| 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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| 引用本文：王传尚,胡勇,Jörg MALETZ,危凯.2025.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[J].地球学报,46(2):273-282. |
| DOI：10.3975/cagsb.2024.071901 |
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| 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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| 中文摘要:本文通过对鄂尔多斯盆地西缘李105井奥陶系乌拉力克组的笔石化石的研究, 划分出两个笔石生物带, 即Nemagraptus gracilis带和Cilmacograptus bicornis带, 其时限为桑比期。根据乌拉力克组的沉积学特征, 结合最新的岩相古地理研究进展, 认为原乌拉力克组的底界以一套特征的砾屑灰岩为标志欠妥, 建议将克里摩里组上段的以黑色含笔石页岩为主的地层划归乌拉力克组, 新厘定的乌拉力克组在盆地西缘北部露头区内蒙古乌海桌子山一带至少包含了Pterograptus elegans、Didymograptus murchisoni和Nemagraptus gracilis带等三个笔石带, 其时限跨越中奥陶世达瑞威尔期晚期到晚奥陶世桑比期早期。可见, 乌拉力克组在鄂尔多斯盆地西缘, 其顶、底界线均存在明显的穿时。这一发现不仅为乌拉力克组的时限及其相变穿时提供了准确的生物地层约束, 也为这一地区岩相古地理的重建及页岩气勘探有利相带的优选提供了依据。 |
| 中文关键词:鄂尔多斯盆地西缘 乌拉力克组 笔石带 穿时 李105井 |
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| The Graptolite Biostratigraphy of the Wulalike Formation, Ordovician from Well Li-105 in the Western Margin of the Ordos Basin |
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| Abstract: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. |
| keywords:the western margin of the Ordos Basin Wulalike Formation graptolite biozone diachronous Well Li-105 |
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