Veleda A. P. Muller, Christian Sue, Pierre G. Valla, Pietro Sternai, Thibaud Simon-Labric, Cécile Gautheron, Kurt M. Cuffey, Djordje Grujic, Matthias Bernet, Joseph Martinod, Matias C. Ghiglione, Peter Reiners, Chelsea Willett, David Shuster, Frédéric Herman, Lukas Baumgartner, Jean Braun
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引用次数: 0
Abstract
High-relief glacial valleys shape the modern topography of the Southern Patagonian Andes, but their formation remains poorly understood. Two Miocene plutonic complexes in the Andean retroarc, the Fitz Roy (49°S) and Torres del Paine (51°S) massifs, were emplaced between 16.9–16.4 Ma and 12.6–12.4 Ma, respectively. Subduction of oceanic ridge segments initiated ca. 16 Ma at 54°S, leading to northward opening of a slab window with associated mantle upwelling. The onset of major glaciations caused drastic topographic changes since ca. 7 Ma. To constrain the respective contributions of tectonic-mantle dynamics and fluvio-glacial erosion to rock exhumation and landscape evolution, we perform inverse thermal modeling of a new data set of zircon and apatite (U-Th)/He from the two massifs, complemented by apatite 4He/3He data for Torres del Paine. Our results show rapid rock exhumation recorded only in the Fitz Roy massif between 10 and 8 Ma, which we ascribe to local mantle upwelling forcing surface uplift and intensified erosion around 49°S. Both massifs record a pulse of rock exhumation between 7 and 4 Ma, which we interpret as enhanced erosion during the beginning of Patagonian glaciations. After a period of erosional and tectonic quiescence in the Pliocene, increased rock exhumation since 3–2 Ma is interpreted as the result of alpine glacial valley carving promoted by reinforced glacial-interglacial cycles. This study highlights that glacial erosion was the main driver to rock exhumation in the Patagonian retroarc since 7 Ma, but that mantle upwelling might be a driving force to rock exhumation as well.
高凸冰川谷塑造了南巴塔哥尼亚安第斯山脉的现代地形,但人们对它们的形成却知之甚少。安第斯弧后部的两个中新世火山岩群,即菲茨罗伊(南纬 49°)和托雷斯德尔帕恩(南纬 51°)岩块,分别在 16.9-16.4 Ma 和 12.6-12.4 Ma 之间形成。大洋脊段的俯冲开始于南纬 54°,约 16 Ma,导致板块窗口向北打开,并伴有地幔上涌。自约 7 Ma 开始的大冰川作用导致了地形的急剧变化。7 Ma。为了确定构造-地幔动力学和河流-冰川侵蚀作用各自对岩石掘起和地貌演变的贡献,我们对来自这两个山丘的锆石和磷灰石(U-Th)/He新数据集进行了逆热建模,并对托雷斯德尔潘恩的磷灰石4He/3He数据进行了补充。我们的研究结果表明,只有菲茨罗伊山丘在10-8Ma之间记录到了快速的岩石掘起,我们将其归因于当地地幔上升流迫使地表隆起和南纬49°附近的侵蚀加剧。两个山丘都记录了 7 至 4 Ma 之间的岩石掘起,我们将其解释为巴塔哥尼亚冰川期开始时侵蚀作用的加强。在经历了上新世时期的侵蚀和构造静止期之后,自 3-2 Ma 以来岩石掘出量的增加被解释为冰川-间冰期循环加强所导致的高山冰川峡谷开凿的结果。这项研究强调,冰川侵蚀是巴塔哥尼亚后弧自7Ma以来岩石掘出的主要驱动力,但地幔上升流也可能是岩石掘出的驱动力。
期刊介绍:
Tectonics (TECT) presents original scientific contributions that describe and explain the evolution, structure, and deformation of Earth¹s lithosphere. Contributions are welcome from any relevant area of research, including field, laboratory, petrological, geochemical, geochronological, geophysical, remote-sensing, and modeling studies. Multidisciplinary studies are particularly encouraged. Tectonics welcomes studies across the range of geologic time.