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Climate or tectonics? What controls the spatial-temporal variations in erosion rates across the Eastern Cordillera of Colombia?
Global and Planetary Change ( IF 3.9 ) Pub Date : 2021-06-11 , DOI: 10.1016/j.gloplacha.2021.103541
Helbert García-Delgado , Nicolás Villamizar-Escalante , Mauricio A. Bermúdez , Matthias Bernet , Francisco Velandia

Linking the long-term with the short-term exhumation history of a mountain range is vital for understanding the evolution of orogenic topography. Further, erosion rates could be controlled by the variability of climatic and/or tectonic processes over geological time. For example, in the Eastern Cordillera of the Colombian Andes, until recently climate forcing has been hypothesized as the primary driver of rapid Pliocene exhumation rates. In this contribution, we test this climate forcing hypothesis by integrating geomorphic, seismic, geological and published low-temperature thermochronological (Apatite Fission-Track; AFT), and cosmogenic nuclide (CN) data to quantitatively test the correlation of the spatial patterns of exhumation/erosion with either a tectonic or climatic forcing. From a regional perspective, both the long- and short-term erosion rates (derived from AFT and CN data, respectively) have a reasonable correlation with the seismic strain rates and local relief, whereas the contribution of the short-term rainfall patterns to exhumation (and denudation) is either weak or non-existent. For the Eastern Cordillera, tectonism through seismic deformation therefore seems to be a more critical driver of the topographic evolution of the range when compared with the climate variable. To deepen our investigation, we subdivided the study area into six subregions and performed a detailed statistical analysis. In one out of the six subregions (SEC2E), in the Quetame Massif area, short-term rainfall data is well correlated with the computed erosion rates. Nevertheless, the ten-fold difference between the long-term (2.36 km/Myr) and the current (0.27 km/Myr) denudation rates suggest they are strongly decoupled. The remaining five subregions featured varied correlations suggesting that the tectonic-climatic characteristics of each area must be considered and that effective local controls, such as rainfall in subzone SEC2E, cannot be extrapolated to the whole range. Finally, we discuss the tectonic implications of our findings, stressing how tectonic inheritance, typical of inversion orogens such as the Eastern Cordillera, is critical for understanding the spatial variability in exhumation/erosion rates and surface uplift. For instance, we reconstructed the paleoprofiles of four rivers (the Duda, Ariari, Guayuriba, and Guatiquía Rivers), draining the Sumapaz and Chingaza relict landscapes, on the hanging wall of the Servitá Fault, the typical example of an inverted structure. In this way, we evidenced a net surface uplift of at least 1.4 km since the late Miocene, which we speculate primarily controlled by the Servitá Fault. These findings have first-order implications as they provide evidence for Pliocene to Pleistocene landscape rejuvenation driven by tectonically inverted faults.



中文翻译:

气候或构造?是什么控制了哥伦比亚东部山脉侵蚀率的时空变化?

将山脉的长期与短期挖掘历史联系起来对于理解造山地貌的演变至关重要。此外,侵蚀率可以通过地质时期气候和/或构造过程的可变性来控制。例如,在哥伦比亚安第斯山脉的东部山脉,直到最近,气候强迫一直被假设为上新世快速挖掘率的主要驱动因素。在这篇文章中,我们通过整合地貌、地震、地质和已发表的低温热年代学(磷灰石裂变轨迹;AFT)和宇宙成因核素 (CN) 数据来测试这种气候强迫假设,以定量测试剥脱空间模式的相关性/ 具有构造或气候强迫的侵蚀。从区域来看,长期和短期侵蚀率(分别来自 AFT 和 CN 数据)与地震应变率和局部地势具有合理的相关性,而短期降雨模式对挖掘(和剥蚀)的贡献是要么弱,要么不存在。因此,对于东科迪勒拉山脉,与气候变量相比,地震变形引起的构造作用似乎是该地区地形演变的更关键驱动因素。为了深入调查,我们将研究区域细分为六个分区,并进行了详细的统计分析。在六个子区域中的一个 (SEC2E) 中,在 Quetame Massif 地区,短期降雨数据与计算出的侵蚀率密切相关。尽管如此,长期 (2.36 km/Myr) 和当前 (0. 27 km/Myr) 剥蚀率表明它们是强解耦的。其余五个子区域具有不同的相关性,这表明必须考虑每个区域的构造气候特征,并且不能将有效的局部控制(例如 SEC2E 子带的降雨量)外推到整个范围。最后,我们讨论了我们的发现对构造的影响,强调了构造继承(东科迪勒拉等反转造山带的典型特征)对于理解剥脱/侵蚀速率和地表抬升的空间变异性至关重要。例如,我们在 Servitá 断层的挂壁上重建了 4 条河流(杜达河、阿里阿里河、瓜尤里巴河和瓜蒂基亚河)的古剖面,这些河流排水了苏马帕斯河和钦阿萨河遗迹景观,这是倒置结构的典型例子。这样,自中新世晚期以来,我们证明了至少 1.4 公里的净地表抬升,我们推测这主要由 Servitá 断层控制。这些发现具有一阶意义,因为它们为由构造倒置断层驱动的上新世至更新世景观复兴提供了证据。

更新日期:2021-06-15
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