白亜系手取層群の砂岩・泥岩に含まれる炭酸塩鉱物の炭素・酸素同位体比

概要

論文の詳細を見る
Carbon and oxygen isotopic ratios were measured for calcite contained in calcareous sandstone and shale in the Kuwashima Formation of the Cretaceous Tetori Group. The δ ^<18>O values for the calcite from the formation range from 10.9 to 15.9‰ vs. SMOW, which values are remarkably lower than those of marine limestone. Since there is evidence for believing that post-depositional oxygen isotopic alteration in calcite did not occur in the Tetori Group, the low δ ^<18>O values obtained in this study are interpreted as being due to the result of calcite precipitation from fresh water. The studies on sedimentary facies and those on the fossils contained in the formation are in harmony with the above interpretation. The precipitation of calcite in the Kuwashima Formation must be ascribed to the results of microbial methanogenesis during diagenesis of organic-rich sediments.
地学団体研究会の論文
2002-01-25