Study on the system of deposition of organic matter in fore-arc basin and accretionary prism during Paleogene and Neogene

2004-2006年，为了明确弧前盆地有机质沉积体系和增生棱柱，我们对四冈县Kakegawa地区、MITI“Sagara”（岩屑）和室户半岛Shimant地区的泥岩、油类、细菌和微化石进行了研究。研究结果如下：巨型背斜西北部的原油主要含高成熟芳烃和低成熟甾烷和藿烷。背斜东南方的甾烷和藿烷油成熟程度较高。这些结果表明，该油可能被另一种不同成熟度的油污染。2. 三仓群下中新统松洼组硅质泥岩为较好的潜在烃源岩（TOC=0.9%, S2=约2.8 mghc / rock， HI=约a. a）。350mgHC/gC)在Kakegawa地区，但在MITI“Sagara”近海地区没有显示出良好的潜力。3. 古近纪和新近纪的升温速率在Kakegawa地区较高，在MITI“Sagar…More a”地区较低。只有古近系三仓群到达深部，形成了凝析油。4. 基于盆地模拟（basin - mod）的计算机模拟，萨加拉油田弧前盆地在29Ma （Mikura组）和15Ma （Kurami组）生油，然后在2ma （Mikura组）生凝析油。5. Mikura组的凝析油在运移过程中会污染Kurami组的原油，从而从源层运移到Megami圈闭。6. 钙质纳米浮游生物化石为Sphenolithus heteromorphus、Hericosphaera ampliaperta等11种，表明西igo群中下游时代为CN3带（18.2 ~ 15.6 Ma）。7. 在萨加拉油中未发现细菌HD-1，说明HD-1不能产生萨加拉油的主要成分。发现了甲苯细菌。8. Muroto半岛的增生棱镜显示，该地区白垩系海洋沉积了富有机质沉积物，但沉积物中含有大量陆相有机质。少

'2004-2006'In order to make clear the system of deposition of organic matter in fore-arc basin and accretionary prism, we investigated mud-rocks, oils, bacteria and micro-fossiles from Kakegawa area of Sizuoka prefecture, MITI "Sagara" (cuttings) and Shimant zone of Muroto Peninsula. Results are followings : 1. The oils from the northwest Megami anticline contained highly matured aromatic hydrocarbon and lowly matured steranes and hopanes. The oils from the southeast of the anticline steranes and hopanes were highly matured. These results suggest that the oil could be contaminated by another oil with different maturity. 2. Siliceous mudstones for the lower Miocene Matsuba Formation of Mikura Group showed a good potential source rock (TOC=0.9%, S2=c.a.2.8mgHC/gRock, HI=c.a.350mgHC/gC) in the Kakegawa area, but did not show a good potential in MITI "Sagara" from off shore area. 3. Heating rate during Paleogene and Neogene was high in the Kakegawa area and low in the off shore MITI "Sagar … More a" area. Only Paleogene Mikura Group reached to the deep zone which generated condensates. 4. Based on the computer simulation of basin modeling (Basin-Mod), the fore-arc basin in the Sagara oil field generated oils in 29Ma (the Mikura Group) and 15Ma (the Kurami Group), and then generated condensates in 2 Ma (the Mikura Group). 5. The condensate from the Mikura Group could migrated from source bed to the Megami trap with contamicating oils from the Kurami Group during migration. 6. Fossils of calcareous nannoplankton were Sphenolithus heteromorphus, Hericosphaera ampliaperta and the other 11 species suggested that the age of the middle-lower Saigo Group was CN3 zone (18.2-15.6 Ma). 7. Bacteria HD-1 was not found in the Sagara oils suggesting that HD-1 could not generate the main part of the Sagara oils. Toluene-bacteria was found. 8. In the accretionary prism from the Muroto Peninsula showed that organic rich sediments were deposited in Cretaceous ocean in this area, but the sediments contain a lot of terrestrial organic matter. Less