Role of carbonaceous matter for redox systems in sediments and its geoscientific significance for diagenesis

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The purpose of this study is to elucidate the role of carbonaceous matter for oxidation-reduction potential (redox) of pore water in sediments for initial deposition and lithification.Water chemistry such as redox, pH and electrical conductivity of pore water in sediments was measured in the selected fields of peat swamps, flood planes, delta surfaces, coral reefs, limestone caves and hot springs associated with manganese oxide. The organic and inorganic carbon in each host sediment was determined by using transmitted and reflected light, X-ray diffractometer, CN corder and CHN analyzer.Redox ranges of 10 to l2mV were obtained for samples from peat swamp environments, 120 to 210mV for flood plane and delta, 97 to 118mV for coral reef, 290 to 334mV for limestone cave and 150 to 314mV for hot spring environments. Total carbon content ranges up to 86wt% for peat sediments, up to 10wt% for flood plane and delta sediments, up to 10wt% for coral reef sediments, up to 45wt% for limestone cave sediments, and 0.0wt% for hot spring sediments were recorded. It is generally observed that carbonaceous matter strongly affects redox systems of sediments except for samples fromlimestone caves. The content of organic carbon in some sedimentary environments appears to be inversely proportional to that of inorganic carbon, which suggests transformation of organic carbon to inorganic carbon.A relationship between redox and carbon content from selected sedimentary environments has been identified in this study and the effect of duration for geochemical reactions on the basis of geochronological or paleontological evidence requires further detailed study.