Paleoceanography and distribution of petroleum source rock in Japan based on calcareous nannofossils assemblages analysis

我们对从印度洋到西太平洋的深海岩心中发现的钙质超微化石组合进行了详细研究，以重建该地区中新世中晚期的古海洋学。结果表明，中新世中期，印度洋与太平洋的联系停止，海洋条件发生了剧烈变化。对日本中新统钙质超微化石组合的分析表明，新泻和秋田地区的沉积盆地均呈现出北西-东南和北东-西南的构造走向。日本海沿岸的这些古地理与表明有机质沉积的上升流的发生有很强的关系。根据钙质纳米化石组合分析的古新世条件，石油源岩可能沉积在新泻地区的长冈和北神原地区以及秋田地区沿北百里逆冲断层的日本海岸。

We studied in datil of the calcareous nannofossils assemblages found in the Deep Sea cores from Indian to western Pacific Ocean for reconstuction of paleoceanography of the area in the middle to late Miocene. The results indicate that the connection between the Indian and pacific Oceans was stopped during middle Miocene, and drastic changes of oceanographic conditions were occurred during this age. The analysis of calcareous nannofossils assemblages from Japanese Miocene series indicates that the sedimentary basin in both Niigata and Akita area was outlined by NW-SE and NE-SW structural trends. These paleogeography of the Japan Sea Side is stronglu related to occurrence of upwellings which indicate the deposition of organic matters.On the basis of the Paleocenographic conditions based on the analysis of calcareouys nannofossi assemblages, the petroleum source rocks would be deposited in the Nagaoka and Kita-Kanbara area in Niigata area, and the Coast of Japan Seaside along the Kitayuri thrusts faults in Akita area.