{"title":"比利牛斯山脉中西部隆起低起伏地形分布中的主动断层控制","authors":"M. Ortuño, M. Viaplana-Muzas","doi":"10.1344/GEOLOGICAACTA2018.16.4.10","DOIUrl":null,"url":null,"abstract":"The activity of normal faults in the Central-Western Pyrenees is mainly detected by the disruption of paleic landforms surviving to Plio-Quaternary incision: the remnants of a Low-Relief Topography (LRT) that probably originated asynchronically during the Oligocene and Miocene. We propose a new method for mapping the LRT remnants that combines automatic analysis of digital topography and cross-checking with regional databases of Quaternary landforms. We focus on an area where the location of the main-drainage divide seems to be influenced by the activity of the Bedous-Pic de Midi du Bigorre set of faults and by the North Maladeta Fault. Neotectonic markers defined by the remnants of LRT envelops are tectonically displaced up to ~700m by the previously identified faults, but also along new faults observed in between them. A western prolongation of the North Maladeta Fault has been identified for the first time, implying a 75km total trace length, almost twice thepreviously published value. A restoration of the fault block motion was performed assuming a regional uplift across the range, enhanced in the northern part of the Axial Zone. This uplift leads to an outer arch extension along the Maladeta-Bedous Fault System. The resulting paleo-topography shows a broad southern paleo-flank (up to ~120km long) with a gentle regional gradient (~1o) and a much shorter and steeper northern paleo-flank (~4o gradient, up to 30km-long). This configuration suggests that the LRT remnants now located North of the main divide were connected to the Ebro Basin. The results are supported by previous studies on age and source provenance of major alluvial systems mantling the northern and southern flanks of the chain.","PeriodicalId":55107,"journal":{"name":"Geologica Acta","volume":null,"pages":null},"PeriodicalIF":1.3000,"publicationDate":"2018-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"10","resultStr":"{\"title\":\"Active fault control in the distribution of Elevated Low Relief Topography in the Central-Western Pyrenees\",\"authors\":\"M. Ortuño, M. Viaplana-Muzas\",\"doi\":\"10.1344/GEOLOGICAACTA2018.16.4.10\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"The activity of normal faults in the Central-Western Pyrenees is mainly detected by the disruption of paleic landforms surviving to Plio-Quaternary incision: the remnants of a Low-Relief Topography (LRT) that probably originated asynchronically during the Oligocene and Miocene. We propose a new method for mapping the LRT remnants that combines automatic analysis of digital topography and cross-checking with regional databases of Quaternary landforms. We focus on an area where the location of the main-drainage divide seems to be influenced by the activity of the Bedous-Pic de Midi du Bigorre set of faults and by the North Maladeta Fault. Neotectonic markers defined by the remnants of LRT envelops are tectonically displaced up to ~700m by the previously identified faults, but also along new faults observed in between them. A western prolongation of the North Maladeta Fault has been identified for the first time, implying a 75km total trace length, almost twice thepreviously published value. A restoration of the fault block motion was performed assuming a regional uplift across the range, enhanced in the northern part of the Axial Zone. This uplift leads to an outer arch extension along the Maladeta-Bedous Fault System. The resulting paleo-topography shows a broad southern paleo-flank (up to ~120km long) with a gentle regional gradient (~1o) and a much shorter and steeper northern paleo-flank (~4o gradient, up to 30km-long). This configuration suggests that the LRT remnants now located North of the main divide were connected to the Ebro Basin. 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引用次数: 10
摘要
中-西比利牛斯山脉正断层的活动主要是通过保存到上新世-第四纪切口的苍白地貌的破坏来检测的:低起伏地形(LRT)的残余,可能在渐新世和中新世异步起源。我们提出了一种绘制LRT遗迹的新方法,该方法结合了数字地形的自动分析和与第四纪地形区域数据库的交叉检查。我们关注的区域主要排水分水岭的位置似乎受到Bedous Pic de Midi du Bigorre断层和North Maladeta断层活动的影响。LRT包络残余物定义的新构造标志物被先前确定的断层构造位移高达~700m,但也沿着它们之间观察到的新断层位移。首次确定了北马拉德塔断层的西部延伸,这意味着总迹线长度为75km,几乎是之前公布值的两倍。假设整个范围内存在区域隆起,轴向带北部增强,则对断块运动进行了恢复。这种隆起导致了沿着Maladeta Bedous断层系统的外拱形延伸。由此形成的古地形显示了一个宽阔的南部古侧翼(长达约120km),具有平缓的区域梯度(约1o)和一个更短、更陡的北部古侧翼(约4o梯度,长达30km)。这种配置表明,现在位于主分水岭以北的LRT遗迹与Ebro盆地相连。这一结果得到了先前对覆盖该链南北两侧的主要冲积系统的年龄和来源的研究的支持。
Active fault control in the distribution of Elevated Low Relief Topography in the Central-Western Pyrenees
The activity of normal faults in the Central-Western Pyrenees is mainly detected by the disruption of paleic landforms surviving to Plio-Quaternary incision: the remnants of a Low-Relief Topography (LRT) that probably originated asynchronically during the Oligocene and Miocene. We propose a new method for mapping the LRT remnants that combines automatic analysis of digital topography and cross-checking with regional databases of Quaternary landforms. We focus on an area where the location of the main-drainage divide seems to be influenced by the activity of the Bedous-Pic de Midi du Bigorre set of faults and by the North Maladeta Fault. Neotectonic markers defined by the remnants of LRT envelops are tectonically displaced up to ~700m by the previously identified faults, but also along new faults observed in between them. A western prolongation of the North Maladeta Fault has been identified for the first time, implying a 75km total trace length, almost twice thepreviously published value. A restoration of the fault block motion was performed assuming a regional uplift across the range, enhanced in the northern part of the Axial Zone. This uplift leads to an outer arch extension along the Maladeta-Bedous Fault System. The resulting paleo-topography shows a broad southern paleo-flank (up to ~120km long) with a gentle regional gradient (~1o) and a much shorter and steeper northern paleo-flank (~4o gradient, up to 30km-long). This configuration suggests that the LRT remnants now located North of the main divide were connected to the Ebro Basin. The results are supported by previous studies on age and source provenance of major alluvial systems mantling the northern and southern flanks of the chain.
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