Sequence stratigraphy and organic matter preservation of the Miocene to Pliocene Tatsunokuchi Formation, Iwate, Northeast Japan

Abstract

Sequence stratigraphic and organic matter analyses were carried out on the Miocene to Pliocene Ishibane, Tatsunokuchi and Motohata formations that occur in Kitakami City, Iwate, Northeast Japan. These formations consist of nine facies and a depositional sequence that formed during a rise and fall of sea level. The proportions of vitrinite and cutinite are high in fluvial deposits of the lowstand systems tract. The total organic carbon content and the proportion of NFA (non-fluorescent amorphous kerogen) increase with transgression, because the sedimentary environment changed into an estuary with bottom anoxia. The proportions of vitrinite and cutinite increase in the highstand systems tract. These phenomena indicate the strong influence of river discharge.