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，使人们普遍认为地形起伏和地表缩短具有内在联系。例如，世界上许多伟大的山带都是双重边缘的，具有发育良好的逆冲带，背对着造山带内部。然而，在一些关键的情况下，在没有大断层的情况下，明显的地形起伏已经形成。这些造山尺度单斜及其沿走向不连续面有可能阐明地壳力学和流变学对大陆造山作用的控制。在安第斯山脉中部的Altiplano-Puna高原的西部边界出现了一个造山规模的单斜的例外例子。虽然气候，特别是降水，对山带的形态有很大的影响，但在这个地区，由于它是地球上最干燥的地方之一，气候的影响最小。严重缺乏降水导致景观演变极其缓慢，并将地貌和地表的保存潜力从典型的山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个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认识的研究的最合乎逻辑的起点。中新世出现安第斯单斜隆起的年代学框架将通过以下研究得出：1)单斜脚尖沉积盆地中地层聚集之间的几何关系；2)深切入单斜表面的一组流域中河流古梯度旋转程度的估计。古梯度将通过对溪谷中保存的阶地面进行对比和高精度测量来确定。广泛的火山活动和大体积的火成岩喷发分布在整个新近系岩石记录中，因此可以通过火山物质的鉴定和收集来改善现有的年代学限制。阿塔卡马盆地和塔玛鲁戛尔盆地是开展露头和地震地层学研究的理想地区。两个盆地都位于单斜山脚，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个特别有价值的记录，因为它位于单斜中最大的沿走向异常内。确定盆地与单斜变形之间是否存在遗传联系（时间和空间上）将是一个重要的研究重点，因为它可能有助于深入了解高原隆起的基本过程。这项研究非常及时，有可能对了解地表作用、造山作用和高原隆升作出重大贡献。这项工作的结果将通过测试单斜翘曲是否与造山带对面的变形同步，如亚安第斯带和东科迪勒拉所表达的，来推进目前关于高原隆起原因的知识水平。它还将测试大型地形异常在连续的山锋中的意义。本研究将探讨高原地下水作为地貌成因重要因素的可行性。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名康奈尔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.