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Cenozoic exhumation patterns in the northern Andes: Constraints from the southern Bucaramanga Fault, Eastern Cordillera, Colombia
Journal of South American Earth Sciences ( IF 1.8 ) Pub Date : 2021-07-24 , DOI: 10.1016/j.jsames.2021.103473
Francisco Velandia 1, 2 , Mauricio A. Bermúdez 3 , Barry Kohn 4 , Matthias Bernet 5 , Carlos A. Zuluaga 2 , Stephanie Brichau 6
Affiliation  

The left lateral strike-slip Bucaramanga Fault exhibits a transpressional southern termination located towards the axial zone of the Eastern Cordillera of Colombia, where the Boyacá and Soapaga Faults are also identified as inversion-related structures. To unravel their exhumation history, we obtained apatite and zircon fission-track and (U–Th)/He ages from samples collected along different structural domains, along five vertical profiles. Joint Bayesian inverse modeling of these data reveals at least four different episodes of cooling. These are: (i) 50 ± 5 Ma, (ii) 20 ± 5 Ma, (iii) 12 ± 3 Ma, and (iv) 5 ± 3 Ma. The earliest pulse is associated with reactivation of the Boyacá and Soapaga Faults. The second pulse is related to the transpressive reactivation along the southern termination of the Bucaramanga Fault and coincides with a marked increase in relief. The Miocene-Pliocene pulses are related to Bucaramanga Fault strike-slip reactivation. Older fission-track ages previously reported from other areas of the Santander Massif suggest migration of exhumation from north to south. The four cooling episodes identified in this study can be related, within a broader geodynamic context, to interaction between the Cocos, Nazca, Caribbean, and South American plates, and the accretion of large tectonic domains of different affinity (oceanic or continental) against the South American plate during the Cenozoic. Our results are consistent with previous work reported in the Santander Massif. The ages observed in the in-situ data correspond with the ages found in modern river sediments and support relief development from the Eocene to the present.



中文翻译:

安第斯山脉北部新生代挖掘模式:哥伦比亚东科迪勒拉布卡拉曼加断层南部的限制

左侧走滑布卡拉曼加断层在哥伦比亚东科迪勒拉的轴向区呈现出一个横向挤压的南部终点,在那里博亚卡和索帕加断层也被确定为与反转相关的构造。为了解开它们的挖掘历史,我们从沿五个垂直剖面沿不同结构域收集的样品中获得了磷灰石和锆石裂变轨迹和 (U-Th)/He 年龄。这些数据的联合贝叶斯逆建模揭示了至少四个不同的冷却事件。它们是:(i) 50 ± 5 Ma,(ii) 20 ± 5 Ma,(iii) 12 ± 3 Ma,和 (iv) 5 ± 3 Ma。最早的脉冲与博亚卡和索帕加断层的重新激活有关。第二个脉冲与沿布卡拉曼加断层南端的压压再激活有关,同时与地势的显着增加相吻合。中新世-上新世脉冲与布卡拉曼加断层走滑再激活有关。先前从桑坦德地块其他地区报道的较旧的裂变径迹年龄表明,挖掘物从北向南迁移。在更广泛的地球动力学背景下,本研究中确定的四个冷却事件可能与科科斯、纳斯卡、加勒比和南美板块之间的相互作用,以及具有不同亲和力(海洋或大陆)的大型构造域对新生代南美板块。我们的结果与先前在桑坦德地块中报道的工作一致。

更新日期:2021-07-30
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