Organic geology of the Miocene muddy rocks in the Tsugaru basin, northern Honshu, Japan

概要

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Sixty-one outcrop samples of the Miocene muddy rocks from the Umanokamiyama area in the Tsugaru basin, Northern Honshu, were organic-geologically investigated to clarify their organic maturation, organic type and potential for petroleum source rock. The vitrinite reflectance (Ro) and the brightness of pollen (stTAI) indicate that the organic maturity of these rocks may be immature to the threshold of intense oil generation. The composition of visual kerogen shows that almost all samples have amorphous-type organic matter predominantly. The content of amorphous kerogen gradually increases in the interval from the Nagane to Umanokamiyama Formations, which suggests transgression. The abrupt increase, like a spike, of herbaceous kerogen, especially of Pinaceae pollen, was observed in the Genpachimori Formation. These phenomena were also found in the Miocene Odoji Formation of the Nakamuragawa route and the Miocene Odoji-Akaishi Formation of the MITI Nishi-Tsugaru-Oki borehole, although geological correlation by other microfossils has not been established between these formations. From the viewpoint of source rock evaluation, the Miocene muddy rocks in the Umanokamiyama area include a type of kerogen good for oil source and rich organic carbon, but have not undergone organic maturation for petroleum generation.
日本堆積学会の論文