The luminance of fossil pollen (Pinus, Podocarpus, Abies and Picea) from the Neogene sediments in northern Japan, and living pollen (Pinus thunbergii) was measured microscopically by means of computer-aided image processor. The mean value of luminance of indigenous pollen in each rock sample was labeled its "statistical Thermal Alteration Index" (stTAI). The present study identified a relationship between stTAI and vitrinite reflectance (Ro) in sediments.
The difference in stTAI between living pollen and fossilized pollen of 0.30%Ro, the lowest maturity level identified by Ro value, is about 60. This means it may be possible to use stTAI to measure organic maturation in immature sediments under the lowest useful limit of Ro.

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The Yabase field is the largest oil field in Japan. It has produced approximately 34 million barrels of oil. Oil to source-rock correlation and organic-geochemical characterization of the Onnagawa and Funakawa Formations were attempted using triterpanes and steranes in the northern part of the field.
Based on the ratios of C₂₉-norhopane/C₃₀-hopane, C₂₇-diasteranes/C₂₇-steranes, and 20S/(20S+20R) of C₂₉-steranes, produced oils from the Kitaakita and Sotoasahikawa fields can be correlated to the Onnagawa Formation and the lower part of the Funakawa Formation in the Horikawa AK-1 well, and to the lower part of the Onnagawa Formation in the Iiokayama-1 and Tofuiwa-1 wells. The oils from the Nigorikawa and Asahikawa fields can be correlated to the lowermost part of the Onnagawa Formation in the Tofuiwa-1 well.
The westward dilution of biogenic silica with clay minerals is also suggested in the Onnagawa and Funakawa Formations. This characteristic can be attributed to the difference in depositional environment within the Akita basin.

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Organic matter in the oil and the residues after M. A. B. (Methanol-Acetone-Benzene) extraction of source-rocks, which were collected by drilling production tests from various nonmarine depositional layers in Qianan and Nongan area belonging to Jilin oilfield, were analyzed by Curie-point pyrolysis gas chromatography (pyrolysis-GC), elemental analysis, and infrared spectroscopy (IR). Genetic source studies have been performed on the basis of the correlation between the distribution of pyrolysates from kerogen and oils collected in various areas and depositional formations.
The results in this study indicated oil-source rock correlations as follows:
Samples from Nongan area: The n-alkanes distribution patterns in pyrolysates of the oils produced in K₁q⁴ formation were similar to those of the residues from the Jurassic K₁qn¹ source rocks. This fact indicates that K₁q⁴ oils had been generated from the Jurassic source rocks. This result is consistent with the conclusion of previous studies.
Samples from Qianan area: Although previous works concluded that the K₁q⁴ oils have genetic relationship whth K₁qn¹ formation source rocks, the n-alkanes distribution partterns in pyrolysates of K₁q⁴ oil were quite different from those of the residues prepared from K₁qn¹ source rocks. This result suggests that K₁q⁴ is not the source formation of the oils from K₁qn¹ and that another source formation forK₁q⁴ reservoir exists.

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The hydrothermal alteration zone (Murasame Zone), where silicification occurred in the Miocene Bessho and Aoki formations, lies to the northeast of Matsumoto City, central Japan, and has a north-south orientation, a width about 2-3km and a length of 80〜90km. We studied the hydrothermal effects in the Bessho and Aoki formations using vitrinite reflectance. Vitrinite reflectance values become higher close to the Murasame Zone with Ro=3.7% at the maximum. The optical anisotropy of vitrinite macerals suggests that the calibration formula (Barker and Pawlewicz, 1994) could be applied and estimate the maximum paleotemperature of the hydothermal alteration in the Murasame Zone as more than 320℃.

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The Miocene Teradomari Formation is a major source rock in the Niigata oil field. The samples, collected from the type locality of the Teradomari Formation, were classified as (hemi) pelagic mudstone (Ep) or turbidite mudstone (Et) according to their Bouma sequence division. Kerogen maceral composition was identified under a fluorescent microscope. Based on its fluorescent characterization, amorphous kerogen was divided into three types; namely, FA (fluorescent amorphous kerogen), WFA (weakly fluorescent amorphous kerogen) and NFA (non-fluorescent amorphous kerogen). Ep kerogen was mainly composed of WFA, while Et kerogen was mainly of NFA and vitrinite. Relative quantities and chain lengths of aliphatic moieties estimated by FTIR indicate that Ep kerogen has a higher oil generation potential than Et kerogen.

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Lipid compounds were analyzed in three core sediments (16-19cm length) collected in 1993 from the south basin (Core 2), north basin (Core 1) and the northeastern part (Core 3) of Lake Kussharo-ko, Hokkaido Japan. The long-chain (>C23) anteiso compound series (alkanes, fatty acids and alcohols) were detected in every section of every core, which had been known to be unique in the moderately acidiic (pH=3-5) freshwater lake sediments. Abundances of the anteiso compounds varied significantly, showing maxima at the upper and the lower layers of the cores. The vertical variations accorded with variations in the composition of diatom valves remaining in sediments, suggesting a periodical pH fluctuation of the lake water. Only the northeastern core (Core 3) showed a decrease at the uppermost sections (0-2cm), which may probably reflect the recent rapid pH increase during the last decade. The fluctuations were considered to be caused by changes in relative proportion of the inflowing acid hot spring water to the bicarbonate-rich hot spring waters evolving along the lake coast.

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Correlation between vitrinite reflectance (R_o) and T_max from Rock-Eval pyrolysis for Japanese argillaceous rocks is investigated using data of 572 samples from 21 wells drilled on land and offshore Japan. The organic matter of samples is predominantly Type III. Therefore the variation of organic matter type has little influence on the correlation between R_o and T_max The depth variations of the two parameters in each well indicate that the T_max is less reliable than vitrinite reflectance as a maturity parameter. T_max data of cuttings are particularly affected by contamination of drilling mud additives. The correlation between vitrinite reflectance and T_max of Japanese argillaceous rocks is expressed in the following equation based on the data of cores, which are less susceptible to contaminants compared with sidewall cores and cuttings: T_max(℃)=46×Ro(%)+406.

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Tokyo metropolitan area adjoing Tokyo Bay is one of the most urbanized sites in the world. The purpose of this study is analyses of relationship between changes of biogenic organic compounds in sediments and human activities in Tokyo Bay during 20th century.
Changes of biogenic organic compounds in the sediments revealed three different patterns. (1) Lignin phenols and n-C₂₀-C₃₂ fatty acids derived from land higher plants have increased from a half of 1950's, and have decreased from a boundary of about 1970. (2) n-C₁₀-C₁₈ fatty acids and n-C_16:1, C_18:1 unsaturated fatty acids mainly derived from phytoplanton, and br-C₁₅, C₁₇ fatty acids derived from bacteria have increased from a half of 1960's, and have increased from about 1980 with a small peek of about 1970. (3) Coprostanol and epicoprostanol mainly derived from human fecal pollution have not detected at all before 1920, and have gone on increasing from a half of 1950's.
The histrical records of these biogenic organic compounds in the sediments during this century clearly indicate an advanced eutrophication of Tokyo bay.

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Recently, it has been shown that the sediments of some acid lakes in Japan (pH=3-5), for example, sediments from Lakes Tazawa-ko and Kussharo-ko, are containing characteristic lipids which include series of long-chain anteiso compounds. This study was undertaken to extend the organic geochemical research to a similar inorganically acid (pH=5) Lake Inawashiro-ko in Fukushima Prefecture, Japan. Analytical results revealed that the anteiso hydrocarbons were certainly detected in the upper layers above 10-12cm section of the sediment core taken from near the northwest coast (Core 3; length: 24cm; water depth 5m). However they were absent below the 14-16cm section. In the sediment core, relative proportion of diatom verbs of Cyclotella genis which favor neutral or alkaline water condition increased as the core depth increased. Hence the results were interpreted to indicate a pH decrease in the past to the present state of lake water.

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Wet precipitation (rain and snow) and aerosol samples were collected in Tokyo and analyzed for dicarboxylic acids (C₂-C₁₁), ω-oxocarboxylic acids (ωC₂-ωC₆), pyruvic acid and α-dicarbonyls (glyoxal and methylglyoxal) using a capillary GC and GC/MS. Molecular composition of dicarboxylic acids and related polar compounds in both wet precipctation and aerosol samples showed a strong seasonal trend. In the winter wet precipitation samples, longer chain dicarboxylic acids (C₆-C₉), unsaturated diacids and ketocarboxylic acids which are thought as intermediates of photochemical reactions were found to be relatively more abundant than the early summer samples. By contrast, oxalic acid (C₂) which has been proposed as an end product of photochemical chain reactions of anthropogenic and biogenic organic compounds was found to be more enriched in the early summer precipitations, suggesting that oxalic acid is more abundantly produced in the middle and upper troposphere. Similar seasonal trend was also found in the aerosol samples. This study suggested that the atmospheric photochemical reactions which are more active in early summer than in winter are imprinted in the molecular composition of dicarboxylic acids and related polar compounds in the wet precipitation and aerosol samples.

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We carried out heating experiments of chlorophyll-a alone and in the presence of clay or water in order to obtain useful information on its degradation in the early diagenesis in sediments. The heating experiments showed that the degradation proceeded in the order of chlorophyll-a with clay < chlorophyll-a alone < chlorophyll-a with water. The activation energies estimated were 36.2kcal/mol for chlorophyll-a alone, 38.3kcal/mol for chlorophyll-a with clay, and 21.0kcal/mol with water. The transformation pathway of chlorophyll-a to pyropheophorbide-a was different if water was present. Heating of chlorophyll-a alone and with clay released the phytyl chain in the first step, while demetallation preceded in case of chlorophyll-a with water.

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