| 西藏措勤盆地上侏罗统萨波直不勒组的发现及其烃源岩 |
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| 关键词:Coqen Basin Upper Jurassic Sabozhibule Formation strata redefinition oil-gas exploration |
| 基金项目:国家自然科学基金项目(编号: 41472030);科技基础性工作专项(编号: 2015FY310100);中国地质调查局基础性公益性矿产地质调查项目(编号: DD20160120-02; DD20160120-04; DD20160126);中国地质科学院基本科研业务费项目(编号: J1607) |
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| 摘要: |
| The Discovery of the Upper Jurassic Sabozhibule Formation in Coqen Basin, Tibet, and Its Source Rock |
| About 10 genera and 15 species or undefined species of coral fossils are recognized in the Gechangchayu section, eastern Coqen Basin, Baoji area, Bange County, Tibet. They are Actinaraea? sp., Allocoenia matheyi (Koby), Allocoenia? sp., Clausastraea? sp., Hydnophora? sp., Latiastraea minima (Koby), Latiastraea? sp., Meandraraea? sp., Stylosmilia crassitheca Liao et al Li, S. corallina Koby, Thamnasteria? sp., T. concinna (Goldfuss), Thecosmilia? sp., T. baojiensis sp. nov., Trocharaea cf. patelliformis Gregory. These corals indicate the age of related strata is Late Jurassic Oxfordian-Kimmeridgian. This section, which was used to be considered as middle Permian limestone blocks of Xiala Formation tectonically mixed in the middle Jurassic ophiolite complex, was redefined to Sabozhibule Formation based on both lithostratigraphic and biostratigraphic comparison in this study. The authors hold that there is no tectonic complex phenomenon happening among the Middle Permian Xiala Formation and the Middle Jurassic Ophiolite in this area. In addition, Gechangchayu section should be located far away from terrigenous detrital source area according to the fine-grained rock, more limestone interlayers and more abundant corals in comparison with the stratigraphic construction section in Qianggu Village, Wuma Town, Gaize County. All the evidence further proves that the sedimentary environment of Gangdese area gradually deepened from north to south during the Late Jurassic, the Coqen Basin was situated at an active pelagic-hemipelagic and slope facies sedimentary environment during the early time of Late Jurassic. There are 68m thick shales on the top of the Sabozhibule Formation, and the average TOC value is 0.83%, which indicates that they are medium- good source rocks. The TOC value of mudstone with the thickness of about 12 m at the 20th layer of Gechangchayu section is 0.65%, which belongs to the medium source rock. The top stratum is in the upper-slope facies, therefore its distribution range should be wider than the Tukari Formation. The calculated hydrocarbon generation quantity of source rocks in the Sabozhibule Formation is about 44.373×108 t within the whole Coqen Basin. Shale in the Sabozhibule Formation provides sufficient oil source for the Coqen basin, and the carbonate intercalations are also favorable reservoirs. It is suggested that sampling should be carried out in the Sabozhibule Formation to obtain more detailed and abundant organic geochemistry parameters. |
| SUN Qian,JI Zhan-sheng,LIAO Wei-hua,WU Gui-chun,HE Ji-fu,SHI Qiu-yuan,LI Hao,LIU Zhen-yu,GUO An-chen,HOU Zhao-shuo,LI Dong-ze,WAN Xiao-qiao.2018.The Discovery of the Upper Jurassic Sabozhibule Formation in Coqen Basin, Tibet, and Its Source Rock[J].Acta Geoscientica Sinica,39(4):432-444. |
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