RUI: Collaborative Research: Reconstructing Mid-Miocene-to-Recent Paleo-Erosion Rates in the Eastern Andes, Northern Argentina

气候条件和构造变形都已知会影响侵蚀速率，尽管对侵蚀速率随时间变化的反应仍知之甚少。这个问题一直难以解决，因为缺乏可靠的替代数据，可以定义过去的侵蚀速率，记录速率变化的时间尺度可比的重大变化，在气候和构造。 例如，当使用侵蚀沉积物中宇宙成因核素的浓度来评估现代速率时，这些速率通常反映千年时间尺度上的侵蚀，而山区带的侵蚀速率通常是在许多气候周期平均的百万年时间尺度上评估的。通过在阿根廷东安第斯山脉建立一个约1000万年的古侵蚀速率记录，我们将探索气候和变形之间的权衡，因为它们调节侵蚀。我们将测量三种不同的宇宙成因同位素（10 Be，21 Ne和26 Al）在古代河流沉积物中沉积在安第斯山麓。这项研究将利用人类在1900年左右无意中造成的独特暴露，人类将部分河流转移到灌溉渠中，并引发了大规模的侵蚀事件，在过去的100年里，该事件已经切割了一条100米深，10公里长的通道。 在丛林中，这个切口揭示了过去1000万年来从安第斯山脉侵蚀而来的约7公里厚的沉积物的原始暴露。重要的是，这种暴露是理想的宇宙成因研究过去的侵蚀率，它提供了极好的年龄控制通过其已经建立的记录地球的逆转？的磁场和火山灰，可以精确地定年。 使用三种具有不同半衰期和宇宙成因生产率的同位素，将大大减少与沉积物储存、再循环和同沉积暴露有关的不确定性，并将为侵蚀率的更稳健历史奠定基础。 多同位素的方法，配合碎屑锆石分析，也可能提供一个机会，建立一个地层记录的沉积物埋藏和再动员的集水区。当与气候和构造隆起的区域记录配对时，由此产生的侵蚀和沉积物输送记录应该为景观演变的数值模型提供有价值的约束。 该项目还将扩大稳定的21 Ne的应用范围，并探索其可靠地记录超过10 Be自然衰变所施加的限制的侵蚀速率的能力。山区地带的侵蚀速率与驱动这种侵蚀的外部因素之间的关系是我们理解现代和古代地质系统的关键。 例如，预测气候引起的山脉侵蚀率变化可以为社会对全球气候变化影响的准备提供信息。 同样，对气候和侵蚀之间长期联系的研究可以帮助地质学家了解古代山脉的命运及其在地球历史中的作用。 该项目将代表宇宙成因同位素定年的一种新应用：一种计算地球附近岩石停留时间的技术？通过测量宇宙射线与地球上的岩石和矿物质碰撞时产生的稀有同位素，s表面。成功地解决与将这种类型的测年应用于古代沉积物相关的许多挑战，将有助于为在更古老的沉积物中提出类似的问题奠定基础，这些沉积物记录了人们对地球时期知之甚少。这是更古老的历史。 该项目将帮助培训下一代科学家，让他们接触最先进的同位素地球化学技术，并发展解释地球所需的技能。的沉积记录。 通过在国际环境中将高级PI与初级研究人员以及研究生与本科生配对，该项目将促进各种技能和经验水平的连续培训。

Both climatic conditions and tectonic deformation are known to influence rates of erosion, although the response of erosion rates to changes in these controling mechanisms over time is still poorly understood. This question has been difficult to address due to a lack of reliable proxy data that can define past erosion rates that record rate changes over timescales comparable to significant changes in climate and tectonics. For example, when modern rates are assessed using the concentrations of cosmogenic nuclides in eroded sediments, those rates typically reflect erosion on millennial timescales, whereas erosion of mountain belts rates is typically assessed at million-year time scales that average across many climate cycles. By developing a ~10-million-year-long record of paleo-erosion rates in the Eastern Andes of Argentina, we will explore the trade-offs between climate and deformation as they modulate erosion. We will measure three different cosmogenic isotopes (10Be, 21Ne, and 26Al) in ancient river sediments that were deposited in the Andean foothills. This study will capitalize on a unique exposure that was inadvertently created by humans who, in about 1900, diverted part of a river into an irrigation ditch and triggered a massive erosional event that has cut a channel over 100 m deep and 10 km long in the past 100 years. In the midst of the jungle, this incision has revealed a pristine exposure of a ~7-km thickness sediments eroded from the Andes over the past 10 million years. Importantly, this exposure is ideal for cosmogenic studies of past erosion rates, and it offers superb age control via its already establish record of reversals of Earth?s magnetic field and volcanic ashes that can be precisely dated. Using three isotopes with different half-lives and cosmogenic production rates will allow significant reduction of uncertainties associated with sediment storage, recycling, and syn-depositional exposure, and will underpin a more robust history of erosion rates. The multi-isotope approach, paired with detrital zircon analyses, may also provide an opportunity to establish a stratigraphic record of sediment burial and remobilization within the catchment. When paired with regional records of climate and tectonic uplift, the resulting erosion and sediment transport records should provide valuable constraints for numerical models of landscape evolution. The project will also broaden the scope of applications for stable 21Ne and serve as an exploration of its ability to reliably record erosion rates beyond the limits imposed by natural decay of 10Be.The relationship between rates erosion in mountain belts and the external factors that drive this erosion is key to our understanding of both modern and ancient geologic systems. For example, predicting climate-induced changes in erosion rates from mountain ranges can inform societal preparedness for the effects of global climate change. Likewise, studies of the long-term linkage between climate and erosion can help geologists understand the fate of ancient mountain belts and their role in Earth history. This project will represent a novel application of cosmogenic isotope dating: a technique that computes the residence time of rocks near the Earth?s surface by measuring rare isotopes produced when cosmic rays collide with rocks and minerals at the Earth?s surface. Success in addressing the many challenges associated with applying this type of dating to ancient sediments will help lay the foundation for asking similar questions in even older sediments, which record poorly understood periods of Earth?s much older history. The project will help to train the next generation of scientists by exposing them to cutting-edge isotope geochemistry techniques and by developing the skills necessary to interpret Earth?s sedimentary record. By pairing a senior PI with junior investigators, as well as graduate students with undergraduates in an international setting, the project will promote a continuum of training across a variety of skill sets and experience levels.