Genesis of the Western Slope of the Altiplano Plateau and Atacama Basin

冲断带与高山带斜坡的共同联系导致了一种普遍的假设，即地形起伏和地表缩短是内在联系的。例如，世界上许多大的山脉带都是双向的，发育良好的逆冲带背对着造山带的内部。然而，在一些关键的情况下，在没有主要断层的情况下，已经形成了显著的地形起伏。这些造山尺度的单斜及其沿走向的不连续性有可能阐明地壳力学和流变学对大陆造山作用的控制。 造山尺度单斜的一个特例发生在沿着安第斯山脉中部的阿尔蒂普拉诺-普纳高原的西部边界。虽然气候，特别是降水，对山区的形态有很大的影响，但在这个地区，气候输入被最小化，因为它是地球上最干燥的地方之一。严重缺乏降水导致地貌演变极其缓慢，并将地貌和地表的保存潜力从典型的山区几千年延长到数百万年。因此，高原西部边缘的形态反映了一个几乎纯粹的构造信号，使其成为旨在提高我们对大陆高原形成和造山作用的理解的研究的最合乎逻辑的起点。中新世到现在安第斯单斜隆起的年代学框架将从以下调查中得出：1）单斜趾部沉积盆地中堆积地层之间的几何关系，以及2）在深深切入单斜表面的一组水系中河流古梯度旋转程度的估计。将通过对保存在河谷中的阶地表面进行相关和高精度测量来确定古梯度。广泛的火山活动和大量的熔结凝灰岩喷发分布在整个新近纪的岩石记录，使现有的年代学的限制，可以通过识别和收集的火山物质测年。阿塔卡马盆地和塔玛鲁加尔盆地是进行露头和地震地层研究的理想野外地区。这两个盆地都位于单斜的山脚下，在水文上是封闭的。因此，它们保存了完整的新近纪沉积史。阿塔卡马盆地包含一个特别有价值的记录，因为它位于单斜最大的沿走向异常。确定盆地和单斜的偏转（时间和空间）之间是否存在成因联系将是一个重要的研究重点，因为它可能会产生对高原隆升过程的基本认识。这项研究是非常及时的，有可能是一个很好的贡献，了解表面过程，造山作用和高原隆升。这项工作的成果将通过测试单斜翘曲是否与造山带另一侧的变形同步，如安第斯山脉带和东科迪勒拉所示，推进目前关于高原隆起原因的知识。它还将测试在其他连续的山脉前沿的大地形异常的意义。本研究将探讨高原地下水作为地貌形成的重要因素的可行性。这项研究的结果将与青藏高原的研究有许多相似之处，在那里进行类似的研究将受到暴露问题的阻碍。这项研究将对教育和人力资源产生影响。在康奈尔大学，这项研究的结果将成为地貌学、地球物理学和盆地分析等本科课程的组成部分。所有结果都将编入地理信息系统软件，并通过互联网向公众提供。这项研究也将作为两个康奈尔大学研究生的论文组成部分。

The common association of thrust belts with the slopes of the great mountain belts has resulted in the common assumption that topographic relief and surface shortening are intrinsically linked. For example, many of the world's great mountain belts are doubly vergent, with well-developed thrust belts facing away from the interior of the orogen. However, in some key cases, significant topographic relief has developed in the absence of major faulting. These orogenic scale monoclines and their along-strike discontinuities have the potential to elucidate crustal mechanical and rheological controls on continental orogenesis. An exceptional example of an orogenic-scale monocline occurs along the western border of the Altiplano-Puna plateau of the central Andes. Although climate, and in particular precipitation, has a strong influence on the morphology of a mountain belt, in this region the climatic input is minimized because it is one of the driest places on Earth. The profound lack of precipitation causes the landscape to evolve extremely slowly and extend the preservation potential of landforms and surfaces from the thousands of years typical of mountain belts into millions of years. Therefore, the western edge of the plateau's morphology reflects a nearly pure tectonic signal, making it the most logical starting point for studies aimed at improving our understanding of continental plateau formation and orogenesis. A chronologic framework for the Miocene to present uplift of the Andean monocline will be derived from investigation of: 1) the geometric relationships between strata accumulating in sedimentary basins at the toe of the monocline, and 2) estimations of the degree of rotation of stream paleo-gradients in a set of drainages which are deeply incised into the monocline surface. Paleo-gradients will be determined by correlation and high accuracy surveying of terrace surfaces preserved in stream valleys. Extensive volcanism and large-volume ignimbrite eruptions are well distributed throughout the Neogene rock record, so that existing chronologic constraints can be improved upon by identification and collection of volcanic material for dating. The Atacama and Tamarugal Basins are ideal field areas in which to conduct the stratigraphic research in both outcrop and seismic. Both basins lie at the foot of the monocline and are hydrologically closed. Therefore, they preserve complete Neogene depositional histories. The Atacama Basin contains an especially valuable record because it lies within the largest along-strike anomaly in the monocline. Determining if a genetic link exists between the basin and the deflection of the monocline (temporally and spatially) will be an important research focus, as it may yield insight into processes fundamental to plateau uplift. This study is extremely timely and has the potential to be an excellent contribution to the understanding of surface processes, orogenesis and plateau uplift. The outcomes of this work will advance the present state of knowledge concerning the causes of plateau uplift by testing whether monocline warping is synchronous with deformation on the opposite side of the orogen, as expressed in the Sub-Andean belt and Eastern Cordillera. It will also test the significance of large topographic anomalies in otherwise continuous mountain-fronts. This study will explore the feasibility of plateau-derived groundwater as a substantial factor in landform genesis. The results of this study will contain many parallels to research on the Tibetan Plateau, where performing similar studies would be hampered by exposure problems. This research will have educational and human resource impacts. At Cornell University, results from this study will become components of undergraduate courses in geomorphology, geophysics and basin analysis. All results will be cataloged in GIS software and available to the public via the internet. This research will also serve as thesis components for two Cornell graduate students.