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

冲断带与大山带斜坡的共同联系导致了一个共同的假设，即地形起伏和地表缩短是内在联系的。例如，世界上许多伟大的山脉带都是双重陡峭的，发育良好的冲断带背对着造山带的内部。然而，在一些关键情况下，在没有重大断层的情况下，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面有可能阐明地壳对大陆造山作用的力学和流变学控制。沿安第斯山脉中部阿尔蒂普诺-普纳高原的西部边界出现了一个造山带规模的单斜构造的特例。虽然气候，特别是降水，对山脉地带的形态有很大的影响，但在这个地区，气候输入最少，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，地貌和地表的保存潜力从典型的山脉地带的数千年延长到数百万年。因此，高原西缘的形态反映了一种近乎纯粹的构造信号，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最合理的研究起点。通过对以下方面的研究，将得出中新世至今安第斯单斜隆升的年代学格架：1)单斜底部沉积盆地中累积的地层之间的几何关系；2)深切入单斜表面的一组水系中河流古梯度的旋转度估计。将通过对比和高精度测量保留在溪谷中的阶地表面来确定古梯度。广泛的火山作用和大量的褐沸石喷发分布在新近纪岩石记录中，因此现有的年代学限制可以通过识别和收集用于测年的火山物质来改善。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区域。这两个盆地都位于单斜层脚下，在水文上是封闭的。因此，它们保存了完整的新近系沉积史。阿塔卡马盆地包含一项特别有价值的记录，因为它位于单斜带中最大的沿走向异常范围内。确定盆地和单斜层的偏转(在时间和空间上)之间是否存在遗传联系将是一个重要的研究重点，因为这可能有助于洞察高原隆升的基本过程。这项研究非常及时，有可能对理解地表过程、造山作用和高原隆升做出极大贡献。这项工作的结果将通过测试单斜翘曲是否与造山带相反一侧的形变同步(如次安第斯带和东科迪莱拉所表示的)来推进关于高原隆升原因的现有认识。它还将测试在其他连续的山前地区出现的大型地形异常的重要性。这项研究将探索高原地下水作为地貌成因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，在青藏高原进行类似的研究将因暴露问题而受阻。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本科课程的组成部分。所有结果将在地理信息系统软件中编目，并通过互联网向公众提供。这项研究也将作为康奈尔大学两名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.