Late Cretaceous-Cenozoic Andean mountain building may have experienced various phases of orogenesis in response to variations the dip angle of the subducting slab, distinct magmatic pulses, and shortening rates of the orogen. The timing of the Eastern Cordillera (EC) erosion and the relationship between the Andean orogenesis and the establishing of the transcontinental Amazon River remains unclarified. The erosional history of the Amazon Andes and the timing of these orogenic events may be revealed by the late Cretaceous-Cenozoic sedimentary record of the Amazonian retroarc foreland basin. We investigate the provenance of the Maastrichtian-Cenozoic deposits of the Huallaga Basin based on major and trace elements concentrations, SmNd isotopic composition, and UPb zircon dating. We also refined the Oligocene paleoenvironment and calculated Paleogene sedimentation rates. Our results show that despite the 25 Myr-long sedimentary hiatus, both the Maastrichtian and Eocene units show dominant sourcing from the magmatic arc of the Western Cordillera (WC). Increases in Paleozoic and Famatinian zircon grains and a shift toward more negative ƐNd(0) values, indicate dominant EC sources during the Oligocene to middle Miocene. This change in provenance area is Rupelian in age based on the Maximum Likelihood Age (MLA) of JUA22 (29.70 ± 0.62 Ma), suggesting that the onset of Peruvian EC erosion started at ∼30 Ma. The erosion of the EC was accompanied by an increase in sedimentation rates and the development of a meandering fluvial system. Finally, a substantial decrease in zircon grains derived from the Cretaceous and Cenozoic Andean arcs from late Miocene to Recent sediments suggests no contribution of the WC. In contrast, an increase in Paleozoic magmatic arc zircon grains indicates sources in the EC. We compare our findings to constrain the erosional history of the Amazonian Andes and investigate the relationship between the timing of EC uplift and the onset of the transcontinental Amazon drainage system during the Cenozoic.

中文翻译：

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秘鲁北部亚马逊安第斯山脉的马斯特里希-新生代侵蚀历史对东科迪勒拉山脉演化的影响（秘鲁北部瓦拉加盆地）


晚白垩纪-新生代安第斯山脉建筑可能经历了造山的不同阶段，以响应俯冲板的倾角变化、不同的岩浆脉冲和造山带的缩短速率。东科迪勒拉山脉 （EC） 侵蚀的时间以及安第斯造山运动与跨大陆亚马逊河形成之间的关系仍未阐明。亚马逊安第斯山脉的侵蚀历史和这些造山事件的时间可能由亚马逊逆弧前陆盆地的晚白垩纪-新生代沉积记录揭示。我们根据主量和微量元素浓度、SmNd 同位素组成和 UPb 锆石测年法研究了 Huallaga 盆地马斯特里希-新生代矿床的来源。我们还完善了渐新世古环境并计算了古近纪沉积速率。我们的结果表明，尽管有 25 Myr 长的沉积中断，但马斯特里赫和始新世单元都显示出来自西科迪勒拉山脉 （WC） 岩浆弧的主要来源。古生代和法马提尼亚锆石颗粒的增加以及向更负的 ƐNd（0） 值的转变，表明渐新世至中新世期间主要的 EC 来源。根据 JUA22 的最大似然年龄 （MLA） （29.70 ± 0.62 马），这种种源区域的这种变化是 Rupelian 的年龄，这表明秘鲁 EC 侵蚀的开始始于 ∼30 马。EC 的侵蚀伴随着沉积速率的增加和蜿蜒河流系统的发展。最后，从中新世晚期到近期沉积物，白垩纪和新生代安第斯弧衍生的锆石颗粒大幅减少，表明 WC 没有贡献。 相比之下，古生代岩浆弧形锆石颗粒的增加表明 EC 中的来源。我们比较了我们的发现，以限制亚马逊安第斯山脉的侵蚀历史，并研究了 EC 隆起的时间与新生代跨大陆亚马逊排水系统开始之间的关系。