1) Sedimentary basins in Akita region are divided into several structural basins, and there are many oil fields. The existence of these oil fields is closely related to the genetic process of these structural basins appeared on shelf zone in the Miocene.
2) The extractable organic matter of mudstones increases toward the geologically lower horizon and shows two prominent peaks; one is in the Onnagawa formation and the other in the lower part of the Tentokuji formation. The main productive reservoirs have been discovered in both formations.
3) The resemblance of each reservoir conditions of various fields suggests similarity in genetic process of most oil fields.
4) Growth of each oil field structure occurred concurrently with volcanic activity.
5) Therefore, it is concludcd that most structural traps were formed at about the time of the organic movement which occurred soom after the deposition of the formation containing main reservoirs.
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