Distribution of Recent benthic foraminifers in the interstitial waters with high methane and hydrogen sulfide contents

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This report discusses the relationship between the benthic foraminiferal assemblages and the chemical paleoenvironments with the cold seepage during the Late Cenozoic time. Benthic foraminiferal assemblages co-occurred with the peculiar molluscan assemblages, which were related with the Late Cenozoic cold seepage and were distributed in Miura Peninsula and the Kakegawa area, are examined by means of Q-mode factor analysis. The results of this analysis reveal the following chemically factors and the relationship between benthic foraminifers and molluscan taxa : (1) the chemical factors, which influences to the distribution of benthic foraminifers, are the hydrogen sulfide contents, methane contents, dissolved oxygen and alkalinity of the interstitial and bottom waters, (2) Bulimina aculeata, Bulimina striata, Hyalinea balthica and Nonionellina labradorica co-occur from the Calyptogena assemblage, (3) Rectoboliviana columellaris and Uvigerina proboscidea are found together with the Lucinoma assemblage, and (4) Nodosaria longiscata, Rectoboliviana cf.asanoi and Stilostomella lepidula are dominated in the samples yielding the Acharax assemblage.