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Late Cenozoic microbiostratigraphy and development of sedimentary basins in the Akita oil-fields.

秋田油田晚新生代微生物地层与沉积盆地发育.

基本信息

批准号：
03640651
负责人：
MATOBA Yasumochi
金额：
$ 1.15万
依托单位：
Akita University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1991
资助国家：
日本
起止时间：
1991 至 1992
项目状态：
已结题

项目摘要

The late Cenozoic stratigraphic scheme of the Akita oil field was established in 1928 and has long been accepted by many geologists until recently without great changes. It is a composit succession of formations of the Oga and the Akita City areas: the Onnagawa, Fumakawa, Tentokuji, and Sasaoka Formations in ascending order. Thus the correlation of strata between both areas is the fundamental of this scheme.The Onnagawa and Funakawa Formations whose types are in the Oga Peninsula have been widely applied in the Akita oil fields. Diatom biostratigraphy was examined in the two formations in several areas in the Akita oil fields. The results demonstrate that the Onnagawa Formation distributed in the inland area, east side of the present Akita coast, is correlated with the lower to middle part of the same formation of Oga, and the Funakawa of the inland area with the upper part of the same formation of the Oga Peninsula.The Tentokuji and Sasaoka Formations, with their types in the Akita City area, have long been correlated with the Kitaura and Wakimoto Formations of Oga. The studies on diatom, planktonic foraminifera, and calcareous nannofossil of the Tenntokuji and Sasaoka Formations from several inland areas revealed that the two formations can be correlated with the Funakawa Formation of the Oga Peninsula, not with the overlying Kitaura and Wakimoto Formations.According to these results, the Akita oil fields can be structurally devided into major areas separated by a line along the present Akita coast, where runs the Kitayuri thrust system. The east side of the thrust was rapidly uplifted during the deposition of the Sasaoka Formation and finally emerged. In contrast, in the western side of the thrust including the Oga Peninsula, a marine basin continued to exist, and the thick bathyal Kitaura and Wakimoto Formations were deposited. These results may reqire a future revision of a traditional concept of the structural deveropment of the Akita oil fields.

秋田油田的晚新生代地层系统建立于1928年，长期以来一直被许多地质学家所接受，直到最近才有大的变化。这是一个commonly继承的地层的OGA和秋田城市地区：Onnagawa，Fumakawa，Tentokuji和Sasaoka地层按升序排列。在秋田油田中，以大贺半岛为代表的翁长川组和船川组已得到广泛应用。对秋田油田几个地区的两个地层进行了硅藻生物地层学研究。结果表明，分布于现今秋田海岸东侧内陆地区的女长川组与大贺组中下部对应，分布于内陆地区的船川组与大贺半岛组上部对应，分布于秋田市区的天德寺组和佐冈组，一直以来都与大贺的北浦组和胁本组有关。通过对日本内陆几个地区的天德寺组和佐佐冈组的硅藻、浮游有孔虫和钙质超微化石的研究，发现这两个组与日本大贺半岛的船川组相对应，而与上覆的北浦组和胁本组不相对应。根据这些结果，秋田油田在构造上可以沿着现今的秋田海岸线划分为几个主要区域。北里推进系统的运行地点逆冲断层东侧在佐冈组沉积过程中迅速抬升，最终露出。相反，在冲断带的西侧，包括Oga半岛，海洋盆地继续存在，并沉积了厚的半深海Kitaura和Wakimoto组。这些结果可能需要对秋田油田构造演化的传统概念进行修正。