新甘交界北山地区早二叠世红柳河群的建立
Establishment of the Early Permian Hongliuhe Group in the Beishan area on the border region of Xinjiang and Gansu,China
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摘要: 经1：5万区域地质调查研究，北山地区原红柳河组规模巨大，岩性、岩相差异明显，按岩石地层划分原则，应进一步分组。原红柳河组内部有4套岩性、岩相差异较大的岩石组合，以3次砾岩事件和1次火山岩事件为标志，代表了4个不同的沉积阶段，与之对应出现了4个重要的沉积（不整合）界面。依据这4个界面对早二叠世红柳河组进行了重新划分，即下二叠统河西组（P1h）、红柳村组（P1hl）、芦苇井组（P1l）和红柳井组（P1hj）。在河西组采集到大量的腕足、苔藓虫等海相动物化石，在芦苇井组第二岩性段舍炭粉砂岩中获孢粉化石组合，其时代属于二叠纪。本区新建的4个组实际上是由一个规模较大的老组再分组的结果。按岩石地层单位修定的要求，建议原红柳河组上升为群。Abstract: The 1:50000 regional geological survey indicates that the original Hongliuhe Formation in the Beishan area is large in scale and shows marked differences in lithology and lithofacies. According to the principle of lithostratigraphic division, it should be subdivided into several formations. The original Hongliuhe Formation has four rock associations with notably different lithologies and lithofacies. They are marked by three conglomerate events and one subvolcanic event, representing four different stages of deposition, which correspond to four important unconformities. Based on the four unconformities, the Early Permian Hongliuhe Formation has been subdivided into the Lower Permian Hexi Formation (P1h), Hongliucun Formation (P1hl), Luweijing Formation (P1l) and Hongliujing Formation (P1hj). Plenty of marine animal fossils such as brachiopods and bryozoans have been collected in the Hexi Formation, and a Permian sporopollen assemblage has been obtained from carbonaceous siltstone in the Second Member of the Luweijing Formation. In fact, the four newly established formations are the result of subdivision of a larger-scale, older formation; so according to the requirements for the revision of lithostratigraphic units in the international stratigraphic guide, the authors suggest that the previously established Hongliuhe Formation should be raised to the group rank.
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Keywords:
- Early Permian /
- lithostratigraphic unit /
- Hongliuhe Group /
- Beishan, Gansu
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