始新世鄂尔多斯盆地周缘裂陷解体事件在宁南地区的响应

Response of the Ningnan Area to the Eocene Peripheral Rifting Breakup Event of the Ordos Basin

关于鄂尔多斯盆地自晚白垩世以来所经历的多阶段后期改造的研究，长期以来备受关注但所取得的认识和研究程度不一，尤其是对于始新世时期的周缘裂陷解体事件的研究尤为薄弱。针对这一现状，选取鄂尔多斯盆地西缘中部香山地区进行磷灰石裂变径迹分析，试图寻找其新生代冷却-抬升的低温热年代学记录，并探讨其与始新世鄂尔多斯盆地周缘裂陷解体事件的联系。研究表明，香山地区普遍存在始新世（45．4～40．8Ma）及晚白垩世（88．8～74．1Ma）两期年龄，而香山地区所记录的始新世裂变径迹年龄则反映出与鄂尔多斯盆地周缘裂陷解体事件密切相关；结合宁南地区大量的野外露头观测、地震剖面分析及实验测试．认为新生代宁南盆地与银川盆地、渭河盆地、河套盆地等断陷盆地的形成时间统一、背景一致，均形成于张性断陷环境之中，属干鄂尔多斯盆地周缘裂陷解体事件的一部分。

Multi-stage late reformations have occurred in the Ordos Basin since the Late Cretaceous. For a long time, experts have paid much attention to this issue but few consensus have achieved, especially the study of the Eocene peripheral rifting breakup event. In view of this situation, this paper is designed to take the Xiangshan area, located in the middle part of the west margin of Ordos Basin, as the research object to discuss its relationship with the peripheral rifting breakup event of the Ordos Basin. In this study apatite fission track （AFT） is used for the analysis, and the results show that the Eocene 45.4-40.8 Ma and Late Cretaceous 88.8-74.1 Ma ages are widely recorded in the Xiangshan area while the Eocene AFT ages are closely related to the peripheral rifting breakup event of the Ordos Basin. Considering that the Xiangshan area is the northwest margin of the Ningnan Basin, we combine the AFT ages with field investigations and seismic sections and believe that the formation of Ningnan Basin has the same time and background with the Yinchuan Basin, Weihe Basin and Hetao Basin. Hence, this basin belongs to a part of the peripheral rifting breakup event of the Ordos Basin.