as chemical fossils of bacterial activity in extreme environments.
The chemistry of zeolites in sedimentary rocks is another project of my group. Volcanic glass in ashes and vitric tuffs is very suitable for the study of natural zeolites. Specific zeolite reaction series in different types of occurrence cause characteristic zonal distribution of unaltered zone, zeolite zone, and authigenic feldspar zone. The purpose of our research effort is to elucidate the underlying mechanism of phase transitions, such as those occurring in the transformation of volcanic glass to zeolite, and one type of zeolite to another zeolite, by the investigation of their occurrences and analysis of chemical compositions. Rate of zeolitic reaction is another important geological problem which is yet to be fully understood.

Representative Publications

1. Ogihara, S., Composition of clinoptilolite formed from volcanic glass during burial diagenesis, Clays and Clay Minerals, 48, 21-27, 2000.
2. Ogihara, S., Geochemical characteristics of phosphorite and carbonate nodules from Miocene Funakawa Formation, western margin of Yokote Basin, northeast Japan, Sedimentary Geol., 123, 243-256, 1999.
3. Ogihara, S., and R. Ishiwatari, Unusual distribution of hydrocarbons in a hydrothermally-altered phosphorite nodule from Kusu Basin, northern Kyushu, Japan, Org. Geochem., 29, 155-161, 1998.