| 鄂尔多斯盆地西缘李105井奥陶系乌拉力克组笔石生物地层研究 |
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| 关键词:the western margin of the Ordos Basin Wulalike Formation graptolite biozone diachronous Well Li-105 |
| 基金项目:国家自然科学基金项目(编号: 42172038)；中国地质调查局地质调查项目(编号: DD20230006) |
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| The Graptolite Biostratigraphy of the Wulalike Formation, Ordovician from Well Li-105 in the Western Margin of the Ordos Basin |
| Based on a study of the graptolite fauna in the Ordovician Wulalike Formation of Well Li-105 in the western margin of the Ordos Basin, two graptolite biozones are recognized, the Nemagraptus gracilis and Climacograptus bicornis biozones. The Wulalike Formation in this area is referred to as Sandbian (Late Ordovician). The base of the Wulalike Formation, originally marked by a set of characteristic conglomerate limestones, is not a proper definition based on sedimentological characteristics and the latest progress in the lithofacies and paleogeography of the Wulalike Formation. The black graptolite-bearing shales in the upper part of the Kelimoli Formation may have been incorporated into the Wulalike Formation. The newly defined Wulalike Formation contains at least three graptolite biozones: the Pterograptus elegans, Didymograptus murchisoni, and Nemagraptus gracilis biozones in the Wuhai Zhuozishan area of Inner Mongolia, based on the study of the graptolite faunas from the typical sections. The formation time interval ranged from the late Darriwilian of the Middle Ordovician to the early Sandbian of the Late Ordovician. Consequently, the base and top boundaries of the formation are diachronous from the outcrops to the subsurface areas in the western margin of the Ordos Basin. The study of the graptolite fauna from Well Li-105 provides precise biostratigraphical constraints for the time interval of the Wulalike Formation and its facies changes with diachronous base and top boundaries. In addition, this study will benefit not only the reconstruction of the lithofacies and paleogeography in this area but also help optimize the favorable facies zone for shale gas exploration. |
| WANG Chuanshang,HU Yong,Jörg MALETZ,WEI Kai.2025.The Graptolite Biostratigraphy of the Wulalike Formation, Ordovician from Well Li-105 in the Western Margin of the Ordos Basin[J].Acta Geoscientica Sinica,46(2):273-282. |
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